U.S. patent application number 11/107359 was filed with the patent office on 2006-06-01 for method of making an ocular implant.
Invention is credited to Thomas A. Silvestrini.
Application Number | 20060113054 11/107359 |
Document ID | / |
Family ID | 36035711 |
Filed Date | 2006-06-01 |
United States Patent
Application |
20060113054 |
Kind Code |
A1 |
Silvestrini; Thomas A. |
June 1, 2006 |
Method of making an ocular implant
Abstract
A method of making a mask configured to improve the depth of
focus of an eye of a patient is provided. A substrate with a mask
forming feature is provided. The mask forming feature comprises a
forming surface that extends from an outer periphery. The forming
surface is centered on a central axis of the mask forming feature.
A release layer is formed on the forming surface. A mask layer is
formed such that the release layer is between the mask layer and
the substrate. The mask layer is formed of a biocompatible metal. A
surface of the mask layer opposite the release layer is configured
to not corrode. The mask layer is separated from the substrate.
Inventors: |
Silvestrini; Thomas A.;
(Alamo, CA) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET
FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Family ID: |
36035711 |
Appl. No.: |
11/107359 |
Filed: |
April 14, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11000562 |
Dec 1, 2004 |
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11107359 |
Apr 14, 2005 |
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Current U.S.
Class: |
164/46 ;
623/5.16 |
Current CPC
Class: |
C23C 16/01 20130101;
A61F 2/0059 20130101; A61F 2250/0014 20130101; A61F 2/15 20150401;
A61F 2240/001 20130101; C23C 14/0005 20130101; A61F 2/14
20130101 |
Class at
Publication: |
164/046 ;
623/005.16 |
International
Class: |
B22D 23/00 20060101
B22D023/00 |
Claims
1. A method of making a mask configured to improve the depth of
focus of an eye of a patient, the method comprising: providing a
substrate with a mask forming feature comprising a forming surface
extending from an outer periphery, the forming surface being
centered on a central axis of the mask forming feature, the forming
surface having a curved profile corresponding to the curvature of a
corneal layer of the eye; forming a mask layer of a biocompatible
metal on the substrate; configuring a surface of the mask layer to
not corrode; and separating the mask layer from the substrate.
2. The method of claim 1, further comprising forming a
non-reflective layer on the mask layer to darken the appearance of
the mask.
3. The method of claim 2, wherein the biocompatible metal is a
noble metal and the non-reflective layer comprises a carbon
layer.
4. The method of claim 1, wherein forming further comprises forming
at least a portion of the mask layer of a titanium alloy.
5. The method of claim 4, wherein the titanium alloy exhibits
super-elastic characteristics.
6. The method of claim 4, wherein the titanium alloy is
nitinol.
7. The method of claim 4, wherein the titanium alloy comprises
nickel and titanium.
8. The method of claim 4, wherein the mask layer is a first layer,
and configuring further comprises forming a second mask layer of a
second material that does not react chemically with the titanium
alloy.
9. The method of claim 8, wherein the second material is titanium
oxide.
10. The method of claim 8, wherein the second material is silicon
carbide.
11. The method of claim 1, wherein the surface of the mask is
configured to not corrode by forming the mask layer of a
biocompatible metal that does not corrode when implanted in the
body.
12. The method of claim 1, wherein forming the mask layer further
comprises forming at least a portion of the mask layer of gold.
13. The method of claim 1, wherein forming the mask layer further
comprises forming at least a portion of the mask layer of
palladium.
14. The method of claim 1, wherein forming the mask layer further
comprises forming at least a portion of the mask layer of
platinum.
15. The method of claim 1, wherein forming the mask layer further
comprises forming at least a portion of the mask layer of
tantalum.
16. The method of claim 1, wherein forming the mask layer further
comprises forming at least a portion of the mask layer of
titanium.
17. The method of claim 1, wherein forming the mask layer further
comprises sputtering the mask layer.
18. The method of claim 1, wherein forming the mask layer further
comprises electro-depositing the mask layer.
19. The method of claim 1, wherein the forming surface is an
annular surface that extends from the outer periphery to an inner
periphery of the mask forming feature.
20. The method of claim 1, further comprising removing a central
portion of the mask layer to form an aperture in the mask
layer.
21. A method of making a mask configured to improve the depth of
focus of an eye of a patient, the method comprising: providing a
substrate with a mask forming feature comprising a forming surface
centered on a central axis of the mask forming feature; forming a
release layer on the forming surface; forming a mask layer of a
biocompatible metal such that the release layer is between the mask
layer and the substrate; configuring a surface of the mask layer
opposite the release layer to not corrode; and separating the mask
layer from the substrate.
22. A method of making a mask configured be implanted in a cornea
of an eye of a patient to improve the depth of focus of the
patient, the mask being disposed about a visual axis of the eye
extending through a pupil of the eye when applied, the method
comprising: providing a substrate with a mask forming feature
comprising an annular surface extending between an inner periphery
and an outer periphery, the annular surface being centered on a
central axis of the mask forming feature; forming at least a
portion of the mask by depositing a mask layer of a biocompatible
metal on the substrate; configuring the mask to be inert; and
separating the mask layer from the substrate.
23. The method of claim 22, wherein the mask is configured to be
inert by forming the mask layer of a noble metal.
24. The method of claim 22, further comprising forming a cosmetic
layer on an anterior surface of the mask such that the anterior
surface blends in with the pupil.
25. The method of claim 24, wherein the biocompatible metal is a
noble metal and the cosmetic layer is carbon.
26. The method of claim 22, wherein the mask is configured to be
inert by forming a cosmetic layer on an anterior surface of the
mask layer, at least one of the mask layer and the cosmetic layer
being selected such that there is substantially no galvanic
potential between the mask layer and the cosmetic layer.
27. The method of claim 26, wherein the mask layer is formed of an
alloy comprising nickel and titanium and the cosmetic layer is
formed of silicon carbide.
28. The method of claim 26, wherein the mask layer is formed of an
alloy comprising nickel and titanium and the cosmetic layer is
formed of titanium oxide.
29. The method of claim 22, wherein forming the mask layer further
comprises sputtering the mask layer.
30. The method of claim 22, wherein forming the mask layer further
comprises electro-depositing the mask layer.
31. The method of claim 22, wherein forming comprises forming the
mask layer with a plurality of pores.
32. The method of claim 31, further comprising configuring the
substrate to cause pore formation when the mask layer is
formed.
33. The method of claim 31, wherein the mask layer is formed by
electro-deposition and the density of pores is a function of an
electro-deposition rate.
34. The method of claim 22, wherein the substrate includes a
plurality of mask forming features and forming the mask layer
further comprises forming at least a portion of a first mask and at
least a portion of a second mask.
35. The method of claim 34, further comprising separating the first
mask portion from the second mask portion.
36. A mask configured to improve the depth of focus in an eye of a
patient comprising: a posterior layer formed of a biocompatible
metal; and a cosmetic layer.
37. The mask of claim 36, wherein the cosmetic layer is a
non-reflective layer
38. The mask of claim 37, wherein the cosmetic layer darkens the
appearance of the mask.
39. The mask of claim 36, wherein the biocompatible metal is a
noble metal and the cosmetic layer comprises a carbon layer.
40. The mask of claim 36, wherein the biocompatible metal comprises
a titanium alloy.
41. The mask of claim 40, wherein the titanium alloy exhibits
super-elastic characteristics.
42. The mask of claim 40, wherein the titanium alloy is
nitinol.
43. The mask of claim 40, wherein the titanium alloy comprises
nickel and titanium.
44. The mask of claim 40, wherein the posterior layer is a first
layer, and the cosmetic layer is formed of a material that does not
react chemically with the titanium alloy.
45. The mask of claim 44, wherein the cosmetic layer comprises
titanium oxide.
46. The mask of claim 44, wherein the cosmetic layer comprises
silicon carbide.
47. The mask of claim 36, wherein the posterior layer is formed of
a biocompatible metal that does not corrode when implanted in the
body.
48. The mask of claim 36, wherein the posterior layer comprises
gold.
49. The mask of claim 36, wherein the posterior layer comprises
palladium.
50. The mask of claim 36, wherein the posterior layer comprises
platinum.
51. The mask of claim 36, wherein the posterior layer tantalum.
52. The mask of claim 36, wherein the posterior layer comprises
titanium.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation in part of U.S.
application Ser. No. 11/000,562, filed Dec. 1, 2004, the entire
contents of which is hereby expressly incorporated by reference
herein.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This application is directed to masks for improving the
depth of focus of an eye of a human patient. This application also
is directed to apparatuses and methods to produce masks that are
resistant to corrosion, or other decay or degradation when applied
to a patient.
[0004] 2. Description of the Related Art
[0005] Presbyopia, or the inability to clearly see objects up close
is a common condition that afflicts many adults over the age of 40.
Presbyopia diminishes the ability to see or read up close. Near
objects appear blurry and out of focus. Presbyopia may be caused by
defects in the focusing elements of the eye or the inability (due
to aging) of the ciliary muscles to contract and relax and thereby
control the shape of the lens in the eye.
[0006] The human eye functions by receiving light rays from an
object and bending, refracting, and focusing those rays. The
primary focusing elements of the human eye are the lens (also
referred to as the intraocular lens) and the cornea. Light rays
from an object are bent by the cornea, which is located in the
anterior part of the eye. The light rays subsequently pass through
the intraocular lens and are focused thereby onto the retina, which
is the primary light receiving element of the eye. From the retina,
the light rays are converted to electrical impulses, which are then
transmitted by the optic nerves to the brain.
[0007] Ideally, the cornea and lens bend and focus the light rays
in such a way that they converge at a single point on the retina.
Convergence of the light rays on the retina produces a focused
image. However, if the cornea or the lens are not functioning
properly, or are irregularly shaped, the images may not converge at
a single point on the retina. Similarly, the image may not converge
at a single point on the retina if the muscles in the eye can no
longer adequately control the lens. This condition is sometimes
described as loss of accommodation. In presbyopic patients, for
example, the light rays often converge at a point behind the
retina. To the patient, the resulting image is out of focus and
appears blurry.
[0008] Traditionally, vision improvement has been achieved by
prescribing eye glasses or contact lenses to the patient. Eye
glasses and contact lenses are shaped and curved to help bend light
rays and improve focusing of the light rays onto the retina of the
patient. However, some vision deficiencies, such as presbyopia, are
not adequately addressed by these approaches.
SUMMARY OF THE INVENTION
[0009] In one embodiment, a method is provided for making a mask
configured to improve the depth of focus of an eye of a patient. A
substrate is provided with a mask forming feature. The mask forming
feature comprises an annular surface that extends between an inner
periphery and an outer periphery. The annular surface is centered
on a central axis of the mask forming feature. The annular surface
has a curved profile between the inner periphery and the outer
periphery that corresponds to the curvature of a corneal layer of
the eye. A release layer is formed on the annular surface. A mask
layer of a biocompatible metal is formed such that the release
layer is between the mask layer and the substrate. The mask layer
is separated from the substrate.
[0010] In another embodiment, a method is provided for making a
mask that is configured to improve the depth of focus of an eye of
a patient. A substrate is provided with a mask forming feature. The
mask forming feature includes a forming surface that extends from
an outer periphery. The forming surface can be an annular surface
that extends between the outer periphery and an inner periphery.
The forming surface is centered on a central axis of the mask
forming feature. The forming surface has a curved profile
corresponding to the curvature of a corneal layer of the eye. A
mask layer is formed of a biocompatible metal on the substrate. A
surface of the mask layer is configured to not corrode. The mask
layer is separated from the substrate.
[0011] In another embodiment, a method of making a mask configured
to improve the depth of focus of an eye of a patient is provided. A
substrate with a mask forming feature is provided. The mask forming
feature comprises a forming surface that is centered on a central
axis of the mask forming feature. A release layer is formed on the
annular surface. A mask layer is formed such that the release layer
is between the mask layer and the substrate. The mask layer is
formed of a biocompatible metal. A surface of the mask layer
opposite the release layer is configured to not corrode. The mask
layer is separated from the substrate.
[0012] In another embodiment, a method of making a mask configured
be implanted in a cornea of an eye of a patient to improve the
depth of focus of the patient is provided. The mask is disposed
about a visual axis of the eye extending through a pupil of the eye
when applied. A substrate with a mask forming feature is provided.
The mask forming feature comprises an annular surface that extends
between an inner periphery and an outer periphery. The annular
surface is centered on a central axis of the mask forming feature.
At least a portion of the mask is formed by depositing a mask layer
of a biocompatible metal on the substrate. The mask is configured
to be inert. The mask layer is separated from the substrate.
[0013] In another embodiment, a mask is configured to improve the
depth of focus in an eye of a patient. The mask includes a
posterior layer formed of a biocompatible metal and a cosmetic
layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a plan view of the human eye.
[0015] FIG. 2 is a cross-sectional side view of the human eye.
[0016] FIG. 3 is a cross-sectional side view of the human eye of a
presbyopic patient wherein the light rays converge at a point
behind the retina of the eye.
[0017] FIG. 4 is a cross-sectional side view of a presbyopic eye
implanted with one embodiment of a mask wherein the light rays
converge at a point on the retina.
[0018] FIG. 5 is a plan view of the human eye with a mask applied
thereto.
[0019] FIG. 6 is a perspective view of one embodiment of a
mask.
[0020] FIG. 7 is a frontal plan view of an embodiment of a mask
with a hexagon-shaped pinhole like aperture.
[0021] FIG. 8 is a frontal plan view of an embodiment of a mask
with an octagon-shaped pinhole like aperture.
[0022] FIG. 9 is a frontal plan view of an embodiment of a mask
with an oval-shaped pinhole like aperture.
[0023] FIG. 10 is a frontal plan view of an embodiment of a mask
with a pointed oval-shaped pinhole like aperture.
[0024] FIG. 11 is a frontal plan view of an embodiment of a mask
with a star-shaped pinhole like aperture.
[0025] FIG. 12 is a frontal plan view of an embodiment of a mask
with a teardrop-shaped pinhole like aperture spaced above the true
center of the mask.
[0026] FIG. 13 is a frontal plan view of an embodiment of a mask
with a teardrop-shaped pinhole like aperture centered within the
mask.
[0027] FIG. 14 is a frontal plan view of an embodiment of a mask
with a teardrop-shaped pinhole like aperture spaced below the true
center of the mask.
[0028] FIG. 15 is a frontal plan view of an embodiment of a mask
with a square-shaped pinhole like aperture.
[0029] FIG. 16 is a frontal plan view of an embodiment of a mask
with a kidney-shaped oval pinhole like aperture.
[0030] FIG. 17 is a side view of an embodiment of a mask having
varying thickness.
[0031] FIG. 18 is a side view of another embodiment of a mask
having varying thickness.
[0032] FIG. 19 is a side view of an embodiment of a mask with a gel
to provide opacity to the lens.
[0033] FIG. 20 is frontal plan view of an embodiment of a mask with
a weave of polymeric fibers.
[0034] FIG. 21 is a side view of the mask of FIG. 20.
[0035] FIG. 22 is a frontal plan view of an embodiment of a mask
having regions of varying opacity.
[0036] FIG. 23 is a side view of the mask of FIG. 22.
[0037] FIG. 24 is a frontal plan view of an embodiment of a mask
that includes a centrally located pinhole like aperture and
radially extending slots emanating from the center to the periphery
of the mask.
[0038] FIG. 25 is a side view of the mask of FIG. 24.
[0039] FIG. 26 is a frontal plan view of an embodiment of a mask
that includes a central pinhole like aperture, surrounded by a
plurality of holes radially spaced from the pinhole like aperture
and slots extending radially spaced from the holes and extending to
the periphery of the mask.
[0040] FIG. 27 is a side view of the mask of FIG. 26.
[0041] FIG. 28 is a frontal plan view of an embodiment of a mask
that includes a central pinhole like aperture, a region that
includes a plurality of holes radially spaced from the aperture,
and a region that includes rectangular slots spaced radially from
the holes.
[0042] FIG. 29 is a side view of the mask of FIG. 28.
[0043] FIG. 30 is a frontal plan view of an embodiment of a mask
that includes a non-circular pinhole like aperture, a first set of
slots radially spaced from the aperture, and a region that includes
a second set of slots extending to the periphery of the mask and
radially spaced from the first set of slots.
[0044] FIG. 31 is a side view of the mask of FIG. 30.
[0045] FIG. 32 is a frontal plan view of an embodiment of a mask
that includes a central pinhole like aperture and a plurality of
holes radially spaced from the aperture.
[0046] FIG. 33 is a side view of the mask of FIG. 32.
[0047] FIG. 34 is an embodiment of a mask that includes two
semi-circular mask portions.
[0048] FIG. 35 is an embodiment of a mask including two half-moon
shaped portions.
[0049] FIG. 36 is an embodiment of a mask that includes a half-moon
shaped region and a centrally-located pinhole like aperture.
[0050] FIG. 37 is an enlarged, diagrammatic view of an embodiment
of a mask that includes particulate structure adapted for
selectively controlling light transmission through the mask in a
low light environment.
[0051] FIG. 38 is a view of the mask of FIG. 37 in a bright light
environment.
[0052] FIG. 39 is an embodiment of a mask that includes a barcode
formed on the annular region of the mask.
[0053] FIG. 40 is another embodiment of a mask that includes
connectors for securing the mask within the eye.
[0054] FIG. 41 is a plan view of an embodiment of a mask made of a
spiraled fibrous strand.
[0055] FIG. 42 is a plan view of the mask of FIG. 41 being removed
from the eye.
[0056] FIG. 43 is a cross-sectional view similar to that of FIG. 2,
but showing certain axes of the eye.
[0057] FIG. 44A illustrates a single-target fixation method for
aligning an eye with the optical axis of an ophthalmic
instrument.
[0058] FIG. 44B illustrates another single-target fixation method
for aligning an eye with the optical axis of an ophthalmic
instrument.
[0059] FIG. 45A shows an apparatus for projecting a target onto an
optical axis at an infinite distance.
[0060] FIG. 45B shows an apparatus for projecting a target onto an
optical axis at a finite distance.
[0061] FIG. 46 illustrates a dual-target fixation method.
[0062] FIG. 47 shows an apparatus with which two targets can be
projected simultaneously by the same projection lens to provide
fixation targets at a large distance (such as infinity) and a
shorter (finite) distance.
[0063] FIG. 48 shows another embodiment of an apparatus for
combining two targets to project them simultaneously at different
axial distances.
[0064] FIG. 49A shows an example of a dual target pattern as viewed
by the patient when the target patterns are aligned.
[0065] FIG. 49B shows the dual target pattern of FIG. 49A when the
patterns are offset.
[0066] FIG. 50A shows an example of another dual target pattern as
viewed by the patient when the target patterns are aligned.
[0067] FIG. 50B shows the dual target pattern of FIG. 50A when the
target patterns are offset.
[0068] FIG. 51 shows one embodiment of an apparatus configured to
locate the visual axis of an eye of a patient by aligning the axis
with an axis of the apparatus.
[0069] FIG. 52 is a flow chart illustrating one method of screening
a patient for the use of a mask.
[0070] FIGS. 53A-53C show a mask, similar to those described
herein, inserted beneath an epithelium sheet of a cornea.
[0071] FIGS. 54A-54C show a mask, similar to those described
herein, inserted beneath a Bowman's membrane of a cornea.
[0072] FIG. 55 is a schematic diagram of one embodiment of a
surgical system configured to locate the visual axis of a patient's
eye by aligning the visual axis with an axis of the system.
[0073] FIG. 55A is a perspective view of another embodiment of a
dual target fixation target.
[0074] FIG. 55B is a top view of the fixation target of FIG. 55A
showing the first target.
[0075] FIG. 55C is a top view of the fixation target of FIG. 55A
showing the second target.
[0076] FIG. 56 is a top view of another embodiment of a surgical
system that includes an alignment device and a clamp configured to
couple the alignment device with a surgical viewing device.
[0077] FIG. 57 is a perspective view of the alignment device shown
in FIG. 56.
[0078] FIG. 58 is a top view of the alignment device shown in FIG.
57.
[0079] FIG. 59 is a schematic view of internal components of the
alignment device of FIG. 57.
[0080] FIG. 60 is a top view of another embodiment of a mask
configured to increase depth of focus.
[0081] FIG. 60A is an enlarged view of a portion of the view of
FIG. 60.
[0082] FIG. 61A is a cross-sectional view of the mask of FIG. 60A
taken along the section plane 61-61.
[0083] FIG. 61B is a cross-sectional view similar to FIG. 61A of
another embodiment of a mask.
[0084] FIG. 61C is a cross-sectional view similar to FIG. 61A of
another embodiment of a mask.
[0085] FIG. 62A is a graphical representation of one arrangement of
holes of a plurality of holes that may be formed on the mask of
FIG. 60.
[0086] FIG. 62B is a graphical representation of another
arrangement of holes of a plurality of holes that may be formed on
the mask of FIG. 60.
[0087] FIG. 62C is a graphical representation of another
arrangement of holes of a plurality of holes that may be formed on
the mask of FIG. 60.
[0088] FIG. 63A is an enlarged view similar to that of FIG. 60A
showing a variation of a mask having non-uniform size.
[0089] FIG. 63B is an enlarged view similar to that of FIG. 60A
showing a variation of a mask having a non-uniform facet
orientation.
[0090] FIG. 64 is a top view of another embodiment of a mask having
a hole region and a peripheral region.
[0091] FIG. 65 is a cross-sectional view of an eye illustrating a
treatment of a patient wherein a flap is opened to place an implant
and a location is marked for placement of the implant.
[0092] FIG. 65A is a partial plan view of the eye of FIG. 65
wherein an implant has been applied to a corneal flap and
positioned with respect to a ring.
[0093] FIG. 66 is a cross-sectional view of an eye illustrating a
treatment of a patient wherein a pocket is created to place an
implant and a location is marked for placement of the implant.
[0094] FIG. 66A is a partial plan view of the eye of FIG. 66
wherein an implant has been positioned in a pocket and positioned
with respect to a ring.
[0095] FIG. 67A is a schematic diagram of a substrate useful in a
making an ocular implant;
[0096] FIG. 67B is a schematic diagram illustrating a portion of a
method of making an ocular implant using the substrate of FIG. 67A
wherein a release layer is formed on the substrate;
[0097] FIG. 67C is a schematic diagram illustrating a portion of a
method of making an ocular implant using the substrate of FIG. 67A
wherein a release layer and a material layer are formed on the
substrate;
[0098] FIG. 67D is a schematic diagram illustrating a portion of a
method of making an ocular implant using the substrate of FIG. 67A
wherein an ocular implant is released from the substrate by a
suitable method.
[0099] FIG. 68 is a perspective view of a mask with a broken-out
section, the mask being configured to not corrode.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0100] This application is directed to masks for improving the
depth of focus of an eye of a patient using pin-hole imaging and
methods and apparatuses for making such masks. The masks may be
applied to the eye in any manner and in any location, e.g., as an
implant in the cornea (sometimes referred to as a "corneal inlay").
As discussed further below, some methods for making such masks
employ techniques that deposit thin films of material. The
materials used to make the mask can be metals that are selected or
configured for long-term or permanent implantation. Some metals are
subject to processes, such as corrosion, that can degrade a mask
over time. As discussed further below, the mask can be formed of a
material that is stable, e.g., one that is not subject to such
processes or that substantially resists such processes. In some
embodiments, the mask is formed of a material that is selected or
configured to be inert, e.g., to not degrade due to physical or
chemical processes such as corrosion induced by a galvanic reaction
or otherwise. In other embodiments, masks can be formed that
combine materials that are susceptible to corrosion with materials
that reduce or eliminate the likelihood that corrosion will occur
as a result of, for example, a galvanic reaction. These masks can
be produced by vapor deposition, thin film sputtering,
electro-depositing and other techniques amenable to batch
processing.
I. Overview of Pin-Hole Vision Correction
[0101] A mask that has a pinhole aperture may be used to improve
the depth of focus of a human eye. As discussed above, presbyopia
is a problem of the human eye that commonly occurs in older human
adults wherein the ability to focus becomes limited to inadequate
range. FIGS. 1-6 illustrate how presbyopia interferes with the
normal function of the eye and how a mask with a pinhole aperture
mitigates the problem.
[0102] FIG. 1 shows the human eye, and FIG. 2 is a side view of the
eye 10. The eye 10 includes a cornea 12 and an intraocular lens 14
posterior to the cornea 12. The cornea 12 is a first focusing
element of the eye 10. The intraocular lens 14 is a second focusing
element of the eye 10. The eye 10 also includes a retina 16, which
lines the interior of the rear surface of the eye 10. The retina 16
includes the receptor cells which are primarily responsible for the
sense of vision. The retina 16 includes a highly sensitive region,
known as the macula, where signals are received and transmitted to
the visual centers of the brain via the optic nerve 18. The retina
16 also includes a point with particularly high sensitivity 20,
known as the fovea. As discussed in more detail in connection with
FIG. 8, the fovea 20 is slightly offset from the axis of symmetry
of the eye 10.
[0103] The eye 10 also includes a ring of pigmented tissue known as
the iris 22. The iris 22 includes smooth muscle for controlling and
regulating the size of an opening 24 in the iris 22, which is known
as the pupil. An entrance pupil 26 is seen as the image of the iris
22 viewed through the cornea 12 (See FIG. 7). A central point of
the entrance pupil 28 is illustrated in FIG. 7 and will be
discussed further below.
[0104] The eye 10 resides in an eye-socket in the skull and is able
to rotate therein about a center of rotation 30.
[0105] FIG. 3 shows the transmission of light through the eye 10 of
a presbyotic patient. Due to either an aberration in the cornea 12
or the intraocular lens 14, or loss of muscle control, light rays
32 entering the eye 10 and passing through the cornea 12 and the
intraocular lens 14 are refracted in such a way that the light rays
32 do not converge at a single focal point on the retina 16. FIG. 3
illustrates that in a presbyopic patient, the light rays 32 often
converge at a point behind the retina 16. As a result, the patient
experiences blurred vision.
[0106] Turning now to FIG. 4, there is shown the light transmission
through the eye 10 to which a mask 34 has been applied. The mask 34
can be made by any suitable apparatus or method. Some advantageous
methods form the mask 34 of a material that is at least partially
opaque and very stable in the normal environment in which the mask
34 is deployed. For example, it is desired that the mask 34 be able
to survive many years of exposure to ultraviolet (UV) light. Thus,
in some embodiments, the mask is made of a UV stable material. A
variety of UV stable materials can be used to form the mask 34.
Preferably the UV stable material has a high degree of
biocompatibility because, as discussed below, the mask 34 is
implanted in the eye 10 in some techniques. Some specific examples
of methods of making the mask 34 are discussed below in connection
with FIGS. 67a-67d and with variations of such processes.
[0107] The mask 34 is shown implanted in the cornea 12 in FIG. 4.
However, as discussed below, it will be understood that the mask 34
can be, in various modes of application, implanted in the cornea 12
(as shown), used as a contact lens placed over the cornea 12,
incorporated in the intraocular lens 14 (including the patient's
original lens or an implanted lens), or otherwise positioned on or
in the eye 10. In the illustrated embodiment, the light rays 32
that pass through the mask 34, the cornea 12, and the lens 14
converge at a single focal point on the retina 16. The light rays
32 that would not converge at the single point on retina 16 are
blocked by the mask 34. As discussed below, it is desirable to
position the mask 34 on the eye 10 so that the light rays 32 that
pass through the mask 34 converge at the fovea 20.
[0108] Turning now to FIG. 6, there is shown one embodiment of the
mask 34. As seen, the mask 34 preferably includes an annular region
36 surrounding a pinhole opening or aperture 38 substantially
centrally located on the mask 34. The pinhole aperture 38 is
generally located around a central axis 39, referred to herein as
the optical axis of the mask 34. The pinhole aperture 38 preferably
is in the shape of a circle. It has been reported that a circular
aperture, such as the aperture 38 may, in some patients, produce a
so-called "halo effect" where the patient perceives a shimmering
image around the object being viewed. Accordingly, it may be
desirable to provide an aperture 38 in a shape that diminishes,
reduces, or completely eliminates the so-called "halo effect."
II. Masks Employing Pin-Hole Correction
[0109] FIGS. 7-42 illustrate a variety of embodiments of masks that
can improve the vision of a patient with presbyopia. The masks
described in connection with FIGS. 7-42 are similar to the mask 34,
except as set forth below. Accordingly, the masks described in
connection with FIGS. 7-42 can be used and applied to the eye 10 of
a patient in a similar fashion to the mask 34. Also, like the mask
34, the masks 7-42 can be formed by the processes disclosed in
connection with FIGS. 67a-67d and with variations of such
processes.
[0110] FIG. 7 shows an embodiment of a mask 34a that includes an
aperture 38a formed in the shape of a hexagon. FIG. 8 shows another
embodiment of a mask 34b that includes an aperture 38b formed in
the shape of an octagon. FIG. 9 shows another embodiment of a mask
34c that includes an aperture 38c formed in the shape of an oval,
while FIG. 10 shows another embodiment of a mask 34d that includes
an aperture 38d formed in the shape of a pointed oval. FIG. 11
shows another embodiment of a mask 34e wherein the aperture 38e is
formed in the shape of a star or starburst.
[0111] FIGS. 12-14 illustrate further embodiments that have
tear-drop shaped apertures. FIG. 12 shows a mask 34f that has a
tear-drop shaped aperture 38f that is located above the true center
of the mask 34f. FIG. 13 shows a mask 34g that has a tear-drop
shaped aperture 38g that is substantially centered in the mask 34g.
FIG. 14 shows a mask 34h that has a tear-drop shaped aperture 38h
that is below the true center of the mask 34h. FIGS. 12-14
illustrate that the position of aperture can be tailored, e.g.,
centered or off-center, to provide different effects. For example,
an aperture that is located below the true center of a mask
generally will allow more light to enter the eye because the upper
portion of the aperture 34 will not be covered by the eyelid of the
patient. Conversely, where the aperture is located above the true
center of the mask, the aperture may be partially covered by the
eyelid. Thus, the above-center aperture may permit less light to
enter the eye.
[0112] FIG. 15 shows an embodiment of a mask 34i that includes an
aperture 38i formed in the shape of a square. FIG. 16 shows an
embodiment of a mask 34j that has a kidney-shaped aperture 38j. It
will be appreciated that the apertures shown in FIGS. 7-16 are
merely exemplary of non-circular apertures. Other shapes and
arrangements may also be provided and are within the scope of the
present invention.
[0113] The mask 34 preferably has a constant thickness, as
discussed below. However, in some embodiments, the thickness of the
mask may vary between the inner periphery (near the aperture 38)
and the outer periphery. FIG. 17 shows a mask 34k that has a
gradually decreasing thickness from the inner periphery to the
outer periphery. FIG. 18 shows a mask 34l that has a gradually
increasing thickness from the inner periphery to the outer
periphery. Other cross-sectional profiles are also possible.
[0114] The annular region 36 is at least partially and preferably
completely opaque. The opacity of the annular region 36 prevents
light from being transmitted through the mask 32 (as generally
shown in FIG. 4). Opacity of the annular region 36 may be achieved
in any of several different ways.
[0115] For example, in one embodiment, the material used to make
mask 34 may be naturally opaque. Alternatively, the material used
to make the mask 34 may be substantially clear, but treated with a
dye or other pigmentation agent to render region 36 substantially
or completely opaque. In still another example, the surface of the
mask 34 may be treated physically or chemically (such as by
etching) to alter the refractive and transmissive properties of the
mask 34 and make it less transmissive to light.
[0116] In still another alternative, the surface of the mask 34 may
be treated with a particulate deposited thereon. For example, the
surface of the mask 34 may be deposited with particulate of
titanium, gold or carbon to provide opacity to the surface of the
mask 34. In another alternative, the particulate may be
encapsulated within the interior of the mask 34, as generally shown
in FIG. 19. Finally, the mask 34 may be patterned to provide areas
of varying light transmissivity, as generally shown in FIGS. 24-33,
which are discussed in detail below.
[0117] Turning to FIG. 20, there is shown a mask 34m formed or made
of a woven fabric, such as a mesh of polyester fibers. The mesh may
be a cross-hatched mesh of fibers. The mask 34m includes an annular
region 36m surrounding an aperture 38m. The annular region 36m
comprises a plurality of generally regularly positioned apertures
36m in the woven fabric that allow some light to pass through the
mask 34m. The amount of light transmitted can be varied and
controlled by, for example, moving the fibers closer together or
farther apart, as desired. Fibers more densely distributed allow
less light to pass through the annular region 36m. Alternatively,
the thickness of fibers can be varied to allow more or less light
through the openings of the mesh. Making the fiber strands larger
results in the openings being smaller.
[0118] FIG. 22 shows an embodiment of a mask 34n that includes an
annular region 36n that has sub-regions with different opacities.
The opacity of the annular region 36n may gradually and
progressively increased or decreased, as desired. FIG. 22 shows one
embodiment where a first area 42 closest to an aperture 38n has an
opacity of approximately 60%. In this embodiment, a second area 44,
which is outlying with respect to the first area 42, has a greater
opacity, such as 70%. In this embodiment, a third area 46, which is
outlying with respect to the second area 42, has an opacity of
between 85 to 100%. The graduated opacity of the type described
above and shown in FIG. 22 is achieved in one embodiment by, for
example, providing different degrees of pigmentation to the areas
42, 44 and 46 of the mask 34n. In another embodiment, light
blocking materials of the type described above in variable degrees
may be selectively deposited on the surface of a mask to achieve a
graduated opacity.
[0119] In another embodiment, the mask may be formed from
co-extruded rods made of material having different light
transmissive properties. The co-extruded rod may then be sliced to
provide disks for a plurality of masks, such as those described
herein.
[0120] FIGS. 24-33 show examples of masks that have been modified
to provide regions of differing opacity. For example, FIG. 24 shows
a mask 34o that includes an aperture 38o and a plurality of cutouts
48 in the pattern of radial spokes extending from near the aperture
38o to an outer periphery 50 of the mask 34o. FIG. 24 shows that
the cutouts 48 are much more densely distributed about a
circumference of the mask near aperture 38o than are the cutouts 48
about a circumference of the mask near the outer periphery 50.
Accordingly, more light passes through the mask 34o nearer aperture
38o than near the periphery 50. The change in light transmission
through the mask 34o is gradual.
[0121] FIGS. 26-27 show another embodiment of a mask 34p. The mask
34p includes an aperture 38p and a plurality of circular cutouts
52p, and a plurality of cutouts 54p. The circular cutouts 52p are
located proximate the aperture 38p. The cutouts 54p are located
between the circular cutouts 52p and the periphery 50p. The density
of the circular cutouts 52p generally decreases from the near the
aperture 38p toward the periphery 50p. The periphery 50p of the
mask 34p is scalloped by the presence of the cutouts 54, which
extend inward from the periphery 50p, to allow some light to pass
through the mask at the periphery 50p.
[0122] FIGS. 28-29 show another embodiment similar to that of FIGS.
26-27 wherein a mask 34q includes a plurality of circular cutouts
52q and a plurality of cutouts 54q. The cutouts 54q are disposed
along the outside periphery 50q of the mask 34q, but not so as to
provide a scalloped periphery.
[0123] FIGS. 30 and 31 illustrate an embodiment of a mask 34r that
includes an annular region 36r that is patterned and an aperture
38r that is non-circular. As shown in FIG. 30, the aperture 38r is
in the shape of a starburst. Surrounding the aperture 38r is a
series of cutouts 54r that are more densely spaced toward the
aperture 38r. The mask 34r includes an outer periphery 50r that is
scalloped to provide additional light transmission at the outer
periphery 50r.
[0124] FIGS. 32 and 33 show another embodiment of a mask 34s that
includes an annular region 36s and an aperture 38s. The annular
region 36s is located between an outer periphery 50s of the mask
34s and the aperture 38s. The annular region 36s is patterned. In
particular, a plurality of circular openings 56s is distributed
over the annular region 36s of the mask 34s. It will be appreciated
that the density of the openings 56s is greater near the aperture
38s than near the periphery 50s of the mask 34s. As with the
examples described above, this results in a gradual increase in the
opacity of the mask 34s from aperture 38s to periphery 50s.
[0125] FIGS. 34-36 show further embodiments. In particular, FIG. 34
shows a mask 34t that includes a first mask portion 58t and a
second mask portion 60t. The mask portions 58t, 60t are generally
"C-shaped." As shown in FIG. 34, the mask portions 58t, 60t are
implanted or inserted such that the mask portions 58t, 60t define a
pinhole or aperture 38t.
[0126] FIG. 35 shows another embodiment wherein a mask 34u includes
two mask portions 58u, 60u. Each mask portion 58u, 60u is in the
shape of a half-moon and is configured to be implanted or inserted
in such a way that the two halves define a central gap or opening
62u, which permits light to pass therethrough. Although opening 62u
is not a circular pinhole, the mask portions 58u, 60u in
combination with the eyelid (shown as dashed line 64) of the
patient provide a comparable pinhole effect.
[0127] FIG. 36 shows another embodiment of a mask 34v that includes
an aperture 38v that is in the shape of a half-moon. As discussed
in more detail below, the mask 34v may be implanted or inserted
into a lower portion of the cornea 12 where, as described above,
the combination of the mask 34v and the eyelid 62 provides the
pinhole effect.
[0128] Other embodiments employ different ways of controlling the
light transmissivity through a mask. For example, the mask may be a
gel-filled disk, as shown in FIG. 19. The gel may be a hydrogel or
collagen, or other suitable material that is biocompatible with the
mask material and can be introduced into the interior of the mask.
The gel within the mask may include particulate 66 suspended within
the gel. Examples of suitable particulate are gold, titanium, and
carbon particulate, which, as discussed above, may alternatively be
deposited on the surface of the mask.
[0129] The material of the mask 34 may be any biocompatible
polymeric material. Where a gel is used, the material is suitable
for holding a gel. Examples of suitable materials for the mask 34
include the preferred polymethylmethacrylate or other suitable
polymers, such as polycarbonates and the like. Of course, as
indicated above, for non-gel-filled materials, a preferred material
may be a fibrous material, such as a Dacron mesh. Additional
techniques are discussed below whereby the masks discussed herein
can be formed of processes that deposit metal layers.
[0130] The mask 34 may also be made to include a medicinal fluid,
such as an antibiotic that can be selectively released after
application, insertion, or implantation of the mask 34 into the eye
of the patient. Release of an antibiotic after application,
insertion, or implantation provides faster healing of the incision.
The mask 34 may also be coated with other desired drugs or
antibiotics. For example, it is known that cholesterol deposits can
build up on the eye. Accordingly, the mask 34 may be provided with
a releasable cholesterol deterring drug. The drug may be coated on
the surface of the mask 34 or, in an alternative embodiment,
incorporated into the polymeric material (such as PMMA) from which
the mask 34 is formed.
[0131] FIGS. 37 and 38 illustrate one embodiment where a mask 34w
comprises a plurality of nanites 68. "Nanites" are small
particulate structures that have been adapted to selectively
transmit or block light entering the eye of the patient. The
particles may be of a very small size typical of the particles used
in nanotechnology applications. The nanites 68 are suspended in the
gel or otherwise inserted into the interior of the mask 34w, as
generally shown in FIGS. 37 and 38. The nanites 68 can be
preprogrammed to respond to different light environments.
[0132] Thus, as shown in FIG. 37, in a high light environment, the
nanites 68 turn and position themselves to substantially and
selectively block some of the light from entering the eye. However,
in a low light environment where it is desirable for more light to
enter the eye, nanites may respond by turning or be otherwise
positioned to allow more light to enter the eye, as shown in FIG.
38.
[0133] Nano-devices or nanites are crystalline structures grown in
laboratories. The nanites may be treated such that they are
receptive to different stimuli such as light. In accordance with
one aspect of the present invention, the nanites can be imparted
with energy where, in response to a low light and bright light
environments, they rotate in the manner described above and
generally shown in FIG. 38.
[0134] Nanoscale devices and systems and their fabrication are
described in Smith et al., "Nanofabrication," Physics Today,
February 1990, pp. 24-30 and in Craighead, "Nanoelectromechanical
Systems," Science, Nov. 24, 2000, Vol. 290, pp. 1532-1535, both of
which are incorporated by reference herein in their entirety.
Tailoring the properties of small-sized particles for optical
applications is disclosed in Chen et al. "Diffractive Phase
Elements Based on Two-Dimensional Artificial Dielectrics," Optics
Letters, Jan. 15, 1995, Vol. 20, No. 2, pp. 121-123, also
incorporated by reference herein in its entirety.
[0135] Masks 34 made in accordance with the present invention may
be further modified to include other properties. FIG. 39 shows one
embodiment of a mask 34x that includes a bar code 70 or other
printed indicia.
[0136] The masks described herein may be incorporated into the eye
of a patient in different ways. For example, as discussed in more
detail below in connection with FIG. 52, the mask 34 may be
provided as a contact lens placed on the surface of the eyeball 10.
Alternatively, the mask 34 may be incorporated in an artificial
intraocular lens designed to replace the original lens 14 of the
patient. Preferably, however, the mask 34 is provided as a corneal
implant or inlay, where it is physically inserted between the
layers of the cornea 12.
[0137] When used as a corneal implant, layers of the cornea 12 are
peeled away to allow insertion of the mask 34. Typically, the
optical surgeon (using a laser) cuts away and peels away a flap of
the overlying corneal epithelium. The mask 34 is then inserted and
the flap is placed back in its original position where, over time,
it grows back and seals the eyeball. In some embodiments, the mask
34 is attached or fixed to the eye 10 by support strands 72 and 74
shown in FIG. 40 and generally described in U.S. Pat. No.
4,976,732, incorporated by reference herein in its entirety.
[0138] In certain circumstances, to accommodate the mask 34, the
surgeon may be required to remove additional corneal tissue. Thus,
in one embodiment, the surgeon may use a laser to peel away
additional layers of the cornea 12 to provide a pocket that will
accommodate the mask 34. Application of the mask 34 to the cornea
12 of the eye 10 of a patient is described in greater detail in
connection with FIGS. 53A-54C.
[0139] Removal of the mask 34 may be achieved by simply making an
additional incision in the cornea 12, lifting the flap and removing
the mask 34. Alternatively, ablation techniques may be used to
completely remove the mask 34.
[0140] FIGS. 41 and 42 illustrate another embodiment of a mask 34y
that includes a coiled strand 80 of a fibrous or other material.
Strand 80 is coiled over itself to form the mask 34y, which may
therefore be described as a spiral-like mask. This arrangement
provides a pinhole or aperture 38y substantially in the center of
the mask 34y. The mask 34y can be removed by a technician or
surgeon who grasps the strand 80 with tweezers 82 through an
opening made in a flap of the cornea 12. FIG. 42 shows this removal
technique.
[0141] Further mask details are disclosed in U.S. Pat. No.
4,976,732, issued Dec. 11, 1990 and in U.S. Provisional Application
Ser. No. 60/473,824, filed May 28, 2003, both of which are
incorporated by reference herein in their entirety.
III. Methods of Applying Pinhole Aperture Devices
[0142] The various masks discussed herein can be used to improve
the vision of a presbyopic patient as well as that of patients with
other vision problems. The masks discussed herein can be deployed
in combination with a LASIK procedure, to eliminate the effects of
abrasions, aberrations, and divots in the cornea. It is also
believed that the masks disclosed herein can be used to treat
patients suffering from macular degeneration, e.g., by directing
light rays to unaffected portions of retina, thereby improving the
vision of the patient. Whatever treatment is contemplated, more
precise alignment of the central region of a mask with a pin-hole
aperture with the visual axis of the patient is believed to provide
greater clinical benefit to the patient.
A. Alignment of the Pinhole Aperture with the Patient's Visual
Axis
[0143] Alignment of the central region of the pinhole aperture 38,
in particular, the optical axis 39, of the mask 34 with the visual
axis of the eye 10 may be achieved in a variety of ways. As
discussed more fully below, such alignment may be achieved by
imaging two reference targets at different distances and effecting
movement of the patient's eye to a position where the images of the
first and second reference targets appear aligned as viewed by the
patient's eye. When the patient views the targets as being aligned,
the patient's visual axis is located.
[0144] FIG. 43 is a cross-sectional view of the eye 10, similar to
that shown in FIG. 1, indicating a first axis 1000 and a second
axis 1004. The first axis 1000 represents the visual axis, or line
of sight, of the patient and the second axis 1004 indicates the
axis of symmetry of the eye 10. The visual axis 1000 is an axis
that connects the fovea 20 and a target 1008. The visual axis 1000
also extends through the central point 28 of the entrance pupil 26.
The target 1008 is sometimes referred to herein as a "fixation
point." The visual axis 1000 also corresponds to the chief ray of
the bundle of rays emanating from the target 1008 that passes
through the pupil 22 and reaches the fovea 20. The axis of symmetry
1004 is an axis passing through the central point 28 of the
entrance pupil 26 and the center of rotation 30 of the eye 10. As
described above, the cornea 12 is located at the front of the eye
10 and, along with the iris 22, admits light into the eye 10. Light
entering the eye 10 is focused by the combined imaging properties
of the cornea 12 and the intraocular lens 14 (see FIGS. 2-3).
[0145] In a normal eye, the image of the target 1008 is formed at
the retina 16. The fovea 20 (the region of the retina 16 with
particularly high resolution) is slightly off-set from the axis of
symmetry 1004 of the eye 10. This visual axis 1000 is typically
inclined at an angle .theta. of about six (6) degrees to the axis
of symmetry 1004 of the eye 10 for an eye with a centered iris.
[0146] FIGS. 44A and 44B illustrate single-target fixation methods
for aligning an eye with an optical axis of an instrument also
referred to herein as an "instrument axis." In FIG. 44A, the eye 10
is shown looking into an aperture of a projection lens 1012. The
lens aperture is shown as the entire lens 1012. The projection lens
1012 reimages a reference target 1016 at an infinite distance,
producing a collimated beam 1020.
[0147] The reference target 1016 in FIG. 44A is shown reimaged at
an infinite distance, which is achieved by positioning the target
object at a distance 1024 equal to the focal length f of the lens
1012, i.e. the reference target 1016 is at the lens focal point. To
a first-order approximation, the relationship between the object
and the image distances for a lens of focal length f follows the
Gaussian equation (1/A)=(1/f)+(1/B) where B and A are respectively
the object and image distances measured from the lens center.
Because the illuminated target appears at an infinite distance as
viewed by the eye 10, individual light rays 1020a to 1020g are
parallel to each other.
[0148] FIG. 44A shows the eye 10 fixated on the reference target
1016 along a ray 1020c, which appears to come from the reference
target 1016 as imaged by the projection lens 1012. The eye 10 is
here decentered a distance 1028 from an optical axis 1032 of the
instrument, i.e., the instrument axis, which may be the central
axis of the lens 1012. This decentration of the eye 10 with respect
to the optical axis 1032 of the instrument does not affect fixation
to an infinitely distant image because all rays projected by the
lens 1012 are parallel. As such, in an instrument that relies on
fixation to a single target imaged at infinity, an eye can be
fixated on the target but still be off-center of the optical axis
of the instrument.
[0149] FIG. 44B is similar to FIG. 44A, except that a reference
target 1016' is located somewhat closer to the projection lens 1012
than is the reference target 1016 so that an image 1036 of the
reference target 1016' appears at a large but finite distance 1040
behind the lens 1012. As was the case in FIG. 44A, the eye 10 in
FIG. 44B is fixated on the reference target 1016' along a ray
1020c', which is decentered a distance 1028 from an optical axis
1032 of the instrument. However, the rays 1020a' to 1020g'
projected by the lens 1012 shown in FIG. 44B are seen to diverge as
if they originated at the image 1036 of the reference target 1016',
which is located on the optical axis 1032 of the lens 1012 at a
finite distance 1040 from the lens 1012. If the decentration of the
eye 10 (corresponding to the distance 1028) changes, the eye 10
must rotate somewhat about its center of rotation 30 in order to
fixate on the image 1036. The eye 10 in FIG. 44B is shown rotated
by some angle so as to align its visual axis 1000 with the
direction of propagation of ray 1020c'. Thus, in general, a
decentered eye fixated on a finite-distance target is not merely
off-center but is also angularly offset from the optical axis 1032
of the instrument.
[0150] FIG. 45A shows one embodiment of a projection lens 1012 used
to create an optical image at infinite distance, as was
schematically shown in FIG. 44A. The reference target 1016
typically is a back-illuminated pattern on a transparent glass
reticle 1044. The reference target 1016 is located at a distance
1024 on the lens' optical axis 1032 at the lens' focal point, i.e.
the reference target 1016 is located such that the distance 1024 is
equal to the distance f. A diffusing plate 1048 and a condensing
lens 1052 are used to ensure full illumination of the reference
target 1016 throughout the aperture of the projection lens 1012.
Light rays projected by the projection lens 1012 are substantially
parallel depending upon the degree of imaging perfection achieved
in the optical system. Assuming a well-corrected lens with small
aberrations, the image as observed through the aperture of the
projection lens 1012 will appear to be at infinity.
[0151] FIG. 45B shows a somewhat different optical system in which
a target 1016' is projected so that an image 1036 appears at a
large but finite distance 1040 behind the lens 1012, as was shown
schematically in FIG. 44B. The diffusing plate 1048 and the
condensing lens 1052 again are used to ensure that full
illumination of the target reference 112' is achieved throughout
the aperture of the projection lens 1012. In the system of FIG.
45B, the reference target 1016' is located at an object distance
1024', which is inside the focal point in accordance with the
aforementioned Gaussian equation. Thus, the object distance 1024'
is a distance that is less than the focal length f of the lens
1012'. The path of a typical light ray 1056 from the center of the
reference target 1016' is shown. If the eye 10 is aligned with this
ray 1056, the reference target 1016 is observed as if it were
located at the location of the image 1036, i.e. at a finite
distance. The ray 1056 would then be similar to ray 1020c' of FIG.
44B, and fixation of the eye 10 could be established as appropriate
for the given degree of decentration from the optical axis
1032.
[0152] FIG. 46 illustrates a fixation method whereby the
single-target fixation methods shown in FIGS. 44A and 44B are both
used simultaneously in a dual-target fixation system. With two
fixation targets 1016 and 1016' at different distances, the eye 10
will see angular disparity (parallax) between the target images
(i.e., they will not appear to be superimposed) if the eye is
decentered. The rays 1020a to 1020g of the infinite-distance target
1016 are parallel to one another, while the rays 1020a' to 1020g'
of the finite distance target 1016' diverge. The only rays of the
targets that coincide are rays 1020d and 10204d', which are
collinear along the optical axis 1032 of the instrument. Thus, the
eye 10 can be simultaneously fixated on both targets if the visual
axis, represented by the first axis 1000 of the eye 10, is centered
on the optical axis of the instrument, i.e. along the ray 1020d
(which is the same as 1020d'). Thus, when the visual axis of the
eye 10 lies on the optical axis 1032 of the apparatus, both images
are fixated.
[0153] FIG. 47 shows schematically an apparatus with which two
reticle patterns could be projected simultaneously by the same
projection lens to provide fixation targets 1016 and 1016' at a
large distance 1024 (such as infinity) and a shorter (finite)
distance 1024'. It is preferable that both fixation targets are at
relatively large distances so that only slight focus accommodation
of the eye 10 is required to compensate for these different
distances. By instructing the patient to move his or her eye
transversely with respect to the instrument axis until a visual
event occurs, e.g., angular displacement (parallax) between the
images is minimized, alignment of the eye 10 with the optical axis
1032 of the apparatus is facilitated. Providing two fixation
targets at different apparent distances will simplify accurate
alignment of the sighted eye with an ophthalmic apparatus in the
surgical procedures disclosed herein and in other similar surgical
procedures.
[0154] FIG. 48 shows another embodiment of an apparatus for
combining two fixation targets 1016 and 1016' to project them
simultaneously at different axial distances. A beamsplitter plate
or cube 1060 is inserted between the patterns and the projection
lens 1012 so each pattern can be illuminated independently. In the
embodiments of FIGS. 46 and 47, the targets 1016, 1016' can be
opaque lines seen against a light background, bright lines seen
against a dark background, or a combination of these forms.
[0155] FIG. 49A shows an example of a typical dual pattern as
viewed by the patient when the patterns are aligned, i.e. when the
patient's eye is aligned with the optical axis of the apparatus.
The dual pattern set in this embodiment comprises an opaque
fine-line cross 1064 seen against a broader bright cross 1068. FIG.
49B shows the same dual pattern set as shown in FIG. 49A, except
the patterns are offset, indicating that the eye 10 is decentered
with respect to the optical axis of the associated optical
instrument.
[0156] FIG. 50A shows an example of another dual pattern as viewed
by the patient when the patterns are aligned, i.e. when the
patient's eye is aligned with the optical axis of the ophthalmic
instrument. The dual pattern set in this embodiment comprises an
opaque circle 1072 seen against a bright circle 1076. The circle
1072 has a diameter that is greater than the diameter of the circle
1076. FIG. 50B shows the same dual pattern set as shown in FIG.
50A, except the patterns are offset, indicating that the eye 10 is
decentered with respect the optical axis of the associated optical
instrument. It is not necessary that the targets appear as crosses
or circles; patterns such as dots, squares, and other shapes and
patterns also can suffice.
[0157] In another embodiment, color is used to indicate when the
patient's eye is aligned with the optical axis of the apparatus.
For example, a dual color set can be provided. The dual color set
may comprise a first region of a first color and a second region of
a second color. As discussed above in connection with the dual
pattern sets, the patient visual axis is located when the first
color and the second color are in a particular position relative to
each other. This may cause a desired visual effect to the patient's
eye, e.g., when the first region of the first color is aligned with
the second region of the second color, the patient may observe a
region of a third color. For example, if the first region is
colored blue and the second region is colored yellow, the patient
will see a region of green. Additional details concerning locating
a patient's visual axis or line of sight are contained in U.S. Pat.
No. 5,474,548, issued Dec. 12, 1995, incorporated by reference
herein in its entirety.
[0158] FIG. 51 shows one embodiment of an ophthalmic instrument
1200 that can be used in connection with various methods described
herein to locate the visual axis of a patient. The instrument 1200
includes an optics housing 1202 and a patient locating fixture 1204
that is coupled with the optics housing 1202. The optics housing
1202 includes an optical system 1206 that is configured to project
two reticle patterns simultaneously to provide fixation targets at
a large distance, e.g., infinity, and a shorter, finite
distance.
[0159] In the illustrated embodiment, the optical system 1206 of
the instrument includes a first reference target 1208, a second
reference target 1210, and a projection lens 1212. The first and
second reference targets 1208, 1210 are imaged by the projection
lens 1212 along an instrument axis 1213, of the ophthalmic
instrument 1200. In one embodiment, the first reference target 1208
is formed on a first glass reticle 1214 located a first distance
1216 from the lens 1212 and the second target 1210 is formed on a
second glass reticle 1218 located a second distance 1220 from the
lens 1212. Preferably, the second distance 1220 is equal to the
focal length f of the lens 1212, as was discussed in connection
with FIG. 44A. As discussed above, positioning the second target
1210 at the focal length f of the lens 1212 causes the second
target 1210 to be imaged at an infinite distance from the lens
1212. The first distance 1216 preferably is less than the second
distance 1220. As discussed above, the first reference target 1208
is thereby imaged at a large but finite distance from the lens
1212. By positioning the first and second reference targets 1208,
1210 in this manner, the method set forth above for aligning the
eye 10 of the patient may be implemented with the ophthalmic
instrument 1200.
[0160] The optical system 1206 preferably also includes a light
source 1222 that marks the visual axis of the patient after the
visual axis has been located in the manner described above. In the
illustrated embodiment, the light source 1222 is positioned
separately from the first and second reference targets 1208, 1210.
In one embodiment, the light source 1222 is positioned at a ninety
degree angle to the instrument axis 1213 and is configured to
direct light toward the axis 1213. In the illustrated embodiment, a
beamsplitter plate or cube 1224 is provided between the first and
second reference targets 1208, 1210 and the patient to route light
rays emitted by the light source 1222 to the eye of the patient.
The beamsplitter 1224 is an optical component that reflects light
rays from the direction of the light source 1222, but permits the
light rays to pass through the beamsplitter along the instrument
axis 1213. Thus, light rays form the first and second reference
targets 1208, 1210 and from the light source 1222 may be propagated
toward the eye of the patient. Other embodiments are also possible.
For example, the beamsplitter 1224 could be replaced with a mirror
that is movable into and out of the instrument axis 1213 to
alternately reflect light from the light source 1222 to the eye or
to permit light from the first and second reference targets 1208,
1210 to reach the eye.
[0161] The patient locating fixture 1204 includes an elongate
spacer 1232 and a contoured locating pad 1234. The contoured
locating pad 1234 defines an aperture through which the patient may
look along the instrument axis 213. The spacer 1232 is coupled with
the optics housing 1202 and extends a distance 1236 between the
housing 1202 and the contoured locating pad 1234. In one
embodiment, the spacer 1232 defines a lumen 1238 that extends
between the contoured locating pads 1234 and the optics housing
1202. In some embodiments, the magnitude of the distance 1236 may
be selected to increase the certainty of the location of the
patient's visual axis. In some embodiments, it is sufficient that
the distance 1236 be a relatively fixed distance.
[0162] When the alignment apparatus 1200 is used, the patient's
head is brought into contact with the contoured locating pad 1234,
which locates the patient's eye 10 in the aperture at a fixed
distance from the first and second reference targets 1208, 1210.
Once the patient's head is positioned in the contoured locating pad
1234, the patient may move the eye 10 as discussed above, to locate
the visual axis. After locating the visual axis, the light source
1222 is engaged to emit light toward the eye 10, e.g., as reflected
by the beamsplitter 1224.
[0163] In the illustrated embodiment, at least some of the light
emitted by the light source 1222 is reflected by the beamsplitter
1224 along the instrument axis 1213 toward the patient's eye 10.
Because the visual axis of the eye 10 was previously aligned with
the instrument axis 1213, the light from the light source 1222
reflected by the beamsplitter 1224 is also aligned with the visual
axis of the eye 10.
[0164] The reflected light provides a visual marker of the location
of the patient's visual axis. The marking function of the light
source 1222 is particularly useful in connection with the methods,
described below, of applying a mask. Additional embodiments of
ophthalmic instruments embodying this technique are described below
in connection with FIGS. 55-59.
B. Methods of Applying a Mask
[0165] Having described a method for properly locating the visual
axis of the eye 10 of a patient and for visually marking the visual
axis, various methods for applying a mask to the eye will be
discussed.
[0166] FIG. 52 shows an exemplary process for screening a patient
interested in increasing his or her depth of focus. The process
begins at step 1300, in which the patient is fitted with soft
contact lenses, e.g., a soft contact lens is placed in each of the
patient's eyes. If needed, the soft contact lenses may include
vision correction. Next, at step 1310, the visual axis of each of
the patient's eyes is located as described above. At a step 1320, a
mask, such as any of those described above, is placed on the soft
contact lenses such that the optical axis of the aperture of the
mask is aligned with the visual axis of the eye. In this position,
the mask will be located generally concentric with the patient's
pupil. In addition, the curvature of the mask should parallel the
curvature of the patient's cornea. The process continues at a step
1330, in which the patient is fitted with a second set of soft
contact lenses, i.e., a second soft contact lens is placed over the
mask in each of the patient's eyes. The second contact lens holds
the mask in a substantially constant position. Last, at step 1340,
the patient's vision is tested. During testing, it is advisable to
check the positioning of the mask to ensure that the optical axis
of the aperture of the mask is substantially collinear with the
visual axis of the eye. Further details of testing are set forth in
U.S. Pat. No. 6,554,424, issued Apr. 29, 2003, incorporated by
reference herein in its entirety.
[0167] In accordance with a still further embodiment of the
invention, a mask is surgically implanted into the eye of a patient
interested in increasing his or her depth of focus. For example, a
patient may suffer from presbyopia, as discussed above. The mask
may be a mask as described herein, similar to those described in
the prior art, or a mask combining one or more of these properties.
Further, the mask may be configured to correct visual aberrations.
To aid the surgeon surgically implanting a mask into a patient's
eye, the mask may be pre-rolled or folded for ease of
implantation.
[0168] The mask may be implanted in several locations. For example,
the mask may be implanted underneath the cornea's epithelium sheet,
beneath the cornea's Bowman membrane, in the top layer of the
cornea's stroma, or in the cornea's stroma. When the mask is placed
underneath the cornea's epithelium sheet, removal of the mask
requires little more than removal of the cornea's epithelium
sheet.
[0169] FIGS. 53a through 53c show a mask 1400 inserted underneath
an epithelium sheet 1410. In this embodiment, the surgeon first
removes the epithelium sheet 1410. For example, as shown in FIG.
53a, the epithelium sheet 1410 may be rolled back. Then, as shown
in FIG. 53b, the surgeon creates a depression 1415 in a Bowman's
membrane 420 corresponding to the visual axis of the eye. The
visual axis of the eye may be located as described above and may be
marked by use of the alignment apparatus 1200 or other similar
apparatus. The depression 1415 should be of sufficient depth and
width to both expose the top layer 1430 of the stroma 1440 and to
accommodate the mask 1400. The mask 1400 is then placed in the
depression 1415. Because the depression 1415 is located in a
position to correspond to the visual axis of the patient's eye, the
central axis of the pinhole aperture of the mask 1400 will be
substantially collinear with the visual axis of the eye. This will
provide the greatest improvement in vision possible with the mask
1400. Last, the epithelium sheet 1410 is placed over the mask 1400.
Over time, as shown in FIG. 53c, the epithelium sheet 1410 will
grow and adhere to the top layer 1430 of the stroma 1440, as well
as the mask 1400 depending, of course, on the composition of the
mask 1400. As needed, a contact lens may be placed over the incised
cornea to protect the mask.
[0170] FIGS. 54a through 54c show a mask 1500 inserted beneath a
Bowman's membrane 1520 of an eye. In this embodiment, as shown in
FIG. 54a, the surgeon first hinges open the Bowman's membrane 1520.
Then, as shown in FIG. 54b, the surgeon creates a depression 1515
in a top layer 1530 of a stroma 1540 corresponding to the visual
axis of the eye. The visual axis of the eye may be located as
described above and may be marked by using the alignment apparatus
1200 or other similar apparatus. The depression 1515 should be of
sufficient depth and width to accommodate the mask 1500. Then, the
mask 1500 is placed in the depression 1515. Because the depression
1515 is located in a position to correspond to the visual axis of
the patient's eye, the central axis of the pinhole aperture of the
mask 1500 will be substantially collinear with the visual axis of
the eye. This will provide the greatest improvement in vision
possible with the mask 1500. Last, the Bowman's membrane 1520 is
placed over the mask 1500. Over time, as shown in FIG. 54c, the
epithelium sheet 1510 will grow over the incised area of the
Bowman's membrane 1520. As needed, a contact lens may be placed
over the incised cornea to protect the mask.
[0171] In another embodiment, a mask of sufficient thinness, i.e.,
less than substantially 20 microns, may be placed underneath
epithelium sheet 1410. In another embodiment, an optic mark having
a thickness less than about 20 microns may be placed beneath
Bowman's membrane 1520 without creating a depression in the top
layer of the stroma.
[0172] In an alternate method for surgically implanting a mask in
the eye of a patient, the mask may be threaded into a channel
created in the top layer of the stroma. In this method, a curved
channeling tool creates a channel in the top layer of the stroma,
the channel being in a plane parallel to the surface of the cornea.
The channel is formed in a position corresponding to the visual
axis of the eye. The channeling tool either pierces the surface of
the cornea or, in the alternative, is inserted via a small
superficial radial incision. In the alternative, a laser focusing
an ablative beam may create the channel in the top layer of the
stroma. In this embodiment, the mask may be a single segment with a
break, or it may be two or more segments. In any event, the mask in
this embodiment is positioned in the channel and is thereby located
so that the central axis of the pinhole aperture formed by the mask
is substantially collinear with the patient's visual axis to
provide the greatest improvement in the patient's depth of
focus.
[0173] In another alternate method for surgically implanting a mask
in the eye of a patient, the mask may be injected into the top
layer of the stroma. In this embodiment, an injection tool with a
stop penetrates the surface of the cornea to the specified depth.
For example, the injection tool may be a ring of needles capable of
producing a mask with a single injection. In the alternative, a
channel may first be created in the top layer of the stroma in a
position corresponding to the visual axis of the patient. Then, the
injector tool may inject the mask into the channel. In this
embodiment, the mask may be a pigment, or it may be pieces of
pigmented material suspended in a bio-compatible medium. The
pigment material may be made of a polymer or, in the alternative,
made of a suture material. In any event, the mask injected into the
channel is thereby positioned so that the central axis of the
pinhole aperture formed by the pigment material is substantially
collinear with the visual axis of the patient.
[0174] In another method for surgically implanting a mask in the
eye of a patient, the mask may be placed beneath the corneal flap
created during keratectomy, when the outermost 20% of the cornea is
hinged open. As with the implantation methods discussed above, a
mask placed beneath the corneal flap created during keratectomy
should be substantially aligned with the patient's visual axis, as
discussed above, for greatest effect.
[0175] In another method for surgically implanting a mask in the
eye of a patient, the mask may be aligned with the patient's visual
axis and placed in a pocket created in the cornea's stroma.
[0176] Further details concerning alignment apparatuses are
disclosed in U.S. Provisional Application Ser. No. 60/479,129,
filed Jun. 17, 2003, incorporated by reference herein in its
entirety.
IV. Further Surgical Systems for Aligning a Pinhole Aperture with a
Patient's Eye
[0177] FIG. 55 shows a surgical system 2000 that employs dual
target fixation in a manner similar to that discussed above in
connection with FIGS. 43-51. The surgical system 2000 enables the
identification of a unique feature of a patient's eye in connection
with a surgical procedure. The surgical system 2000 is similar to
the ophthalmic instrument 1200 except as set forth below. As
discussed below, in one arrangement, the surgical system 2000 is
configured to align an axis of the patient's eye, e.g., the
patient's line of sight (sometimes referred to herein as the
"visual axis"), with an axis of the system 2000. The axis of the
system 2000 may be a viewing axis along which the patient may
direct an eye. As discussed above, such alignment is particularly
useful in many surgical procedures, including those that benefit
from precise knowledge of the location of one or more structures or
features of the eye on which the procedures is being performed.
[0178] In one embodiment, the surgical system 2000 includes a
surgical viewing device 2004 and an alignment device 2008. In one
embodiment, the surgical viewing device 2004 includes a surgical
microscope. The surgical viewing device 2004 may be any device or
combination of devices that enables a surgeon to visualize the
surgical site with sufficient clarity or that enhances the
surgeon's visualization of the surgical site. A surgeon also may
elect to use the alignment device 2004 without a viewing device. As
discussed more fully below in connection another embodiment of a
surgical system shown in FIG. 56, the surgical system 2000
preferably also includes a fixture configured to conveniently mount
one or more components to the surgical viewing device 2004.
[0179] In one embodiment, the alignment device 2008 includes an
alignment module 2020, a marking module 2024, and an image capture
module 2028. As discussed below, in another embodiment, the marking
module 2024 is eliminated. Where the marking module 2024 is
eliminated, one or more of its functions may be performed by the
image capture module 2028. In another embodiment, the image capture
module 2028 is eliminated. The alignment device 2004 preferably
also has a control device 2032 that directs one or more components
of the alignment device 2004. As discussed more fully below, the
control device 2032 includes a computer 2036 and signal lines
2040a, 2040b, and a trigger 2042 in one embodiment.
[0180] The alignment module 2020 includes components that enable a
patient to align a feature related to the patient's eye, vision, or
sense of sight with an instrument axis, e.g., an axis of the
alignment device 2008. In one embodiment, the alignment module 2020
includes a plurality of targets (e.g., two targets) that are
located on the instrument axis. In the illustrated embodiment, the
alignment module 2020 includes a first target 2056 and a second
target 2060. The alignment module 2020 may be employed to align the
patient's line-of-sight with an axis 2052 that extends
perpendicular to the faces of the targets 2056, 2060.
[0181] Although the alignment device 2008 could be configured such
that the patient is positioned relative thereto so that the eye is
positioned along the axis 2052, it may be more convenient to
position the patient such that an eye 2064 of the patient is not on
the axis 2052. For example, as shown in FIG. 55, the patient may be
positioned a distance 2068 from the axis 2052. FIG. 55 shows that
the gaze of the patient's eye 2064 is directed generally along a
patient viewing axis 2072.
[0182] In this arrangement, the alignment device 2008 is configured
such that the patient viewing axis 2072 is at about a ninety degree
angle with respect to the instrument axis 2052. In this embodiment,
a path 2076 optically connecting the targets 2056, 2060 with the
patient's eye 2064 extends partially along the axis 2052 and
partially along the patient viewing axis 2072. The optical path
2076 defines the path along which the images of the targets 2056,
2060 are cast when the alignment device 2008 is configured such
that the patient's eye 2064 is not on the axis 2052.
[0183] Positioning the patient off of the axis 2052, may be
facilitated by one or more components that redirect light traveling
along or parallel to the axis 2052. In one embodiment, the
alignment device 2008 includes a beamsplitter 2080 located on the
axis 2052 to direct along the patient viewing axis 2072 light rays
coming toward the beamsplitter 2080 from the direction of the
targets 2056, 2060. In this embodiment, at least a portion of the
optical path 2076 is defined from the patient's eye 2064 to the
beamsplitter 2080 and from the beamsplitter 2080 to the first and
second targets 2056, 2060. Although the alignment device 2008 is
configured to enable the patient viewing axis 2072 to be at about a
ninety degree angle with respect to the axis 2052, other angles are
possible and may be employed as desired. The arrangement of FIG. 55
is convenient because it enables a surgeon to be directly above and
relatively close to the patient if the patient is positioned on his
or her back on an operating table.
[0184] In one embodiment, the first target 2056 is on the axis 2052
and on the optical path 2076 between the second target 2060 and the
patient's eye 2064. More particularly, light rays that are directed
from the second target 2060 intersect the first target 2056 and are
thereafter directed toward the beamsplitter 2080. As discussed more
fully below, the first and second targets 2056, 2060 are configured
to project a suitable pattern toward the patient's eye 2064. The
patient interacts with the projected images of the first and second
targets 2056, 2060 to align the line-of-sight (or other unique
anatomical feature) of the patient's eye 2064 or of the patient's
sense of vision with an axis of the instrument, such as the axis
2052, the viewing axis 2072, or the optical path 2076.
[0185] The first and second targets 2056, 2060 may take any
suitable form. The targets 2056, 2060 may be similar to those
hereinbefore described. The targets 2056, 2060 may be formed on
separate reticles or as part of a single alignment target. In one
embodiment, at least one of the first and second targets 2056, 2060
includes a glass reticle with a pattern formed thereon. The pattern
on the first target 2056 and the pattern on the second target 2060
may be linear patterns that are combined to form a third linear
pattern when the patient's line-of-sight is aligned with the axis
2052 or optical path 2076.
[0186] Although shown as separate elements, the first and second
targets 2056, 2060 may be formed on a alignment target. FIGS.
55A-55C shows one embodiment of an alignment target 2081. The
alignment target 2081 can be formed of glass or another
substantially transparent medium. The alignment target 2081
includes a first surface 2082 and a second surface 2083. The first
and second surfaces 2082, 2083 are separated by a distance 2084.
The distance 2084 is selected to provide sufficient separation
between the first and second surfaces 2082, 2083 to facilitate
alignment by the patient by any of the methods described herein. In
one embodiment, the alignment target 2081 includes a first pattern
2085 that may comprise a linear pattern formed on the first surface
2082 and a second pattern 2086 that may comprise a linear pattern
formed on the second surface 2083. The first and second patterns
2085, 2086 are selected so that when the patient's line-of-sight is
properly aligned with an axis of the alignment device 2008, the
first and second patterns 2085, 2086 form a selected pattern (as in
FIG. 55B) but when the patient's line-of-sight is properly aligned
with an axis of the alignment device 2008, the first and second
patterns 2085, 2086 do not form the selected pattern (as in FIG.
55C). In the illustrated embodiment, the first and second pattern
2085, 2086 each are generally L-shaped. When aligned, the first and
second patterns 2085, 2086 form a cross. When not aligned, a gap is
formed between the patterns and they appear as an L and an inverted
L. This arrangement advantageously exploits vernier acuity, which
is the ability of the eye to keenly detect misalignment of
displaced lines. Any other combination of non-linear or linear
patterns (e.g., other linear patterns that exploit vernier acuity)
can be used as targets, as discussed above.
[0187] The first and second targets 2056, 2060 (or the first and
second patterns 2085, 2086) may be made visible to the patient's
eye 2064 in any suitable manner. For example, a target illuminator
2090 may be provided to make the targets 2056, 2060 visible to the
eye 2064. In one embodiment, the target illuminator 2090 is a
source of radiant energy, such as a light source. The light source
can be any suitable light source, such as an incandescent light, a
fluorescent light, one or more light emitting diodes, or any other
source of light to illuminate the targets 2056, 2060.
[0188] As discussed more fully below, the alignment module 2020
also may include one or more optic elements, such as lenses, that
relatively sharply focus the images projected from the first and
second targets 2056, 2060 to present sharp images to the patient's
eye 2064. In such arrangements, the focal length of the optic
element or system of optical elements may be located at any
suitable location, e.g., at the first or second targets 2056, 2060,
between the first and second targets 2056, 2060 in front of the
first target 2056, or behind the second target 2060. The focal
length is the distance from a location (e.g., the location of an
optic element) to the plane at which the optic element focuses the
target images projected from the first and second target 2056,
2060.
[0189] FIG. 55 shows a series of arrows that indicate the
projection of the images of the first and second targets 2056, 2060
to the patient's eye 2064. In particular, an arrow 2094 indicates
the direction of light cast by the target illuminator 2090 along
the axis 2052 toward the first and second targets 2056, 2060. The
light strikes the first and second targets 2056, 2060 and is
absorbed by or passed through the targets to cast an image of the
targets 2056, 2060 along the axis 2052 in a direction indicated by
an arrow 2098. In the embodiment of FIG. 55, the image of the first
and second targets 2056, 2060 intersects a beamsplitter 2102 that
forms a part of the marking module 2024 and the image capture
module 2028. The beamsplitter 2102 is configured to transmit the
majority of the light conveying the images of the first and second
targets 2056, 2060 toward the beamsplitter 2080 as indicated by an
arrow 2106. The beamsplitter 2102 will be discussed in greater
detail below. The light is thereafter reflected by the beamsplitter
2080 along the patient viewing axis 2072 and toward the patient's
eye 2064. As discussed more fully below, in some embodiments, the
beamsplitter 2080 transmits some of the incident light beyond the
beamsplitter 2080 along the axis 2050. In one embodiment, 70
percent of the light incident on the beamsplitter 2080 is reflected
toward the patient's eye 2064 and 30 percent is transmitter. One
skilled in the art will recognize that the beamsplitter 2080 can be
configured to transmit and reflect in any suitable fraction.
[0190] While the target illuminator 2090 and the first and second
targets 2056, 2060 project the images of the targets to the
patient's eye 2064, the patient may interact with those images to
align a feature of the patient's eye 2064 with an axis of the
alignment device 2008. In the embodiment illustrated by FIG. 55,
the patient aligns the line-of-sight of the eye 2064 with the
patient viewing axis 2072 of the alignment device 2008.
[0191] Techniques for aligning the line of sight of the patient's
eye 2064 with the instrument axis have been discussed above. In the
context of the embodiment of FIG. 55, the patient is positioned
such that the optical path 2076 intersects the patient's eye 2064.
In one method, the patient is instructed to focus on the first
target 2056. Motion is provided between the patient's eye 2064 and
the optical path 2076 (and therefore between the patient's eye 2064
and the targets 2056, 2060). The relative motion between the
patient's eye 2064 and the targets 2056, 2060 may be provided by
the patient moving his or her head with respect to the patient
viewing axis 2072. Alternatively, the patient may be enabled to
move all or a portion of the surgical system 2000 while the patient
remains stationary. As discussed above, when the first and second
targets 2056, 2060 appear aligned (e.g., the L patterns 2085, 2086
merge to form a cross), the line-of-sight of the patient is aligned
with the patient viewing axis 2072, the optical path 2076, and the
axis 2052 of the alignment module 2020.
[0192] Although aligning the eye may be sufficient to provide
relatively precise placement of the masks described herein, one or
both of the marking module 2024 and the image capture module 2028
may be included to assist the surgeon in placing a mask after the
eye 2064 has been aligned. At least one of the marking module 2024
and the image capture module 2028 may be used to correlate the
line-of-sight of the patient's eye 2064, which is not otherwise
visible, with a visual cue, such as a visible physical feature of
the patient's eye, a marker projected onto the eye or an image of
the eye, or a virtual image of a marker visible to the surgeon, or
any combination of the foregoing. As is discussed in more detail
below, the virtual image may be an image that is directed toward
the surgeon's eye that appears from the surgeon's point of view to
be on the eye 2064 at a pre-selected location.
[0193] In one embodiment, the marking module 2024 is configured to
produce an image, sometimes referred to herein as a "marking
image", that is visible to the surgeon and that is assists the
surgeon in placing a mask or performing another surgical procedure
after the line of sight of the eye 2064 has been located. The
marking module 2024 of the alignment device 2008 shown includes a
marking target 2120 and a marking target illuminator 2124. The
marking target illuminator 2124 preferably is a source of light,
such as any of those discussed above in connection with the target
illuminator 2090.
[0194] FIG. 55 shows that in one embodiment, the marking target
2120 is a structure configured to produce a marking image when
light is projected onto the marking target 2120. The marking target
2120 may be similar to the targets 2056, 2060. In some embodiments,
the marking target 2120 is a glass reticle with a suitable
geometrical pattern formed thereon. The pattern formed on the
marking target 2120 may be a clear two dimensional shape that is
surrounded by one or more opaque regions. For example, a clear
annulus of selected width surrounded by opaque regions could be
provided. In another embodiment, the marking target 2120 may be a
glass reticle with an opaque two dimensional shape surrounded by
substantially clear regions. As discussed below, in other
embodiments, the marking target 2120 need not be made of glass and
need not have a fixed pattern. The marking target 2120 may be
located in any suitable location with respect to the beamsplitter
2080 or the alignment device 2008 as discussed below.
[0195] FIG. 55 shows that in one embodiment, the marking image is
generated in a manner similar to the manner in which the images of
the first and second targets 2056, 2060 are generated. In
particular, the marking target 2124 and the marking target
illuminator 2124 cooperate to produce, generate, or project the
marking image along a marking image axis 2128. The marking image is
conveyed by light along the axis 2128. The marking target
illuminator 2124 casts light toward the marking target 2120 in a
direction indicated by an arrow 2132. The marking target 2120
interacts with the light cast by the marking target illuminator
2124, e.g., by at least one of transmitting, absorbing, filtering,
and attenuating at least a portion of the light. An arrow 2136
indicates the direction along which the marking image generated by
the interaction of the marking target illuminator 2124 and the
marking target 2120 is conveyed. The marking image preferably is
conveyed along the marking axis 2128. In the illustrated
embodiment, the marking target 2120 is located off of the axis 2052
and the image of the marking target initially is cast in a
direction generally perpendicular to the axis 2052.
[0196] A beamsplitter 2140, to be discussed below in connection
with the image capture module 2028, is positioned on the marking
axis 2128 in the embodiment of FIG. 55. However, the beamsplitter
2140 is configured to be substantially transparent to light being
transmitted along the marking axis 2128 from the direction of the
marking target 2120. Thus, the light conveying the marking image is
substantially entirely transmitted beyond the beamsplitter 2140
along the marking axis 2128 toward the axis 2052 as indicated by an
arrow 2144. Thus, the beamsplitter 2140 generally does not affect
the marking image. A surface of the beamsplitter 2102 that faces
the marking target 2120 is reflective to light. Thus, the light
conveying the marking image is reflected and thereafter is conveyed
along the axis 2052 as indicated by the arrow 2106. The surface of
the beamsplitter 2080 that faces the beamsplitter 2102 also is
reflective to at least some light (e.g., 70 percent of the incident
light, as discussed above). Thus, the light conveying the marking
image is reflected and thereafter is conveyed along the patient
viewing axis 2072 toward the patient's eye 2064 as indicated by the
arrow 2148. Thus, a marking image projected from the marking target
2120 may be projected onto the patient's eye 2064.
[0197] As discussed more fully below, projecting the marking image
onto the patient's eye 2064 may assist the surgeon in accurately
placing a mask. For example, the surgeon may be assisted in that
the location of line-of-sight of the patient's eye (or some other
generally invisible feature of the eye 2064) is correlated with a
visible feature of the eye, such as the iris or other anatomical
feature. In one technique, the marking image is a substantially
circular ring that has a diameter that is greater than the size of
the inner periphery of the iris under surgical conditions (e.g.,
the prevailing light and the state of dilation of the patient's eye
2064). In another technique, the marking image is a substantially
circular ring that has a diameter that is less than the size of the
outer periphery of the iris under surgical conditions (e.g., light
and dilation of the eye 2064). In another technique, the marking
image is a substantially circular ring that has a size that is
correlated to another feature of the eye 2064, e.g., the limbus of
the eye.
[0198] In one embodiment of the system 2000, a marking module is
provided that includes a secondary marking module. The secondary
marking module is not routed through the optics of associated with
the alignment device 2008. Rather, the secondary marking module is
coupled with the alignment device 2008. In one embodiment, the
secondary marking module includes a source of radiant energy, e.g.,
a laser or light source similar to any of these discussed herein.
The source of radiant energy is configured to direct a plurality of
spots (e.g., two, three, four, or more than four spots) onto the
patient's eye 2064. The spots preferably are small, bright spots.
The spots indicate positions on the eye 2064 that correlate with a
feature of a mask, such as an edge of a mask, when the mask is in
the correct position with respect to the line-of-sight of the eye
2064. The spots can be aligned with the projected marking target
such that they hit at a selected location on the projected marking
target (e.g., circumferentially spaced locations on the inner edge,
on the outer edge, or on both the inner and outer edges). Thus, the
marking module may give a visual cue as to the proper positioning
of a mask that is correlated to the location of the line-of-sight
without passing through the optics of the alignment device. The
visual cue of the secondary marking module may be coordinated with
the marking image of the marking module 2024 in some
embodiments.
[0199] In some techniques, it may be beneficial to increase the
visibility of a visual cue generated for the benefit of the surgeon
(e.g., the reflection of the image of the marking target 2120) on
the eye 2064. In some cases, this is due to the generally poor
reflection of marking images off of the cornea. Where reflection of
the marking image off of the cornea is poor, the reflection of the
image may be quite dim. In addition, the cornea is an off-center
aspherical structure, so the corneal reflection (purkinje images)
may be offset from the location of the intersection of the visual
axis and the corneal surface as viewed by the surgeon.
[0200] One technique for increasing the visibility of a visual cue
involves applying a substance to the eye that can react with the
projected image of the marking target 2120. For example, a dye,
such as fluorescein dye, can be applied to the surface of the eye.
Then the marking target illuminator 2124 may be activated to cause
an image of the marking target 2120 to be projected onto the eye,
as discussed above. In one embodiment, the marking target
illuminator 2124 is configured to project light from all or a
discrete portion of the visible spectrum of electromagnetic radiant
energy, e.g., the wavelengths corresponding to blue light, to
project the image of the marking target 2120 onto the eye 2064. The
projected image interacts with the dye and causes the image of the
marking target 2120 to be illuminated on the surface of the cornea.
The presence of the dye greatly increases the visibility of the
image of the marking target. For example, where the marking target
2120 is a ring, a bright ring will be visible to the surgeon
because the light causes the dye to fluoresce. This technique
substantially eliminates errors in placement of a mask due to the
presence of the purkinje images and may generally increase the
brightness of the image of the marking target 2120.
[0201] Another technique for increasing the visibility of a visual
cue on the eye involves applying a visual cue enhancing device to
at least a portion of the anterior surface of the eye 2064. For
example, in one technique, a drape is placed over the cornea. The
drape may have any suitable configuration. For example, the drape
may be a relatively thin structure that will substantially conform
to the anterior structure of the eye. The drape may be formed in a
manner similar to the formation of a conventional contact lens. In
one technique, the drape is a contact lens. The visual cue
enhancing device preferably has suitable reflecting properties. In
one embodiment, the visual cue enhancing device diffusely reflects
the light projecting the image of the marking target 2120 onto the
cornea. In one embodiment, the visual cue enhancing device is
configured to interact with a discrete portion of the visible
spectrum of electromagnetic radiant energy, e.g., the wavelengths
thereof corresponding to blue light.
[0202] As discussed above the alignment device 2008 shown in FIG.
55 also includes an image capture module 2028. Some variations do
not include the image capture module 2028. The image capture module
2028 of the surgical system 2000 is capable of capturing one or
more images of the patient's eye 2064 to assist the surgeon in
performing surgical procedures on the eye 2064. The image capture
module 2028 preferably includes a device to capture an image, such
as a camera 2200 and a display device 2204 to display an image. The
display device 2204 may be a liquid crystal display. The image
capture module 2028 may be controlled in part by the control device
2032 of the surgical system 2000. For example, the computer 2036
may be employed to process images captured by the camera 2200 and
to convey an image to the display device 2204 where it is made
visible to the surgeon. The computer 2036 may also direct the
operation of or be responsive to at least one of the camera 2200,
the display device 2204, the trigger 2042, and any other component
of the image capture module 2028.
[0203] The camera 2200 can be any suitable camera. One type of
camera that can be used is a charge-coupled device camera, referred
to herein as a CCD camera. One type of CCD camera incorporates a
silicon chip, the surface of which includes light-sensitive pixels.
When light, e.g., a photon or light particle, hits a pixel, an
electric charge is registered at the pixels that can be detected.
Images of sufficient resolution can be generated with a large array
of sensitive pixels. As discussed more fully below, one
advantageous embodiment provides precise alignment of a selected
pixel (e.g., one in the exact geometric center of the display
device 2204) with the axis 2052. When such alignment is provided,
the marking module may not be needed to align a mask with the
line-of-sight of the eye 2064.
[0204] As discussed above, an image captured by the camera 2200
aids the surgeon attempting to align a mask, such as any of the
masks described herein, with the eye 2064. In one arrangement, the
image capture module 2028 is configured to capture an image of one
or more physical attributes of the eye 2064, the location of which
may be adequately correlated to the line-of-sight of the eye 2064.
For example, the image of the patient's iris may be directed along
the patient viewing axis 2072 to the beamsplitter 2080 as indicated
by the arrow 2148. As mentioned above, a side of the beamsplitter
2080 that faces the beamsplitter 2080 is reflective to light
transmitted from the eye 2064. Thus, at least a substantial portion
of the light conveying the image of the iris of the eye 2064 is
reflected by the beamsplitter 2080 and is conveyed along the axis
2052 toward the beamsplitter 2102, as indicated by the arrow 2106.
As discussed above, the surface of the beamsplitter 2102 facing the
beamsplitter 2080 is reflective to light. Thus, substantially all
of the light conveying the image of the iris is reflected by the
beamsplitter 2102 and is conveyed along the marking axis 2128
toward the beamsplitter 2140, as indicated by the arrow 2144. The
surface of the beamsplitter 2140 facing the beamsplitter 2102 and
the camera 2200 is reflective to light. Thus, substantially all of
the light conveying the image of the iris is reflected along an
image capture axis 2212 that extends between the beamsplitter 2140
and the camera 2200. The light is conveyed along an image capture
axis 2212 as indicated by an arrow 2216.
[0205] The image captured by the camera 2200 is conveyed to the
computer 2036 by way of a signal line 2040a. The computer 2036
processes the signal in a suitable manner and generates signals to
be conveyed along a signal line 2040b to the display device 2204.
Any suitable signal line and computer or other signal processing
device can be used to convey signals from the camera 2200 to the
display device 2204. The signal lines 2040a, 2040b need not be
physical lines. For example, any suitable wireless technology may
be used in combination with or in place of physical lines or
wires.
[0206] The capturing of the image by the camera 2200 may be
triggered in any suitable way. For example, the trigger 2042 may be
configured to be manually actuated. In one embodiment, the trigger
2042 is configured to be actuated by the patient when his or her
eye 2064 is aligned (e.g., when the targets 2056, 2060 are aligned,
as discussed above). By enabling the patient to trigger the
capturing of the image of the eye 2064 by the image capture module
2028, the likelihood of the eye 2064 moving prior to the capturing
of the image is greatly reduced. In another embodiment, another
person participating in the procedure may be permitted to trigger
the capturing of the image, e.g., on the patient's cue. In another
embodiment, the control device 2032 may be configured to
automatically capture the image of the patient's eye 2064 based on
a predetermined criteria.
[0207] The display device 2204 is configured to be illuminated to
direct an image along the axis 2052 toward the beamsplitter 2080 as
indicated by an arrow 2208. The surface of the beamsplitter 2080
that faces the display device 2204 preferably is reflective to
light directed from the location of the beamsplitter 2080. Thus,
the image on the display 2052 is reflected by the beamsplitter 2080
toward an eye 2212 of the surgeon as indicated by an arrow 2216.
The beamsplitter 2080 preferably is transparent from the
perspective of the surgeon's eye 2212. Thus, the surgeon may
simultaneously view the patient's eye 2064 and the image on the
display device 2204 in one embodiment. In one embodiment where both
the marking module 2024 and the image capture module 2028 are
present, the marking image may be projected at the same time that
an image is displayed on the display device 2204. The marking image
and the image on the display will appear to both be on the
patient's eye. In one arrangement, they have the same configuration
(e.g., size and shape) and therefore overlap. This can reinforce
the image from the perspective of the surgeon, further increasing
the visibility of the visual cue provided by the marking image.
[0208] The display device 2204 is located at a distance 2220 from
the beamsplitter 2080. The patient is located a distance 2224 from
the axis 2052. Preferably the distance 2220 is about equal to the
distance 2224. Thus, both the display device 2204 and the patient's
eye 2064 are at the focal length of the surgical viewing device
2004. This assures that the image generated by the display device
2204 is in focus at the same time that the patient's eye is in
focus.
[0209] In one embodiment, the system 2000 is configured to track
movement of the patient's eye 2064 during the procedure. In one
configuration, the trigger 2042 is actuated by the patient when the
eye 2064 is aligned with an axis of the alignment device 2008.
Although a mask is implanted shortly thereafter, the patient's eye
is not constrained and may thereafter move to some extent. In order
to correct for such movement, the image capture module 2028 may be
configured to respond to such movements by moving the image formed
on the display device 2204. For example, a ring may be formed on
the display device 2204 that is similar to those discussed above in
connection with the marking target 2120. The beamsplitter 2080
enables the surgeon to see the ring visually overlaid on the
patient's eye 2064. The image capture module 2028 compares the
real-time position of the patient's eye 2064 with the image of the
eye captured when the trigger 2042 is actuated. Differences in the
real-time position and the position captured by the camera 2200 are
determined. The position of the ring is moved an amount
corresponding to the differences in position. As a result, from the
perspective of the surgeon, movements of the ring and the eye
correspond and the ring continues to indicate the correct position
to place a mask.
[0210] As discussed above, several variations of the system 2000
are contemplated. A first variation is substantially identical to
the embodiment shown in FIG. 55, except as set forth below. In the
first variation, the video capture module 2028 is eliminated. This
embodiment is similar to that set forth above in connection with
FIG. 51. In the arrangement of FIG. 55, the marking module 2024 is
configured to project the marking target onto the surface of the
patient's eye. This variation is advantageous in that it has a
relatively simple construction. Also, this variation projects the
marking image onto the surface of the cornea, proximate the
surgical location.
[0211] In one implementation of the first variation, the marking
module 2024 is configured to display the marking image to the
surgeon's eye 2212 but not to the patient's eye 2064. This may be
provided by positioning the marking target 2120 approximately in
the location of the display device 2204. The marking image may be
generated and presented to the surgeon in any suitable manner. For
example, the marking target 2120 and marking target illuminator
2124 may be repositioned so that they project the image of the
marking target 2120 as indicated by the arrows 2208, 2216. The
marking target 2120 and the marking target illuminator 2124 may be
replaced by a unitary display, such as an LCD display. This
implementation of the first variation is advantageous in that the
marking image is visible to the surgeon but is not visible to the
patient. The patient is freed from having to respond to or being
subject to the marking image. This can increase alignment
performance by increasing patient comfort and decreasing
distractions, thereby enabling the patient to remain still during
the procedure.
[0212] In another implementation of the first variation, a dual
marking image is presented to the eye 2212 of the surgeon. In one
form, this implementation has a marking module 2024 similar to that
shown in FIG. 55 and discussed above, except as set forth below. A
virtual image is presented to the surgeon's eye 2212. In one form,
a virtual image generation surface is positioned in substantially
the same location as the display device 2204. The surface may be a
mirror, another reflective surface, or a non-reflective surface. In
one embodiment, the display device 2204 is a white card. A first
fraction of the light conveying the marking image is reflected by
the beamsplitter 2080 to the patient's eye 2064. The marking image
is thus formed on the patient's eye. A second fraction of the light
conveying the marking image is transmitted to the virtual image
generation surface. The marking image is formed on or reflected by
the virtual image generation surface. The marking target thus also
is visible to the surgeon's eye 2212 in the form of a virtual image
of the target. The virtual image and the marking image formed on
the patient's eye are both visible to the surgeon. This
implementation of the first variation is advantageous in that the
virtual image and the marking image of the marking target are
visible to the surgeon's eye 2212 and are reinforced each other
making the marking image highly visible to the surgeon.
[0213] In a second variation, the marking module 2024 is
eliminated. In this embodiment, the image capture module 2028
provides a visual cue for the surgeon to assist in the placement of
a mask. In particular, an image can be displayed on the display
device 2204, as discussed above. The image can be generated in
response to the patient actuating the trigger 2042. In one
technique, the patient actuates the trigger when the targets 2056,
2060 appear aligned, as discussed above. In this variation, care
should be taken to determine the position of the display device
2204 in the alignment device because the image formed on the
display device 2204 is to give the surgeon a visual cue indicating
the location of the line-of-sight of the patient. In one
embodiment, the display device 2204 is carefully coupled with the
alignment module so that the axis 2052 extends through a known
portion (e.g., a known pixel) thereof. Because the precise location
of the axis 2052 on the display device 2204 is known, the
relationship of the image formed thereon to the line-of-sight of
the patient is known.
[0214] FIG. 56 shows a portion of a surgical system 2400 that is
similar to the surgical system 2000 discussed above except as set
forth below. The surgical system 2400 may be modified according to
any of the variations and embodiments hereinbefore described.
[0215] The portion of the surgical system 2400 is shown from the
surgeon's viewpoint in FIG. 56. The surgical system 2400 includes
an alignment device 2404 and a fixture 2408. The alignment device
2404 is similar to the alignment device 2008 discussed above,
except as set forth below. The surgical system 2400 is shown
without a surgical microscope or other viewing device, but is
configured to be coupled with one by way of the fixture 2408.
[0216] The fixture 2408 may take any suitable form. In the
illustrated embodiment, the fixture 2408 includes a clamp 2412, an
elevation adjustment mechanism 2416, and suitable members to
interconnect the clamp 2408 and the mechanism 2416. In the
embodiment of FIG. 56, the clamp 2412 is a ring clamp that includes
a first side portion 2420, a second side portion 2424, and a
clamping mechanism 2426 to actuate the first and second side
portion 2420, 2424 with respect to each other. The first side
portion 2420 has a first arcuate inner surface 2428 and the second
side portion 2424 has a second arcuate inner surface 2432 that
faces the first arcuate inner surface 2428. The clamping mechanism
2426 is coupled with each of the first and second side portions
2420, 2424 to cause the first and second arcuate inner surfaces
2428, 2432 to move toward or away from each other. As the first and
second arcuate inner surfaces 2428, 2432 move toward each other
they apply a force to a structure, such as a portion of a surgical
microscope, placed between the first and second arcuate inner
surfaces 2428, 2432. In one embodiment, the force applied by the
first and second arcuate inner surfaces 2428, 2432 is sufficient to
clamp the alignment device 2404 with respect to a surgical viewing
aid. In one embodiment, the clamp 2412 is configured to couple with
any one of (or more than one of) the currently commercially
available surgical microscopes.
[0217] The fixture 2408 preferably also is configured to suspend
the alignment device 2404 at an elevation below the clamp 2412. In
the illustrated embodiment, a bracket 2440 is coupled with the
clamp 2412, which is an L-shaped bracket in the illustrated
embodiment with a portion of the L extending downward from the
clamp 2412. FIG. 56 shows the L-shaped bracket spaced laterally
from the clamp 2412 by a spacer 2444. In one embodiment, the
bracket 2440 is pivotably coupled with the spacer 2444 so that the
alignment device 2404 can be easily rotated out of the field of
view of the surgical microscope or viewing aid, which is visible
through the spaced defined between the surfaces 2428, 2432.
[0218] Preferably the fixture 2408 is also configured to enable the
alignment device 2404 to be positioned at a selected elevation
within a range of elevations beneath the clamp 2412. The elevation
of the alignment device 2404 may be easily and quickly adjusted by
manipulating a suitable mechanism. For example, manual actuation
may be employed by providing a knob 2460 coupled with a
rack-and-pinion gear coupling 2464. Of course the rack-and-pinion
gear coupling 2464 can be actuated by another manual device that is
more remote, such as by a foot pedal or trigger or by an automated
device.
[0219] FIGS. 57-59 show further details of the alignment device
2404. The alignment device 2404 is operatively coupled with an
illuminator control device 2500 and includes an alignment module
2504, a marking module 2508, and an image routing module 2512. As
discussed below, the illuminator control device 2500 controls light
or energy sources associated with the alignment control device
2404. In some embodiments, the illuminator control device 2500
forms a part of a computer or other signal processing device,
similar to the computer 2036 discussed above.
[0220] The alignment module 2504 is similar to the alignment module
2020 except as set forth below. The alignment module 2504 includes
a housing 2520 that extends between a first end 2524 and a second
end 2528. The first end 2524 of the housing 2520 is coupled with
the image routing module 2512 and interacts with the image routing
module 2512 in a manner described below. The housing 2520 includes
a rigid body 2532 that preferably is hollow. An axis 2536 extends
within the hollow portion of the housing 2520 between the first and
second ends 2524, 2528. In the illustrated embodiment, the second
end 2528 of the housing 2520 is enclosed by an end plate 2540.
[0221] The housing 2520 is configured to protect a variety of
components that are positioned in the hollow spaced defined
therein. In one embodiment, a target illuminator 2560 is positioned
inside the housing 2520 near the second end 2528 thereof. A power
cable 2564 (or other electrical conveyance) that extends from the
end plate 2540 electrically connects the target illuminator 2560 to
a power source. The target illuminator 2560 could also be triggered
and powered by a wireless connection. In one arrangement, the power
source forms a portion of the illuminator control device 2500 to
which the power cable 2564 is connected. Power may be from any
suitable power source, e.g., from a battery or electrical outlet of
suitable voltage.
[0222] As discussed above, the illuminator control device 2500
enables the surgeon (or other person assisting in a procedure) to
control the amount of energy supplied to the target illuminator
2560 in the alignment module 2504. In one embodiment, the
illuminator control device 2500 has a brightness control so that
the brightness of the target illumination 2560 can be adjusted. The
brightness control may be actuated in a suitable manner, such as by
a brightness control knob 2568. The brightness control may take any
other suitable form to provide manual analog (e.g., continuous)
adjustment of the amount of energy applied to the target
illuminator 2560 or to provide manual digital (e.g., discrete)
adjustment of the amount of energy applied to the target
illuminator 2560. In some embodiments, the brightness control may
be adjustable automatically, e.g., under computer control. The
illuminator control device 2500 may also have an on-off switch 2572
configured to selectively apply and cut off power to the target
illuminator 2560. The on-off switch 2572 may be operated manually,
automatically, or in a partially manual and partially automatic
mode. The brightness control and on-off switch could be controlled
wirelessly in another embodiment.
[0223] Also located in the housing 2520 are a first target 2592, a
second target 2596, and a lens 2600. As discussed above, the first
and second targets 2592, 2596 are configured to present a composite
image to the patient's eye such that the patient may align the
line-of-sight of the eye with an axis (e.g., the axis 2536) of the
alignment module 2504. The first and second targets 2592, 2596 are
similar to the targets discussed above. In particular, the
alignment target 2081, which includes two targets on opposite ends
of a single component, may be positioned within the housing
2520.
[0224] The lens 2600 may be any suitable lens. Preferably the lens
2600 is configured to sharply focus one or both of the images of
the first and second targets 2592, 2596 in a manner similar to the
focus of the targets 2056, 2060, discussed above.
[0225] In one embodiment, the alignment module 2504 is configured
such that the position of the first and second targets 2592, 2596
within the housing 2520 can be adjusted. The adjustability of the
first and second targets 2592, 2596 may be provided with any
suitable arrangement. FIGS. 57-58 shows that in one embodiment the
alignment module 2504 includes a target adjustment device 2612 to
provide rapid gross adjustment and fine adjustment of the positions
of the targets 2592, 2596 within the housing 2520.
[0226] In one embodiment, the target adjustment device 2612
includes a support member 2616 that extends along at least a
portion of the housing 2520 between the first end 2524 and the
second end 2528. In one embodiment, the support member 2616 is
coupled with the end plate 2540 and with the image routing module
2512. In one embodiment, the target adjustment device 2612 includes
a lens fixture 2620 that is coupled with the lens 2600 and a target
fixture 2624 that is coupled with the first and second targets
2592, 2596. In another embodiment, each of the first and second
targets 2592, 2596 is coupled with a separate target fixture so
that the targets may be individually positioned and adjusted. The
lens 2600 may be adjustable as shown, or in a fixed position.
Movement of the lens and the targets 2592, 2596 enable the patterns
on the targets 2592, 2596 to be brought into focus from the
patient's point of view.
[0227] In one arrangement, the support member 2616 is a threaded
rod and each of the first and second target fixtures 2620, 2624 has
a corresponding threaded through hole to receive the threaded
support member 2616. Preferably an adjustment device, such as a
knob 2628 is coupled with the threaded support member 2616 so that
the support member 2616 may be rotated. The knob 2628 may be
knurled to make it easier to grasp and rotate. Rotation of the
support member 2616 causes the first and second target fixtures
2620, 2624 to translate on the support member 2616 along the
outside of the housing 2520. The movement of the first and second
target fixtures 2620, 2624 provides a corresponding movement of the
first and second targets 2592, 2596 within the housing 2520.
[0228] In one embodiment a quick release mechanism 2640 is provided
to enable the first and second target fixtures 2620, 2624
selectively to clamp and to release the support member 2616. The
quick release mechanism 2640 can be a spring loaded clamp that
causes the through holes formed in the first and second target
fixtures 2620, 2624 to open to create a gap through which the
support member 2616 can pass. When the first and second target
fixtures 2620, 2624 are removed from the support member 2616, the
can be quickly moved to another position on the support member
2616. After rapid repositioning, fine positioning of the first and
second target fixtures 2620, 2624 may be achieved with by turning
the support member 2616.
[0229] As discussed above, the alignment device 2404 also includes
a marking module 2508 that is similar to the marking module 2024
described above, except as set forth below. The marking module
includes a housing 2642 that is generally rigid and that defines a
hollow space within the housing. The housing 2642 includes a first
end 2644 that is coupled with the image routing module 2512 and a
second end 2648 that is closed by an end plate 2652. In one
embodiment, the housing 2642 includes a first portion 2656 and a
second portion 2660. The first and second portions 2656, 2660
preferably are configured to be disengaged from each other so that
components located in the hollow space defined in the housing 2642
to be accessed. Such rapid access facilitates servicing and
reconfiguring of the components located in the housing 2642. The
first portion 2656 extends between the first end 2644 and a
midpoint of the housing 2642. The second portion 2660 extends
between the first portion 2656 and the second end 2648 of the
housing 2642. In one embodiment, the first portion 2656 has a male
member with external threads and the second portion 2660 has a
female member with internal thread such that the first and second
portions 2656, 2660 may be engaged with and disengaged from each
other by way of the threads.
[0230] As discussed above, the housing 2642 provides a space in
which one or more components may be positioned. In the illustrated
embodiment, the housing 2642 encloses a marking target illuminator
2680 and a marking target 2684.
[0231] The marking target illuminator 2680 may be a suitable source
of radiant energy, e.g., a light source, such as an incandescent
light, a fluorescent light, a light-emitting diode, or other source
of radiant energy. As with the target illuminators discussed above,
the marking target illuminator 2680 may include or be coupled with
suitable optical components to process the light generated thereby
in a useful manner, e.g., by providing one or more filters to
modify the light, e.g., by allowing a subset of the spectrum of
light energy emitted by the light source (e.g., one or more bands
of the electromagnetic spectrum) to be transmitted toward the
marking target 2684.
[0232] In the illustrated embodiment, the marking target
illuminator 2680 is located near the end plate 2652. A power cable
2688 (or other electrical conveyance) that extends from the end
plate 2652 electrically connects the marking target illuminator
2680 to a power source. In one arrangement, the power source forms
a portion of the illuminator control device 2500 to which the power
cable 2688 is connected. Power may be from any suitable power
source, e.g., from a battery or electrical outlet of suitable
voltage.
[0233] As discussed above, the illuminator control device 2500
enables the surgeon (or other person assisting in a procedure) to
control the amount of energy supplied to the target illuminator
2680 in the marking module 2508. The illuminator control device
2500 has a brightness control so that the brightness of the marking
target illumination 2680 can be adjusted. The brightness control
may be actuated in a suitable manner, such as by a brightness
control knob 2692. The brightness control may be similar to that
discussed above in connection with the brightness control of the
target illuminator 2560. The illuminator control device 2500 may
also have an on-off switch 2696 configured to selectively apply and
cut off power to the marking target illuminator 2680. The on-off
switch 2696 may be operated manually, automatically, or in a
partially manual and partially automatic mode. Any of the power
supply, the brightness control, and the on-off switch may be
implemented wirelessly in various other embodiments.
[0234] In one embodiment, the marking target 2684 is a reticle,
e.g., made of glass, with an annular shape formed thereon. For
example, the annular shape formed on the marking target 2684 may be
a substantially clear annulus surrounded by opaque regions. In this
configuration, light directed toward the marking target 2684
interacts with the marking target 2684 to produce and annular
image. In another embodiment, the marking target 2684 may be a
substantially clear reticle with an opaque shape, such as an opaque
annular shape. The annular image is directed into the image routing
device 2684, as discussed further below. The marking target 2684
may be housed in a fixture 2718 that is removable, e.g., when the
first portion 2656 and the second portion 2660 of the housing 2642
are decoupled. The first portion 2656 of the housing 2642 is
configured to engage the fixture 2718 to relatively precisely
position the marking target 2684 with respect to an axis of the
housing 2642.
[0235] FIG. 59 shows the image routing module 2512 in greater
detail. The image routing module 2512 is primarily useful for
routing light that conveys the target and marking images to an eye
of a patient. The image routing module 2512 provides flexibility in
the positioning of the various components of the alignment device
2404. For example, the image routing module 2512 enables the
housing 2520 and the housing 2556 to be generally in the same plane
and positioned generally parallel to each other. This provides a
relatively compact arrangement for the alignment device 2404, which
is advantageous in the surgical setting because, as discussed
above, it is desirable for the surgeon to be as close to the
surgical site as possible. In addition, the compact arrangement of
the alignment device 2404 minimizes or at least reduces the extent
to which the alignment device 2404 interferes with free movement of
the surgeon and others assisting the surgeon.
[0236] FIGS. 58 and 59 shows that the image routing module 2512
includes a housing 2720 that is coupled with the first end 2524 and
the housing 2520 and with the first end 2644 of the housing 2642. A
space defined within the housing 2720 houses a first optic device
2728 and a second optic device 2732. The first optic device 2728
has a reflective surface that faces the marking target 2684 and is
configured to reflect light conveying an image of the marking
target 2684 toward the second optic device 2732. The first optic
device 2728 may be a mirror. The second optic device 2732 has a
surface 2736 that faces the first optic device 2728 and is
reflective to light from the first optic device 2728. The second
optic device 2732 thus reflects light that is directed toward it by
the first optic device 2728.
[0237] The image routing module 2512 also may include a third optic
device 2740 and a frame 2744 coupled with the housing 2720. The
frame 2744 is configured to position and orient the third optic
device 2740 with respect to the housing 2720. In one embodiment,
the third optic device 2740 is a beamsplitter and the frame 2744
holds the third optic device 2740 at about a forty-five degree
angle with respect to the axis 2520. In this position, the third
optic device 2740 interacts with light reflected by the first
surface 2736 of the second optic device 2732. The third optic
device 2740 may operate in a manner similar to the beamsplitter
2080 of FIG. 55.
[0238] The second optic device 2732 is configured to be transparent
to substantially all of the light conveying an image along the axis
2536 such that the image conveyed along the axis 2536 may be
directed to the third optic device 2740 and thereafter to an eye of
a surgeon, as discussed about in connection with FIG. 55.
[0239] Although the image routing device is shown with first,
second, and third optic devices 2728, 2732, 2740 to route light
conveying images in a particular manner, one skilled in the art
will recognize that the image routing device 2512 could have more
or fewer optic devices that route the image, depending on the
desired geometry and compactness of the alignment device 2404.
[0240] A variation of the alignment device 2404 provides a marking
module with a secondary marking module not routed through the
optics of the alignment device 2404. In one embodiment, the
secondary marking module includes a source of radiant energy, e.g.,
a laser or other light source. The source of radiant energy is
configured to direct a plurality of spots (e.g., three, four, or
more than four spots) onto the patient's eye. The spots indicate
positions on the eye that correlate with an edge of a mask when the
mask is in the correct position with respect to the line-of-sight
of the eye 2064. The spots can be aligned with the projected
marking target such that they hit at a selected location on the
projected marking target (e.g., circumferentially spaced locations
on the inner edge, on the outer edge, or on both the inner and
outer edges). At least a portion of the secondary marking module is
coupled with the frame 2744 in one embodiment. A laser of the
secondary marking module could be attached to the frame 2744 and
suspended therefrom, oriented downward toward the patient's eye. As
discussed above, this arrangement provides a secondary device for
marking the proper location of a mask with respect to a patient's
line of sight after the line of sight has been identified.
[0241] Although various exemplary embodiments of apparatuses and
methods for aligning a patient's line-of-sight with an axis of an
instrument in connection with the application of a mask have been
discussed hereinabove, it should be apparent to those skilled in
the art that various changes and modifications can be made which
will achieve at least some of the advantages of the invention
without departing from, the true scope of the invention. These and
other obvious modifications are intended to be covered by the
appended claims.
V. Masks Configured to Reduce the Visibility of Diffraction
Patterns
[0242] Many of the foregoing masks can be used to improve the depth
of focus of a patient. Various additional mask embodiments are
discussed below. Some of the embodiments described below include
nutrient transport structures that are configured to enhance or
maintain nutrient flow between adjacent tissues by facilitating
transport of nutrients across the mask. The nutrient transport
structures of some of the embodiments described below are
configured to at least substantially prevent nutrient depletion in
adjacent tissues. The nutrient transport structures can decrease
negative effects due to the presence of the mask in adjacent
corneal layers when the mask is implanted in the cornea, increasing
the longevity of the masks. The inventors have discovered that
certain arrangements of nutrient transport structures generate
diffraction patterns that interfere with the vision improving
effect of the masks described herein. Accordingly, certain masks
are described herein that include nutrient transport structures
that do not generate diffraction patterns or otherwise interfere
with the vision enhancing effects of the mask embodiments.
[0243] FIGS. 60-61 show one embodiment of a mask 3000 configured to
increase depth of focus of an eye of a patient suffering from
presbyopia. The mask 3000 is similar to the masks hereinbefore
described, except as set forth below. Also, the mask 3000 can be
formed by any suitable process, such as those discussed below in
connection with FIGS. 67a-67d with variations of such processes.
The mask 3000 is configured to be applied to an eye of a patient,
e.g., by being implanted in the cornea of the patient. The mask
3000 may be implanted within the cornea in any suitable manner,
such as those discussed above in connection with FIGS. 53A-54C.
[0244] In one embodiment, the mask 3000 includes a body 3004 that
has an anterior surface 3008 and a posterior surface 3012. In one
embodiment, the body 3004 is capable of substantially maintaining
natural nutrient flow between the first corneal layer and the
second corneal layer. In one embodiment, the material is selected
to maintain at least about ninety-six percent of the natural flow
of at least one nutrient (e.g., glucose) between a first corneal
layer (e.g., the layer 1410) and a second corneal layer (e.g., the
layer 1430). The body 3004 may be formed of any suitable material,
including at least one of an open cell foam material, an expanded
solid material, and a substantially opaque material. In one
embodiment, the material used to form the body 3004 has relatively
high water content.
[0245] In one embodiment, the mask 3000 includes and a nutrient
transport structure 3016. The nutrient transport structure 3016 may
comprise a plurality of holes 3020. The holes 3020 are shown on
only a portion of the mask 3000, but the holes 3020 preferably are
located throughout the body 3004 in one embodiment. In one
embodiment, the holes 3020 are arranged in a hex pattern, which is
illustrated by a plurality of locations 3020' in FIG. 62A. As
discussed below, a plurality of locations may be defined and later
used in the later formation of a plurality of holes 3020 on the
mask 3000. The mask 3000 has an outer periphery 3024 that defines
an outer edge of the body 3004. In some embodiments, the mask 3000
includes an aperture 3028 at least partially surrounded by the
outer periphery 3024 and a non-transmissive portion 3032 located
between the outer periphery 3024 and the aperture 3028.
[0246] Preferably the mask 3000 is symmetrical, e.g., symmetrical
about a mask axis 3036. In one embodiment, the outer periphery 3024
of the mask 3000 is circular. The masks in general have has a
diameter within the range of from about 3 mm to about 8 mm, often
within the range of from about 3.5 mm to about 6 mm, and less than
about 6 mm in one embodiment. In another embodiment, the mask is
circular and has a diameter in the range of 4 to 6 mm. In another
embodiment, the mask 3000 is circular and has a diameter of less
than 4 mm. The outer periphery 3024 has a diameter of about 3.8 mm
in another embodiment. In some embodiments, masks that are
asymmetrical or that are not symmetrical about a mask axis provide
benefits, such as enabling a mask to be located or maintained in a
selected position with respect to the anatomy of the eye.
[0247] The body 3004 of the mask 3000 may be configured to coupled
with a particular anatomical region of the eye. The body 3004 of
the mask 3000 may be configured to conform to the native anatomy of
the region of the eye in which it is to be applied. For example,
where the mask 3000 is to be coupled with an ocular structure that
has curvature, the body 3004 may be provided with an amount of
curvature along the mask axis 3036 that corresponds to the
anatomical curvature. For example, one environment in which the
mask 3000 may be deployed is within the cornea of the eye of a
patient. The cornea has an amount of curvature that varies from
person to person about a substantially constant mean value within
an identifiable group, e.g., adults. When applying the mask 3000
within the cornea, at least one of the anterior and posterior
surfaces 3008, 3012 of the mask 3000 may be provided with an amount
of curvature corresponding to that of the layers of the cornea
between which the mask 3000 is applied.
[0248] In some embodiments, the mask 3000 has a desired amount of
optical power. Optical power may be provided by configuring the at
least one of the anterior and posterior surfaces 3008, 3012 with
curvature. In one embodiment, the anterior and posterior surfaces
3008, 3012 are provided with different amounts of curvature. In
this embodiment, the mask 3000 has varying thickness from the outer
periphery 3024 to the aperture 3028.
[0249] In one embodiment, one of the anterior surface 3008 and the
posterior surface 3012 of the body 3004 is substantially planar. In
one planar embodiment, very little or no uniform curvature can be
measured across the planar surface. In another embodiment, both of
the anterior and posterior surfaces 3008, 3012 are substantially
planar. In general, the thickness of the inlay may be within the
range of from about 1 micron to about 40 micron, and often in the
range of from about 5 micron to about 20 micron. In one embodiment,
the body 3004 of the mask 3000 has a thickness 3038 of between
about 5 micron and about 10 micron. In one embodiment, the
thickness 3038 of the mask 3000 is about 5 micron. In another
embodiment, the thickness 3038 of the mask 3000 is about 8 micron.
In another embodiment, the thickness 3038 of the mask 3000 is about
10 micron.
[0250] Thinner masks generally are more suitable for applications
wherein the mask 3000 is implanted at a relatively shallow location
in (e.g., close to the anterior surface of) the cornea. In thinner
masks, the body 3004 may be sufficiently flexible such that it can
take on the curvature of the structures with which it is coupled
without negatively affecting the optical performance of the mask
3000. In one application, the mask 3000 is configured to be
implanted about 5 um beneath the anterior surface of the cornea. In
another application, the mask 3000 is configured to be implanted
about 65 um beneath the anterior surface of the cornea. In another
application, the mask 3000 is configured to be implanted about 125
um beneath the anterior surface of the cornea. Further details
regarding implanting the mask 3000 in the cornea are discussed
above in connection with FIGS. 53A-54C.
[0251] A substantially planar mask has several advantages over a
non-planar mask. For example, a substantially planar mask can be
fabricated more easily than one that has to be formed to a
particular curvature. In particular, the process steps involved in
inducing curvature in the mask 3000 can be eliminated. Also, a
substantially planar mask may be more amenable to use on a wider
distribution of the patient population (or among different
sub-groups of a broader patient population) because the
substantially planar mask uses the curvature of each patient's
cornea to induce the appropriate amount of curvature in the body
3004.
[0252] In some embodiments, the mask 3000 is configured
specifically for the manner and location of coupling with the eye.
In particular, the mask 3000 may be larger if applied over the eye
as a contact lens or may be smaller if applied within the eye
posterior of the cornea, e.g., proximate a surface of the lens of
the eye. As discussed above, the thickness 3038 of the body 3004 of
the mask 3000 may be varied based on where the mask 3000 is
implanted. For implantation at deeper levels within the cornea, a
thicker mask may be advantageous. Thicker masks are advantageous in
some applications. For example, they are generally easier to
handle, and therefore are easier to fabricate and to implant.
Thicker masks may benefit more from having a preformed curvature
than thinner masks. A thicker mask could be configured to have
little or no curvature prior to implantation if it is configured to
conform to the curvature of the native anatomy when applied.
[0253] The aperture 3028 is configured to transmit substantially
all incident light along the mask axis 3036. The non-transmissive
portion 3032 surrounds at least a portion of the aperture 3028 and
substantially prevents transmission of incident light thereon. As
discussed in connection with the above masks, the aperture 3028 may
be a through-hole in the body 3004 or a substantially light
transmissive (e.g., transparent) portion thereof. The aperture 3028
of the mask 3000 generally is defined within the outer periphery
3024 of the mask 3000. The aperture 3028 may take any of suitable
configurations, such as those described above in connection with
FIGS. 6-42.
[0254] In one embodiment, the aperture 3028 is substantially
circular and is substantially centered in the mask 3000. The size
of the aperture 3028 may be any size that is effective to increase
the depth of focus of an eye of a patient suffering from
presbyopia. For example, the aperture 3028 can be circular, having
a diameter of less than about 2.2 mm in one embodiment. In another
embodiment, the diameter of the aperture is between about 1.8 mm
and about 2.2 mm. In another embodiment, the aperture 3028 is
circular and has a diameter of about 1.8 mm or less. Most apertures
will have a diameter within the range of from about 1.0 mm to about
2.5 mm, and often within the range of from about 1.3 mm to about
1.9 mm.
[0255] The non-transmissive portion 3032 is configured to prevent
transmission of radiant energy through the mask 3000. For example,
in one embodiment, the non-transmissive portion 3032 prevents
transmission of substantially all of at least a portion of the
spectrum of the incident radiant energy. In one embodiment, the
non-transmissive portion 3032 is configured to prevent transmission
of substantially all visible light, e.g., radiant energy in the
electromagnetic spectrum that is visible to the human eye. The
non-transmissive portion 3032 may substantially prevent
transmission of radiant energy outside the range visible to humans
in some embodiments.
[0256] As discussed above in connection with FIG. 3, preventing
transmission of light through the non-transmissive portion 3032
decreases the amount of light that reaches the retina and the fovea
that would not converge at the retina and fovea to form a sharp
image. As discussed above in connection with FIG. 4, the size of
the aperture 3028 is such that the light transmitted therethrough
generally converges at the retina or fovea. Accordingly, a much
sharper image is presented to the eye than would otherwise be the
case without the mask 3000.
[0257] In one embodiment, the non-transmissive portion 3032
prevents transmission of about 90 percent of incident light. In
another embodiment, the non-transmissive portion 3032 prevents
transmission of about 92 percent of all incident light. The
non-transmissive portion 3032 of the mask 3000 may be configured to
be opaque to prevent the transmission of light. As used herein the
term "opaque" is intended to be a broad term meaning capable of
preventing the transmission of radiant energy, e.g., light energy,
and also covers structures and arrangements that absorb or
otherwise block all or less than all or at least a substantial
portion of the light. In one embodiment, at least a portion of the
body 3004 is configured to be opaque to more than 99 percent of the
light incident thereon.
[0258] As discussed above, the non-transmissive portion 3032 may be
configured to prevent transmission of light without absorbing the
incident light. For example, the mask 3000 could be made reflective
or could be made to interact with the light in a more complex
manner, as discussed in U.S. Pat. No. 6,554,424, issued Apr. 29,
2003, which is hereby incorporated by reference herein in its
entirety;
[0259] As discussed above, the mask 3000 also has a nutrient
transport structure that in some embodiments comprises the
plurality of holes 3020. The presence of the plurality of holes
3020 (or other transport structure) may affect the transmission of
light through the non-transmissive portion 3032 by potentially
allowing more light to pass through the mask 3000. In one
embodiment, the non-transmissive portion 3032 is configured to
absorb about 99 percent or more of the incident light from passing
through the mask 3000 without holes 3020 being present. The
presence of the plurality of holes 3020 allows more light to pass
through the non-transmissive portion 3032 such that only about 92
percent of the light incident on the non-transmissive portion 3032
is prevented from passing through the non-transmissive portion
3032. The holes 3020 may reduce the benefit of the aperture 3028 on
the depth of focus of the eye by allowing more light to pass
through the non-transmissive portion to the retina.
[0260] Reduction in the depth of focus benefit of the aperture 3028
due to the holes 3020 is balanced by the nutrient transmission
benefits of the holes 3020. In one embodiment, the transport
structure 3016 (e.g., the holes 3020) is capable of substantially
maintaining natural nutrient flow from a first corneal layer (i.e.,
one that is adjacent to the anterior surface 3008 of the mask 3000)
to the second corneal layer (i.e., one that is adjacent to the
posterior surface 3012 of the mask 3000). The plurality of holes
3020 are configured to enable nutrients to pass through the mask
3000 between the anterior surface 3008 and the posterior surface
3012. As discussed above, the holes 3020 of the mask 3000 shown in
FIG. 60 may be located anywhere on the mask 3000. Other mask
embodiments described herein below locate substantially all of the
nutrient transport structure in one or more regions of a mask.
[0261] The holes 3020 of FIG. 60 extends at least partially between
the anterior surface 3008 and the posterior surface 3012 of the
mask 3000. In one embodiment, each of the holes 3020 includes a
hole entrance 3060 and a hole exit 3064. The hole entrance 3060 is
located adjacent to the anterior surface 3008 of the mask 3000. The
hole exit 3064 is located adjacent to the posterior surface 3012 of
the mask 3000. In one embodiment, each of the holes 3020 extends
the entire distance between the anterior surface 3008 and the
posterior surface 3012 of the mask 3000.
[0262] The transport structure 3016 is configured to maintain the
transport of one or more nutrients across the mask 3000. The
transport structure 3016 of the mask 3000 provides sufficient flow
of one or more nutrients across the mask 3000 to prevent depletion
of nutrients at least at one of the first and second corneal layers
(e.g., the layers 1410 and 1430). One nutrient of particular
importance to the viability of the adjacent corneal layers is
glucose. The transport structure 3016 of the mask 3000 provides
sufficient flow of glucose across the mask 3000 between the first
and second corneal layers to prevent glucose depletion that would
harm the adjacent corneal tissue. Thus, the mask 3000 is capable of
substantially maintaining nutrient flow (e.g., glucose flow)
between adjacent corneal layers. In one embodiment, the nutrient
transport structure 3016 is configured to prevent depletion of more
than about 4 percent of glucose (or other biological substance) in
adjacent tissue of at least one of the first corneal layer and the
second corneal layer.
[0263] The holes 3020 may be configured to maintain the transport
of nutrients across the mask 3000. In one embodiment, the holes
3020 are formed with a diameter of about 0.015 mm or more. In
another embodiment, the holes have a diameter of about 0.020 mm. In
another embodiment, the holes have a diameter of about 0.025 mm. In
another embodiment, the holes 3020 have a diameter in the range of
about 0.020 mm to about 0.029 mm. The number of holes in the
plurality of holes 3020 is selected such that the sum of the
surface areas of the hole entrances 3060 of all the holes 3000
comprises about 5 percent or more of surface area of the anterior
surface 3008 of the mask 3000. In another embodiment, the number of
holes 3020 is selected such that the sum of the surface areas of
the hole exits 3064 of all the holes 3020 comprises about 5 percent
or more of surface area of the posterior surface 3012 of the mask
3000. In another embodiment, the number of holes 3020 is selected
such that the sum of the surface areas of the hole exits 3064 of
all the holes 3020 comprises about 5 percent or more of surface
area of the posterior surface 3012 of the mask 3012 and the sum of
the surface areas of the hole entrances 3060 of all the holes 3020
comprises about 5 percent or more of surface area of the anterior
surface 3008 of the mask 3000.
[0264] Each of the holes 3020 may have a relatively constant
cross-sectional area. In one embodiment, the cross-sectional shape
of each of the holes 3020 is substantially circular. Each of the
holes 3020 may comprise a cylinder extending between the anterior
surface 3008 and the posterior surface 3012.
[0265] The relative position of the holes 3020 is of interest in
some embodiments. As discussed above, the holes 3020 of the mask
3000 are hex-packed, e.g., arranged in a hex pattern. In
particular, in this embodiment, each of the holes 3020 is separated
from the adjacent holes 3020 by a substantially constant distance,
sometimes referred to herein as a hole pitch 3072. In one
embodiment, the hole pitch 3072 is about 0.062 mm.
[0266] In a hex pattern, the angles between lines of symmetry are
approximately 60 degrees. The spacing of holes along any line of
holes is generally within the range of from about 30 microns to
about 100 microns, and, in one embodiment, is approximately 60
microns. The hole diameter is generally within the range of from
about 10 microns to about 100 microns, and in one embodiment, is
approximately 20 microns. The hole spacing and diameter are related
if you want to control the amount of light coming through. The
light transmission is a function of the sum of hole areas as will
be understood by those of skill in the art in view of the
disclosure herein.
[0267] The embodiment of FIG. 60 advantageously enables nutrients
to flow from the first corneal layer to the second corneal layer.
The inventors have discovered that negative visual effects can
arise due to the presence of the transport structure 3016. For
example, in some cases, a hex packed arrangement of the holes 3020
can generate diffraction patterns visible to the patient. For
example, patients might observe a plurality of spots, e.g., six
spots, surrounding a central light with holes 3020 having a hex
patterned.
[0268] The inventors have discovered a variety of techniques that
produce advantageous arrangements of a transport structure such
that diffraction patterns and other deleterious visual effects do
not substantially inhibit other visual benefits of a mask. In one
embodiment, where diffraction effects would be observable, the
nutrient transport structure is arranged to spread the diffracted
light out uniformly across the image to eliminate observable spots.
In another embodiment, the nutrient transport structure employs a
pattern that substantially eliminates diffraction patterns or
pushes the patterns to the periphery of the image.
[0269] FIG. 62B-62C show two embodiments of patterns of holes 4020
that may be applied to a mask that is otherwise substantially
similar to the mask 3000. The holes 4020 of the hole patterns of
FIGS. 62A-62B are spaced from each other by a random hole spacing
or hole pitch. In other embodiments discussed below, holes are
spaced from each other by a non-uniform amount, e.g., not a random
amount. In one embodiment, the holes 4020 have a substantially
uniform shape (cylindrical shafts having a substantially constant
cross-sectional area). FIG. 62C illustrates a plurality of holes
4020 separated by a random spacing, wherein the density of the
holes is greater than that of FIG. 62B. Generally, the higher the
percentage of the mask body that has holes the more the mask will
transport nutrients in a manner similar to the native tissue. One
way to provide a higher percentage of hole area is to increase the
density of the holes. Increase hole density can also permit smaller
holes to achieve the same nutrient transport as is achieved by less
dense, larger holes.
[0270] FIG. 63A shows a portion of another mask 4000a that is
substantially similar to the mask 3000, except as set forth below.
The mask 4000a can be formed by any suitable process, such as those
discussed below in connection with FIGS. 67a-67d and with
variations of such processes. The mask 4000a has a plurality of
holes 4020a. A substantial number of the holes 4020a have a
non-uniform size. The holes 4020a may be uniform in cross-sectional
shape. The cross-sectional shape of the holes 4020a is
substantially circular in one embodiment. The holes 4020a may be
circular in shape and have the same diameter from a hole entrance
to a hole exit, but are otherwise non-uniform in at least one
aspect, e.g., in size. It may be preferable to vary the size of a
substantial number of the holes by a random amount. In another
embodiment, the holes 4020a are non-uniform (e.g., random) in size
and are separated by a non-uniform (e.g., a random) spacing.
[0271] FIG. 63B illustrates another embodiment of a mask 4000b that
is substantially similar to the mask 3000, except as set forth
below. Also, the mask 4000b can be formed by any suitable process,
such as those discussed below in connection with FIGS. 67a-67d and
with variations of such processes. The mask 4000b includes a body
4004b. The mask 4000b has a transport structure 4016b that includes
a plurality of holes 4020b with a non-uniform facet orientation. In
particular, each of the holes 4020b has a hole entrance that may be
located at an anterior surface 4008b of the mask 4000b. A facet of
the hole entrance is defined by a portion of the body 4004b of the
mask 4000b surrounding the hole entrance. The facet is the shape of
the hole entrance at the anterior surface 4008b. In one embodiment,
most or all the facets have an elongate shape, e.g., an oblong
shape, with a long axis and a short axis that is perpendicular to
the long axis. The facets may be substantially uniform in shape. In
one embodiment, the orientation of facets is not uniform. For
example, a substantial number of the facets may have a non-uniform
orientation. In one arrangement, a substantial number of the facets
have a random orientation. In some embodiments, the facets are
non-uniform (e.g., random) in shape and are non-uniform (e.g.,
random) in orientation.
[0272] Other embodiments may be provided that vary at least one
aspect, including one or more of the foregoing aspects, of a
plurality of holes to reduce the tendency of the holes to produce
visible diffraction patterns or patterns that otherwise reduce the
vision improvement that may be provided by a mask with an aperture,
such as any of those described above. For example, in one
embodiment, the hole size, shape, and orientation of at least a
substantial number of the holes may be varied randomly or may be
otherwise non-uniform.
[0273] FIG. 64 shows another embodiment of a mask 4200 that is
substantially similar to any of the masks hereinbefore described,
except as set forth below. Also, the mask 4200 can be formed by any
suitable process, such as those discussed below in connection with
FIGS. 67a-67d and with variations of such processes. The mask 4200
includes a body 4204. The body 4204 has an outer peripheral region
4205, an inner peripheral region 4206, and a hole region 4207. The
hole region 4207 is located between the outer peripheral region
4205 and the outer peripheral region 4206. The body 4204 may also
include an aperture region, where the aperture (discussed below) is
not a through hole. The mask 4200 also includes a nutrient
transport structure 4216. In one embodiment, the nutrient transport
structure includes a plurality of holes 4220. At least a
substantial portion of the holes 4220 (e.g., all of the holes) are
located in the hole region 4207. As above, only a portion of the
nutrient structure 4216 is shown for simplicity. But it should be
understood that the hole 4220 may be located through the hole
region 4207.
[0274] The outer peripheral region 4205 may extend from an outer
periphery 4224 of the mask 4200 to a selected outer circumference
4225 of the mask 4200. The selected outer circumference 4225 of the
mask 4200 is located a selected radial distance from the outer
periphery 4224 of the mask 4200. In one embodiment, the selected
outer circumference 4225 of the mask 4200 is located about 0.05 mm
from the outer periphery 4224 of the mask 4200.
[0275] The inner peripheral region 4206 may extend from an inner
location, e.g., an inner periphery 4226 adjacent an aperture 4228
of the mask 4200 to a selected inner circumference 4227 of the mask
4200. The selected inner circumference 4227 of the mask 4200 is
located a selected radial distance from the inner periphery 4226 of
the mask 4200. In one embodiment, the selected inner circumference
4227 of the mask 4200 is located about 0.05 mm from the inner
periphery 4226.
[0276] The mask 4200 may be the product of a process that involves
random selection of a plurality of locations and formation of holes
on the mask 4200 corresponding to the locations. As discussed
further below, the method can also involve determining whether the
selected locations satisfy one or more criteria. For example, one
criterion prohibits all, at least a majority, or at least a
substantial portion of the holes from being formed at locations
that correspond to the inner or outer peripheral regions 4205,
4206. Another criterion prohibits all, at least a majority, or at
least a substantial portion of the holes 4220 from being formed too
close to each other. For example, such a criterion could be used to
assure that a wall thickness, e.g., the shortest distance between
adjacent holes, is not less than a predetermined amount. In one
embodiment, the wall thickness is prevented from being less than
about 20 microns.
[0277] In a variation of the embodiment of FIG. 64, the outer
peripheral region 4205 is eliminated and the hole region 4207
extends from the inner peripheral region 4206 to an outer periphery
4224. In another variation of the embodiment of FIG. 64, the inner
peripheral region 4206 is eliminated and the hole region 4207
extends from the outer peripheral region 4205 to an inner periphery
4226.
[0278] FIG. 61B shows a mask 4300 that is similar to the mask 3000
except as set forth below. The mask 4300 can be formed by any
suitable process, such as those discussed below in connection with
FIGS. 67a-67d and with variations of such processes. The mask 4300
includes a body 4304 that has an anterior surface 4308 and a
posterior surface 4312. The mask 4300 also includes a nutrient
transport structure 4316 that, in one embodiment, includes a
plurality of holes 4320. The holes 4320 are formed in the body 4304
so that nutrient transport is provided but transmission of radiant
energy (e.g., light) to the retinal locations adjacent the fovea
through the holes 4304 is substantially prevented. In particular,
the holes 4304 are formed such that when the eye with which the
mask 4300 is coupled is directed at an object to be viewed, light
conveying the image of that object that enters the holes 4320
cannot exit the holes along a path ending near the fovea.
[0279] In one embodiment, each of the holes 4320 has a hole
entrance 4360 and a hole exit 4364. Each of the holes 4320 extends
along a transport axis 4366. The transport axis 4366 is formed to
substantially prevent propagation of light from the anterior
surface 4308 to the posterior surface 4312 through the holes 4320.
In one embodiment, at least a substantial number of the holes 4320
have a size to the transport axis 4366 that is less than a
thickness of the mask 4300. In another embodiment, at least a
substantial number of the holes 4320 have a longest dimension of a
perimeter at least at one of the anterior or posterior surfaces
4308, 4312 (e.g., a facet) that is less than a thickness of the
mask 4300. In some embodiments, the transport axis 4366 is formed
at an angle with respect to a mask axis 4336 that substantially
prevents propagation of light from the anterior surface 4308 to the
posterior surface 4312 through the hole 4320. In another
embodiment, the transport axis 4366 of one or more holes 4320 is
formed at an angle with respect to the mask axis 4336 that is large
enough to prevent the projection of most of the hole entrance 4360
from overlapping the hole exit 4364.
[0280] In one embodiment, the hole 4320 is circular in
cross-section and has a diameter between about 0.5 micron and about
8 micron and the transport axis 4366 is between 5 and 85 degrees.
The length of each of the holes 4320 (e.g., the distance between
the anterior surface 4308 and the posterior surface 4312) is
between about 8 and about 92 micron. In another embodiment, the
diameter of the holes 4320 is about 5 micron and the transport
angle is about 40 degrees or more. As the length of the holes 4320
increases it may be desirable to include additional holes 4320. In
some cases, additional holes 4320 counteract the tendency of longer
holes to reduce the amount of nutrient flow through the mask
4300.
[0281] FIG. 61C shows another embodiment of a mask 4400 similar to
the mask 3000, except as set forth below. The mask 4400 can be
formed by any suitable process, such as those discussed below in
connection with FIGS. 67a-67d and with variations of such
processes. The mask 4400 includes a body 4404 that has an anterior
surface 4408, a first mask layer 4410 adjacent the anterior surface
4408, a posterior surface 4412, a second mask layer 4414 adjacent
the posterior surface 4412, and a third mask layer 4415 located
between the first mask layer 4410 and the second mask layer 4414.
The mask 4400 also includes a nutrient transport structure 4416
that, in one embodiment, includes a plurality of holes 4420. The
holes 4420 are formed in the body 4404 so that nutrient are
transported across the mask, as discussed above, but transmission
of radiant energy (e.g., light) to retinal locations adjacent the
fovea through the holes 4404 is substantially prevented. In
particular, the holes 4404 are formed such that when the eye with
which the mask 4400 is coupled is directed at an object to be
viewed, light conveying the image of that object that enters the
holes 4420 cannot exit the holes along a path ending near the
fovea.
[0282] In one embodiment, at least one of the holes 4420 extends
along a non-linear path that substantially prevents propagation of
light from the anterior surface to the posterior surface through
the at least one hole. In one embodiment, the mask 4400 includes a
first hole portion 4420a that extends along a first transport axis
4466a, the second mask layer 4414 includes a second hole portion
4420b extending along a second transport axis 4466b, and the third
mask layer 4415 includes a third hole portion 4420c extending along
a third transport axis 4466c. The first, second, and third
transport axes 4466a, 4466b, 4466c preferably are not collinear. In
one embodiment, the first and second transport axes 4466a, 4466b
are parallel but are off-set by a first selected amount. In one
embodiment, the second and third transport axes 4466b, 4466c are
parallel but are off-set by a second selected amount. In the
illustrated embodiment, each of the transport axes 44466a, 4466b,
4466c are off-set by one-half of the width of the hole portions
4420a, 4420b, 4420c. Thus, the inner-most edge of the hole portion
4420a is spaced from the axis 4336 by a distance that is equal to
or greater than the distance of the outer-most edge of the hole
portion 4420b from the axis 4336. This spacing substantially
prevents light from passing through the holes 4420 from the
anterior surface 4408 to the posterior surface 4412.
[0283] In one embodiment, the first and second amounts are selected
to substantially prevent the transmission of light therethrough.
The first and second amounts of off-set may be achieved in any
suitable fashion. One technique for forming the hole portions
4420a, 4420b, 4420c with the desired off-set is to provide a
layered structure. As discussed above, the mask 4400 may include
the first layer 4410, the second layer 4414, and the third layer
4415. FIG. 61C shows that the mask 4400 can be formed with three
layers. In another embodiment, the mask 4400 is formed of more than
three layers. Providing more layers may advantageously further
decrease the tendency of light to be transmitted through the holes
4420 onto the retina. This has the benefit of reducing the
likelihood that a patient will observe or otherwise perceive a
patter that will detract from the vision benefits of the mask 4400.
A further benefit is that less light will pass through the mask
4400, thereby enhancing the depth of focus increase due to the
pin-hole sized aperture formed therein.
[0284] In any of the foregoing mask embodiments, the body of the
mask may be formed of a material selected to provide adequate
nutrient transport and to substantially prevent negative optic
effects, such as diffraction, as discussed above. In various
embodiments, the masks are formed of an open cell foam material. In
another embodiment, the masks are formed of an expanded solid
material.
[0285] As discussed above in connection with FIGS. 62B and 62C,
various random patterns of holes may advantageously be provided for
nutrient transport. In some embodiment, it may be sufficient to
provide regular patterns that are non-uniform in some aspect.
Non-uniform aspects to the holes may be provided by any suitable
technique.
[0286] In a first step of one technique, a plurality of locations
4020' is generated. The locations 4020' are a series of coordinates
that may comprise a non-uniform pattern or a regular pattern. The
locations 4020' may be randomly generated or may be related by a
mathematical relationship (e.g., separated by a fixed spacing or by
an amount that can be mathematically defined). In one embodiment,
the locations are selected to be separated by a constant pitch or
spacing and may be hex packed.
[0287] In a second step, a subset of the locations among the
plurality of locations 4020' is modified to maintain a performance
characteristic of the mask. The performance characteristic may be
any performance characteristic of the mask. For example, the
performance characteristic may relate to the structural integrity
of the mask. Where the plurality of locations 4020' is selected at
random, the process of modifying the subset of locations may make
the resulting pattern of holes in the mask a "pseudo-random"
pattern.
[0288] Where a hex packed pattern of locations (such as the
locations 3020' of FIG. 62A) is selected in, the first step, the
subset of locations may be moved with respect to their initial
positions as selected in the first step. In one embodiment, each of
the locations in the subset of locations is moved by an amount
equal to a fraction of the hole spacing. For example, each of the
locations in the subset of locations may be moved by an amount
equal to one-quarter of the hole spacing. Where the subset of
locations is moved by a constant amount, the locations that are
moved preferably are randomly or pseudo-randomly selected. In
another embodiment, the subset of location is moved by a random or
a pseudo-random amount.
[0289] In one technique, an outer peripheral region is defined that
extends between the outer periphery of the mask and a selected
radial distance of about 0.05 mm from the outer periphery. In
another embodiment, an inner peripheral region is defined that
extends between an aperture of the mask and a selected radial
distance of about 0.05 mm from the aperture. In another embodiment,
an outer peripheral region is defined that extends between the
outer periphery of the mask and a selected radial distance and an
inner peripheral region is defined that extends between the
aperture of the mask and a selected radial distance from the
aperture. In one technique, the subset of location is modified by
excluding those locations that would correspond to holes formed in
the inner peripheral region or the outer peripheral region. By
excluding locations in at least one of the outer peripheral region
and the inner peripheral region, the strength of the mask in these
regions is increased. Several benefits are provided by stronger
inner and outer peripheral regions. For example, the mask may be
easier to handle during manufacturing or when being applied to a
patient without causing damage to the mask.
[0290] In another embodiment, the subset of locations is modified
by comparing the separation of the holes with minimum and or
maximum limits. For example, it may be desirable to assure that no
two locations are closer than a minimum value. In some embodiments
this is important to assure that the wall thickness, which
corresponds to the separation between adjacent holes, is no less
than a minimum amount. As discussed above, the minimum value of
separation is about 20 microns in one embodiment, thereby providing
a wall thickness of no less than about 20 microns.
[0291] In another embodiment, the subset of locations is modified
and/or the pattern of location is augmented to maintain an optical
characteristic of the mask. For example, the optical characteristic
may be opacity and the subset of locations may be modified to
maintain the opacity of a non-transmissive portion of a mask. In
another embodiment, the subset of locations may be modified by
equalizing the density of holes in a first region of the body
compared with the density of holes in a second region of the body.
For example, the locations corresponding to the first and second
regions of the non-transmissive portion of the mask may be
identified. In one embodiment, the first region and the second
region are arcuate regions (e.g., wedges) of substantially equal
area. A first areal density of locations (e.g., locations per
square inch) is calculated for the locations corresponding to the
first region and a second areal density of locations is calculated
for the locations corresponding to the second region. In one
embodiment, at least one location is added to either the first or
the second region based on the comparison of the first and second
areal densities. In another embodiment, at least one location is
removed based on the comparison of the first and second areal
densities.
[0292] The subset of locations may be modified to maintain nutrient
transport of the mask. In one embodiment, the subset of location is
modified to maintain glucose transport.
[0293] In a third step, a hole is formed in a body of a mask at
locations corresponding to the pattern of locations as modified,
augmented, or modified and augmented. The holes are configured to
substantially maintain natural nutrient flow from the first layer
to the second layer without producing visible diffraction
patterns.
VI. Further Methods of Treating a Patient
[0294] As discussed above in, various techniques are particularly
suited for treating a patient by applying masks such as those
disclosed herein to an eye. For example, in some embodiments, the
surgical system 2000 of FIG. 55 employs a marking module 2024 that
provides a visual cue in the form of a projected image for a
surgeon during a procedure for applying a mask. In addition, some
techniques for treating a patient involve positioning an implant
with the aid of a marked reference point. These methods are
illustrated by FIGS. 65-66B.
[0295] In one method, a patient is treated by placing an implant
5000 in a cornea 5004. A corneal flap 5008 is lifted to expose a
surface in the cornea 5004 (e.g., an intracorneal surface). Any
suitable tool or technique may be used to lift the corneal flap
5008 to expose a surface in the cornea 5004. For example, a blade
(e.g., a microkeratome), a laser or an electrosurgical tool could
be used to form a corneal flap. A reference point 5012 on the
cornea 5004 is identified. The reference point 5012 thereafter is
marked in one technique, as discussed further below. The implant
5000 is positioned on the intracorneal surface. In one embodiment,
the flap 5008 is then closed to cover at least a portion of the
implant 5000.
[0296] The surface of the cornea that is exposed is a stromal
surface in one technique. The stromal surface may be on the corneal
flap 5008 or on an exposed surface from which the corneal flap 5008
is removed.
[0297] The reference point 5012 may be identified in any suitable
manner. For example, the alignment devices and methods described
above may be used to identify the reference point 5012. In one
technique, identifying the reference point 5012 involves
illuminating a light spot (e.g., a spot of light formed by all or a
discrete portion of radiant energy corresponding to visible light,
e.g., red light). As discussed above, the identifying of a
reference point may further include placing liquid (e.g., a
fluorescein dye or other dye) on the intracorneal surface.
Preferably, identifying the reference point 5012 involves alignment
using any of the techniques described herein.
[0298] As discussed above, various techniques may be used to mark
an identified reference point. In one technique the reference point
is marked by applying a dye to the cornea or otherwise spreading a
material with known reflective properties onto the cornea. As
discussed above, the dye may be a substance that interacts with
radiant energy to increase the visibility of a marking target or
other visual cue. The reference point may be marked by a dye with
any suitable tool. The tool is configured so that it bites into a
corneal layer, e.g., an anterior layer of the epithelium, and
delivers a thin ink line into the corneal layer in one embodiment.
The tool may be made sharp to bite into the epithelium. In one
application, the tool is configured to deliver the dye as discussed
above upon being lightly pressed against the eye. This arrangement
is advantageous in that it does not form a larger impression in the
eye. In another technique, the reference point may be marked by
making an impression (e.g., a physical depression) on a surface of
the cornea with or without additional delivery of a dye. In another
technique, the reference point may be marked by illuminating a
light or other source of radiant energy, e.g., a marking target
illuminator and projecting that light onto the cornea (e.g., by
projecting a marking target).
[0299] Any of the foregoing techniques for marking a reference
point may be combined with techniques that make a mark that
indicates the location of an axis of the eye, e.g., the visual axis
or line-of-sight of the eye. In one technique, a mark indicates the
approximate intersection of the visual axis and a surface of the
cornea. In another technique, a mark is made approximately radially
symmetrically disposed about the intersection of the visual axis
and a surface of the cornea.
[0300] As discussed above, some techniques involve making a mark on
an intracorneal surface. The mark may be made by any suitable
technique. In one technique a mark is made by pressing an implement
against the intracorneal surface. The implement may form a
depression that has a size and shape that facilitate placement of a
mask. For example, in one form the implement is configured to form
a circular ring (e.g., a thin line of dye, or a physical
depression, or both) with a diameter that is slightly larger than
the outer diameter of a mask to be implanted. The circular ring can
be formed to have a diameter between about 4 mm and about 5 mm. The
intracorneal surface is on the corneal flap 5008 in one technique.
In another technique, the intracorneal surface is on an exposed
surface of the cornea from which the flap was removed. This exposed
surface is sometimes referred to as a tissue bed.
[0301] In another technique, the corneal flap 5008 is lifted and
thereafter is laid on an adjacent surface 5016 of the cornea 5004.
In another technique, the corneal flap 5008 is laid on a removable
support 5020, such as a sponge. In one technique, the removable
support has a surface 5024 that is configured to maintain the
native curvature of the corneal flap 5008.
[0302] FIG. 65 shows that the marked reference point 5012 is
helpful in positioning an implant on an intracorneal surface. In
particular, the marked reference point 5012 enables the implant to
be positioned with respect to the visual axis of the eye. In the
illustrated embodiment, the implant 5000 is positioned so that a
centerline of the implant, indicated as M.sub.CL, extends through
the marked reference point 5012.
[0303] FIG. 65A illustrates another technique wherein a reference
5012' is a ring or other two dimensional mark. In such a case, the
implant 5000 may be placed so that an outer edge of the implant and
the ring correspond, e.g., such that the ring and the implant 5000
share the same or substantially the same center. Preferably, the
ring and the implant 5000 are aligned so that the centerline of the
implant M.sub.CL is on the line of sight of the eye, as discussed
above. The ring is shown in dashed lines because in the illustrated
technique, it is formed on the anterior surface of the corneal flap
5008.
[0304] In one technique, the corneal flap 5008 is closed by
returning the corneal flap 5008 to the cornea 5004 with the implant
5000 on the corneal flap 5008. In another technique, the corneal
flap 5008 is closed by returning the corneal flap 5008 to the
cornea 5004 over the implant 5000, which previously was placed on
the tissue bed (the exposed intracorneal surface).
[0305] When the intracorneal surface is a stromal surface, the
implant 5000 is placed on the stromal surface. At least a portion
of the implant 5000 is covered. In some techniques, the implant
5000 is covered by returning a flap with the implant 5000 thereon
to the cornea 5004 to cover the stromal surface. In one technique,
the stromal surface is exposed by lifting an epithelial layer to
expose stroma. In another technique, the stromal surface is exposed
by removing an epithelial layer to expose stroma. In some
techniques, an additional step of replacing the epithelial layer to
at least partially cover the implant 5000 is performed.
[0306] After the flap 5008 is closed to cover at least a portion of
the implant 5000, the implant 5000 may be repositioned to some
extent in some applications. In one technique, pressure is applied
to the implant 5000 to move the implant into alignment with the
reference point 5012. The pressure may be applied to the anterior
surface of the cornea 5004 proximate an edge of the implant 5000
(e.g., directly above, above and outside a projection of the outer
periphery of the implant 5000, or above and inside a projection of
the outer periphery of the implant 5000). This may cause the
implant to move slightly away from the edge proximate which
pressure is applied. In another technique, pressure is applied
directly to the implant. The implant 5000 may be repositioned in
this manner if the reference point 5012 was marked on the flap 5008
or if the reference point 5012 was marked on the tissue bed.
Preferably, pushing is accomplished by inserting a thin tool under
the flap or into the pocket and directly moving the inlay.
[0307] FIG. 66 shows that a patient may also be treated by a method
that positions an implant 5100 in a cornea 5104, e.g., in a corneal
pocket 5108. Any suitable tool or technique may be used to create
or form the corneal pocket 5108. For example, a blade (e.g., a
microkeratome), a laser, or an electrosurgical tool could be used
to create or form a pocket in the cornea 5104. A reference point
5112 is identified on the cornea 5104. The reference point may be
identified by any suitable technique, such as those discussed
herein. The reference point 5112 is marked by any suitable
technique, such as those discussed herein. The corneal pocket 5108
is created to expose an intracorneal surface 5116. The corneal
pocket 5108 may be created at any suitable depth, for example at a
depth within a range of from about 50 microns to about 300 microns
from the anterior surface of the cornea 5104. The implant 5100 is
positioned on the intracorneal surface 5116. The marked reference
point 5112 is helpful in positioning the implant 5100 on the
intracorneal surface 5116. The marked reference point 5112 enables
the implant 5100 to be positioned with respect to the visual axis
of the eye, as discussed above. In the illustrated embodiment, the
implant 5100 is positioned so that a centerline M.sub.CL of the
implant 5100 extends through or adjacent to the marked reference
point 5112.
[0308] FIG. 66A illustrates another technique wherein a reference
5112' is a ring or other two dimensional mark. In such case, the
implant 5100 may be placed so that an outer edge of the implant and
the ring correspond, e.g., such that the ring and the implant 5100
share the same or substantially the same center. Preferably, the
ring and the implant 5100 are aligned so that the centerline of the
implant M.sub.CL is on the line of sight of the eye, as discussed
above. The ring is shown in solid lines because in the illustrated
embodiment, it is formed on the anterior surface of the cornea 5104
above the pocket 5108.
[0309] After the implant 5100 is positioned in the pocket 5108, the
implant 5100 may be repositioned to some extent in some
applications. In one technique, pressure is applied to the implant
5100 to move the implant into alignment with the reference point
5112. The pressure may be applied to the anterior surface of the
cornea 5104 proximate an edge of the implant 5100 (e.g., directly
above, above and outside a projection of the outer periphery of the
implant 5100, or above and inside a projection of the outer
periphery of the implant 5100). This may cause the implant 5100 to
move slightly away from the edge at which pressure is applied. In
another technique, pressure is applied directly to the implant
5100.
VII. Methods of Making an Ocular Implant
[0310] A variety of techniques can be used to make masks that have
desirable performance characteristics and that can correct
presbyopia and other vision defects in patients. As discussed
above, it is desirable that the mask be at least partially opaque
to visible light and UV stable in some embodiments. Also, the masks
should be sufficiently biocompatible that the mask can reside
adjacent or within eye tissue without harming the tissue. The masks
also should be relatively thin so that they are capable of being
implanted in a thin ocular structure, such as the cornea. It may
also be desirable for the masks generally to blend in with adjacent
ocular tissue so that the presence of the masks in the eye is not
visible to others. For example, the masks can be configured with a
non-reflective surface. In many embodiments, the masks are
corrosion-resistant. In some embodiments, the masks are flexible
and resilient, as it may be desirable for masks that are compressed
during deployment to expand to an uncompressed configuration
subsequent to deployment.
[0311] Additionally, applicants have discovered that these
processes and methods can be combined with other methods and
structures described herein to make a mask or implant that performs
well. For example, the methods described below can be combined with
techniques discussed above, such as techniques for forming nutrient
transport structures. In one method the mask that is formed is a
thin, micro-perforated, corneal implant that is bio-compatible and
corrosion resistant in the human eye. In one technique, the mask
has approximately 1000-3000 micro-perforations extending between a
first, e.g., convex, surface and a second, e.g., concave, surface
of the mask. The micro-perforations can have a transverse dimension
of on average between about 10 microns and about 25 microns.
[0312] The physical dimensions of the mask can vary depending on
the clinical application and individual patient. The mask is of a
shape analogous to a washer, e.g., an annulus defined between an
inner periphery and an outer periphery. The mask can have an inner
diameter of about 1.5 mm, an outer diameter of about 4 mm, and
conform to a portion of the surface of a sphere having a radius of
curvature of about 8 mm. The curvature of the mask can vary, but it
is generally selected to conform to the curvature of an anatomical
feature, e.g., the cornea of an adult human eye. The radius of
curvature of the mask can be within a range of from about 7.8 mm to
about 8.2 mm in some embodiments. The radius of curvature of the
mask can be within a range of from about 7.6 mm to about 8.4 mm in
other embodiments. The radius of curvature of the mask can be
within a range of from about 7.4 mm to about 8.6 mm in other
embodiments. The radius of curvature of the mask can be within a
range of from about 7.2 mm to about 8.8 mm in other embodiments.
The radius of curvature of the mask can be within a range of from
about 7 mm to about 9 mm in other embodiments. In some embodiments,
the radius of curvature of the mask can be less than 7 mm. In other
embodiments, the radius of curvature of the mask can be more than 9
mm. The mask can have a thickness between the convex and concave
surfaces of about 10 microns or less or about 7 microns or less.
The dimensions listed in this paragraph illustrate a variety of
examples. Other dimensions and features discussed elsewhere herein
could be substituted for or added to the dimensions discussed in
this paragraph.
[0313] The color of the mask is cosmetically acceptable in one
embodiment for implantation in the human cornea, e.g., having a
black or a dark color appearance at least on an anterior (convex)
side of the annulus.
[0314] The features and performance characteristics discussed above
are largely a function of the materials used to form the masks, the
mask design, and manufacturing techniques used. Applicants have
discovered that some metals are among the materials that can be
configured to exhibit many of these characteristics and that
processes that form thin films (e.g., thin films of metal) are well
suited for making such ocular implants. Physical vapor deposition,
sputtering, electro-depositing and other similar processes
discussed herein are particularly well suited for making ocular
implants of thin metal films. The techniques discussed herein for
forming masks of one or more metal layers can be tailored to reduce
the visibility of the masks and can enhance characteristics related
to longevity, e.g., corrosion resistance.
A. Forming a Mask Using Physical Vapor Deposition
[0315] FIGS. 67a-67d illustrate techniques that can be used to form
a mask or an implant for treating presbyopia, such as one similar
to the masks and implants discussed herein. These techniques
involve forming layers of material, at least one of which is
configured for application to a human eye. As discussed below, the
layers of material can include any combination of one or more of a
release layer, a mask layer, and a sacrificial layer. In some
embodiments, multiple mask layers are provided. As discussed
further below, one or more layer can be configured as a "cosmetic
layer", which is a broad term encompassing a layer or a surface
that provides an appearance desirable to the patient or other
person. A cosmetic layer can reduce the visibility of the mask in
the eye of the patient. A cosmetic layer can also act as a
"non-reflective" layer that reduces the amount of light reflected
off the mask. The cosmetic layer can be a mask layer. As discussed
below, where multiple mask layers are provided (e.g., at least one
cosmetic layer), one or more of the mask layers can be configured
to reduce or prevent corrosion (e.g., galvanic corrosion) of the
mask. Where multiple mask layers are provided (e.g., at least one
cosmetic layer), one or more of the mask layers can be configured
to substantially enhance resistance to galvanic corrosion and other
modes of mask degradation that would compromise the longevity of
the mask. As used herein, the term "sacrificial layer" is a broad
term used in its ordinary sense and includes any layer that is
formed during a method for making a mask that is primarily or
entirely to facilitate other aspects of the method of making and
also includes layers that are entirely or substantially removed
during the process or are not part of the mask. A "release layer"
is a type of sacrificial layer that is intended to facilitate
separating one structure from another, e.g., to separate a mask
from a substrate, as discussed below. Any suitable technique for
forming the layers of material can be exploited. Techniques for
forming layers using thin film sputtering are discussed first. The
materials for forming the mask layer(s), discussed in connection
with thin film sputtering, may also be used with other techniques
for forming the mask layer(s). Other techniques that can be used
are discussed thereafter.
[0316] 1. Thin Film Sputtering
[0317] The applicants have discovered that thin film sputtering is
a convenient technique for making a mask that is capable of being
implanted in a human eye for treating presbyopia. Thin film
sputtering is particularly well suited for making a corneal inlay.
Many thin film sputtering techniques include three steps: 1)
generating atomic or ionic species from a target comprising a metal
or an alloy material; 2) transporting the species from the target
to a substrate through a gas or a plasma medium; and 3) condensing
the species on a surface of a substrate to form a solid thin film.
As discussed below, Argon gas can be used to generate a plasma to
enable these process steps. The target can comprise any metal or
metal alloy and the substrate can comprise a polished silicon or
glass wafer or a wafer of another suitable material. In one
technique, a non-planar substrate is used to form one or more mask
layer, release layer, or sacrificial layer. In another embodiment,
a planar substrate is used to form a layer.
[0318] FIG. 67a is a cross-sectional view of a portion of a
substrate 6000 that can be used in a sputtering process to form a
mask or other thin ocular implant. The substrate 6000 is provided
with a top surface 6004 that includes a mask forming feature 6008.
In one embodiment, the substrate 6000 also includes a planar
portion 6012 that at least partially surrounds the mask forming
feature 6008. The planar portion 6012 is a region of the substrate
6000 that can be located between adjacent mask forming features.
Although adjacent mask forming features are not shown, such
features can be located at regular or non-regular intervals across
the substrate 6000. The substrate 6000 can be configured with any
number of mask forming features 6008 that will fit on the substrate
6000. For example, in some methods, it is advantageous to form one
or two mask forming features 6008 on a substrate. In other
embodiments, it is advantageous to form at least four mask forming
features 6008 on a substrate. Depending on the size of the
substrate and the techniques used, four or more than four mask
forming features 6008 could be formed on a substrate. Other
techniques permit sixteen, thirty-two, sixty-four or more mask
forming features 6008 to be formed on a substrate. In a four inch
square substrate, as many as one-hundred-forty-four or more mask
forming features 6008 could be formed on the substrate. The
arrangement of adjacent mask forming features could use any packing
method, e.g., similar to an efficient crystal packing
arrangement.
[0319] The mask forming feature 6008 can be configured such that
later process steps produce a mask shaped to conform to the portion
of the ocular anatomy where the mask is to be implanted. For
example, the mask forming feature 6008 can comprise a curved
profile 6016 that corresponds to the curvature of a layer of the
cornea, or other ocular feature. In one embodiment, the mask
forming feature 6008 includes an annular surface 6020 that
surrounds a central axis 6024. In the technique illustrated in
FIGS. 67a-67d, the annular surface 6020 is substantially smooth,
resulting in the formation of a smooth layer, e.g., one without
discontinuities, pores, or apertures within the boundaries of the
annular surface 6020. In other embodiments, the annular surface
6020 is configured to produce micro-perforations, pores, or holes
that form at least a part of a nutrient transport structure similar
to those discussed herein. In other embodiments, the annular
surface 6020 is configured to produce a desired surface condition
of a mask formed thereon that correlates to a desired blending
characteristic. The mask forming feature 6008 also includes a
central region 6028 which is centered on the central axis 6024 in
one embodiment.
[0320] FIG. 67a shows the profile of the annular surface 6020 at a
section plane that extends through the center of the mask forming
feature 6008 and that includes the central axis 6024. The profile
of the annular surface 6020 includes a first curved profile 6016a
and a second curved profile 6016b. The first and second curved
profiles 6016a, 6016b have generally the same arcuate length and
curvature in one embodiment. The annular surface 6020 can be
configured to form micro-perforations or pores that form at least a
part of a nutrient transport structure. For example, the profiles
6016a, 6016b can include a nutrient transport forming feature, such
as one or more discontinuities, depressions, holes, or wells that
are configured to prevent or substantially prevent bridging across
the nutrient transport forming feature in a layer formed above the
profiles. In this context, "substantially prevent" means that any
bridging that occurs across the nutrient transport forming feature
is removable by a later process that will not damage the layer near
the feature.
[0321] In one technique, holes are provided that have a diameter
selected to provide an appropriate aspect ratio for nutrient
transport features in the mask. For example, the diameter of the
holes can be any diameter that provides a ratio of hole size (e.g.,
diameter) divided by layer thickness that is greater than one. In
another technique, the diameter of the holes is selected to provide
a ratio of hole size (e.g., diameter) divided by layer thickness
that is about one. Nutrient transport structures can be formed in
other ways, e.g., using photolithography, as discussed below.
[0322] The annular surface 6020 can be configured to form a mask
with an anterior surface having a selected surface condition. For
example, one technique produces a mask with a surface roughness
that produces a desired blending characteristic. A blending
characteristic is a characteristic that makes an implant partially
or completely non-observable by persons other than the patient.
Some materials that can be used in the techniques discussed below
to form a mask from one or more layers of thin metal can be made to
appear darker by increasing the roughness of a surface that is
visible when the mask is implanted, e.g., the anterior surface. In
some techniques, in addition to roughening the surface of a mask, a
cosmetic layer can be applied to provide a desirable visual
appearance, e.g., to further reduce the visibility of the mask. As
discussed further below, the cosmetic layer can have additional
utility, such as providing or enhancing corrosion resistance. The
roughness of an anterior surface of a mask can be increased by
increasing the roughness of the annular surface 6020.
[0323] The mask forming feature 6008 can be configured to define
one or more edges of a mask formed on the annular surface 6020 in a
later process stage. In one embodiment, the annular surface 6020
has an inner periphery 6032 and an outer periphery 6036. The inner
and outer periphery 6032, 6036 of the annular surface 6020
correspond to an inner and an outer periphery of a mask formed on
the annular surface 6020 in a later process stage. One or both of
the inner and outer peripheries 6032, 6036 can be eliminated in
some techniques. For example, forming a mask on the substrate 6000
can be combined with a process for defining an inner periphery of a
mask, an outer periphery of a mask, or both an inner and an outer
periphery of a mask. In one technique, the inner periphery 6032 is
eliminated. After a mask has been formed, an inner periphery of the
mask can be formed using any suitable technique, e.g., machining,
cutting, laser drilling or laser cutting. In one technique, a sheet
of masks formed on a plurality of mask forming features 6008 is
mounted to a fixture and a laser indexes from one mask to the next
cutting out a central portion to define an inner periphery. The
outer periphery 6036 can be eliminated in another technique where
it is desirable to form a mask locator structure that extends from
an outer periphery of a mask. After one or more masks have been
formed in this manner, a laser or other machining implement can be
operated to act on the mask to define an outer periphery of the
mask and/or a locator structure. The outer periphery 6036 also
could be modified such that a locator structure could be defined
during the formation of a mask on the substrate. For example, the
outer periphery 6036 could include a substantially circular portion
and an elongated portion that extends outwardly from the
substantially circular portion. More details of masks with locator
structures that could be formed using this or a similar technique
are discussed in an application filed Apr. 14, 2005 bearing the
title "Ocular Inlay With Locator" (Attorney Docket No.
ACUFO.024A).
[0324] In one embodiment, the inner periphery 6032 is a
substantially circular periphery. In one embodiment, the outer
periphery 6036 is a substantially circular periphery. In one
embodiment, both the inner and outer periphery 6032, 6036 are
substantially circular and are centered on the central axis 6024.
In some embodiments, the inner and outer peripheries 6032, 6036
have different shapes, e.g., a circular inner periphery and a
non-circular outer periphery, a non-circular inner periphery and a
circular outer periphery, etc. In another embodiment, at least one
of the inner and outer periphery 6032, 6036 is not centered on the
central axis 6024. For example, in one embodiment, the inner and
outer periphery are circular but at least one of the inner and
outer periphery 6032, 6036 is not centered on the central axis
6024. As a result, the annular surface 6020 (and the mask formed
thereon at a later stage) can be asymmetrical about the central
axis 6024 in some embodiments. The inner and outer periphery 6032,
6036 can have other configurations such that the annular surface
6020 (and the mask formed thereon at a later stage) has other
shapes. Other shapes for the annular surface 6020 that correspond
to the mask designs described herein can be provided.
[0325] The substrate 6000 can comprise a wafer of silicon, a glass
or Pyrex slide, a wafer of ceramic material, or any other suitable
material or arrangement. The size of the substrate 6000 is not
critical, and can be any size practical for processing through a
sputter process chamber. A typical circular substrate wafer size is
4'' diameter, though other sizes can be used.
[0326] In one embodiment, the mask forming feature 6008 includes an
annular inner recess 6040 and an annular outer recess 6044 formed
in the substrate 6000. The inner recess 6040 is a U-shaped well or
channel having a transverse dimension that extends from the inner
periphery 6032 of the annular surface 6020 toward the central axis
6024 in one embodiment. The outer recess 6044 is a U-shaped well or
channel having a transverse dimension that extends from the outer
periphery 6036 of the annular surface 6020 away from the central
axis 6024 in one embodiment. The inner recess 6040 and outer recess
6044 may be formed in any of a variety of ways such as mechanical
grinding or chemical etching.
[0327] The width and the depth of the inner and outer recesses
6040, 6044 are selected to be large enough to prevent material
layers formed in later stages from bridging or extending across the
recesses 6040, 6044. One technique for preventing bridging is to
provide that the width of the recesses 6040, 6044 is approximately
equal to the thickness of a layer to be formed on the substrate
6000. Another technique for preventing bridging is to provide that
the width of the recesses 6040, 6044 is greater than the thickness
of a layer to be formed on the substrate 6000. The inner and outer
recesses 6040, 6044 enable layers of material to be deposited on
the substrate 6000 in the desired shape, e.g., defining the inner
and outer periphery of a mask at a later stage. This arrangement
enables a mask to be deposited (formed) substantially in the same
shape in which it is to be implanted. This advantageously
eliminates later process steps of defining the inner and outer
periphery of the mask. Other processes described below employ
additional steps to define at least one aspect of a mask, e.g., its
inner or outer periphery or curvature.
[0328] The dimensions of the inner and outer periphery 6032, 6036
and the curvature of the first and second curved profiles 6016a,
6016b preferably are selected to correspond to the inner and outer
dimensions and the curvature of a mask respectively. These
dimensions are discussed above in connection with the various masks
described herein. In one embodiment, the inner and outer periphery
6032, 6036 of the mask forming feature 6008 have the same
dimensions as a mask to be formed thereon and the curvature of the
first and second curved profiles 6016a, 6016b are the same as the
desired curvature of the mask to be formed thereon.
[0329] In one embodiment, the mask forming feature 6008 protrudes
from the top surface 6004 of the substrate 6000. In this
arrangement, the mask forming feature 6008 presents a convex
surface upon which a material layer may be formed. As discussed
below, a release layer, a mask layer, a sacrificial layer, or
another material layer may be formed on the convex surface of the
mask forming feature 6008 or on a layer of material formed on the
convex surface. FIG. 67a shows that in one embodiment, the first
and second curved profiles 6016a, 6016b are convex curved
profiles.
[0330] In one variation, a mask is initially formed in a flat
configuration on a planar top surface of a substrate that is
otherwise similar to the substrate 6000. This variation may be used
to form a mask that is sufficiently flexible to conform to an
ocular structure, e.g., a corneal layer, when applied to the
structure, and thus does not require any preformed shape. In some
techniques, one or more further steps are performed (such as
thermoforming or compression, depending upon the mask material) to
shape the mask to conform to an ocular structure after the mask is
formed on the planar top surface.
[0331] In one variation of the mask forming feature 6008, a
continuous imperforate curved profile is provided by eliminating
the inner recess 6040. As discussed further below, this arrangement
could be used in a process wherein an inner periphery of a mask is
defined after sputtering. The inner periphery of a mask can be
defined by cutting a central region out of the mask. Any suitable
technique can be used to cut out the central region. For example,
the central region could be cut out by a laser cutting process.
Laser cutting can be used to otherwise further define a mask, e.g.,
by separating a mask from a neighboring mask or by forming nutrient
transport apertures in a portion of a mask.
[0332] In another variation, the mask forming feature 6008 includes
a concave surface upon which a mask can be formed. In this
arrangement, the mask forming feature 6008 includes a recess in the
top surface 6004 of the substrate 6000. As discussed further below,
a mask can be formed on the substrate 6000 with one surface of the
mask exposed, e.g., with one surface of the mask not in contact
with the substrate 6000 or with any layer between the substrate
6000 and the mask.
[0333] The substrate 6000 can be prepared using any technique that
will facilitate the formation of thin film layers thereon. For
example, the top surface 6004 can be cleaned and polished to
facilitate sputtering processes, as described below, or other mask
forming processes. In one technique, the substrate 6000 is cleaned
at an elevated temperature using a cleaning solution or agent for a
fixed period. For example, the substrate 6000 can be cleaned in an
RCA cleaning solution (e.g., a mixture of ammonium hydroxide,
hydrogen peroxide and DI water in the ratio of 1:1:5 respectively)
at 80 degrees Celsius for 30 minutes to remove impurities such as
grease and dust particles. Alternatively, other cleaning solutions
can be used, such as Micro-90 (a commercially available mixture of
salts of sodium, ammonium and acids). In another technique,
discussed above, the substrate 600 is prepared by providing a
roughness level that is selected to provide a desired blending
characteristic.
[0334] As discussed above, sputtering is an advantageous method of
forming thin layers of material on a substrate for forming an
ocular implant. Sputtering is usually performed in a vacuum or very
low pressure and so a process chamber is normally provided in which
the substrate 6000 can be mounted. In one technique, the substrate
6000 is mounted on a table that is rotated during the process.
Rotation of the substrate results in a more uniform deposition of
material, providing a more uniform thickness, for example. The
process chamber preferably also is configured to receive a target
comprising a target material. In some arrangements, the process
chamber is capable of accommodating multiple targets so that
different materials can be sputtered, if needed. Preferably the
process chamber is capable of multiple sputtering modes, for
example enabling sputtering from one or all the targets in one or
both of a radio frequency (RF) sputtering mode and a direct current
(DC) sputtering mode.
[0335] In one sputtering technique, a vacuum in the range of low
10.sup.-7 torr is induced in the process chamber by one or more
vacuum pumps, which can be a mechanical pump, cryo pump or turbo
molecular pump. Argon gas (or other inert gas) at a low pressure
(around a few millitorr) is introduced into the chamber. Thereafter
a high voltage from a DC or an RF power supply is applied to the
target material to create a glow discharge. The glow discharge
dissociates the argon atoms into a cloud of ions called a plasma.
The ions in the plasma can be accelerated toward the target
material. Collision of the ions with the target causes atoms of the
target material to be dislodged from the surface of the target.
Thereafter, the dislodged atoms condense on the exposed surfaces of
the substrate 6000. As the amount of atoms that are condensed on
the substrate 6000 increases, a thin film of the material forms on
the substrate 6000.
[0336] FIG. 67b illustrates a later stage of a method for making a
mask in which a release layer 6080 has been formed on the mask
forming feature 6008 of the substrate 6000. As discussed above, a
release layer is a type of sacrificial layer that facilitates the
separation of a mask from the substrate 6000. The release layer
6080 can be formed using the sputtering process described above or
any suitable variation thereof. In one technique, the release layer
6080 is formed by using a target comprised of a material that can
be eroded away by another process, e.g., by etching, without
damaging other layers that form a part of or are coupled with a
mask. The material used to form the release layer 6080 may be a
metal, such as chromium, aluminum, copper, TiCuAg, 90% tungsten 10%
titanium (released with hydrogen peroxide), or any other metal or
alloy. Other materials can be used if the release layer is to
enable separation of mask layers from the substrate 6000 by a
non-erosion process.
[0337] In one embodiment, the release layer 6080 is sputter
deposited to a thickness of about 500 .ANG. or more on the
substrate 6000. The release layer 6080 can be sputter deposited
using RF sputtering at argon pressure of about 2 millitorr. The
thickness of the release layer 6080 can vary. For example, the
release layer could have a thickness of a few hundred angstroms, a
thickness less than 500 .ANG., a thickness of more than about 500
.ANG., a thickness of a thousand angstroms, or more.
[0338] FIG. 67b shows that the arrangement of the mask forming
feature 6008 prevents the release layer 6080 from bridging from the
planar portion 6012 to the annular surface 6020 and from the
annular surface 6020 to the central region 6028. This aspect of the
mask forming feature 6008 facilitates separation of a mask formed
at a later stage of the process from the substrate 6000 because the
mask can be released from the inner periphery and from the outer
periphery of the mask forming feature 6008. In some techniques, the
planar portion 6012, annular surface 6020, and central region 6028
are not fully isolated from each other and the process for
separating the mask from the mask forming feature 6008 operates
primarily from one of the inner periphery 6032 and the outer
periphery 6036.
[0339] FIG. 67c shows that after the release layer 6080 is formed
on the substrate 6000, a mask layer 6100 can be formed on the
release layer 6080. FIG. 67c should not be taken to suggest that no
other process steps are performed between formation of the release
layer 6080 and the mask layer 6100. For example, in some
techniques, the release layer 6080 is modified prior to formation
of the mask layer 6100. It may be desirable to modify the release
layer 6080 so that it has a desired thickness, e.g., by removing a
portion of the release layer 6080. For example, the average
thickness of the release layer 6080 could be reduced across the
entire mask forming feature 6008. In another example, the thickness
of the release layer 6080 could be reduced at a selected location
of the mask forming feature 6008. The mask layer 6100 can be formed
by any suitable technique, such as one of the sputtering processes
discussed above or a variation thereof.
[0340] In one technique, a mask for treating an ocular ailment,
such as presbyopia or an aberration, is entirely or substantially
entirely formed by a sputtering or other vapor deposition process.
As used in this context, "substantially entirely formed" means that
at least the entire thickness of the mask is formed by this process
and that further steps do not add thickness to the mask, but may
reduce the thickness, form cutouts in the mask, and form the mask.
As discussed further below, in one variation, the mask layer 6100
can be a layer configured to facilitate handling of a mask formed
by the processes described herein or to facilitate application of
such a mask to an eye of a patient.
[0341] In one technique, the mask is substantially entirely formed
by the process, e.g., the mask layer 6100 forms the mask. In this
technique, the mask layer 6100 preferably is able to substantially
improve the patient's vision. The mask layer 6100 preferably is
made to be at least partially opaque. The mask layer 6100
preferably is sufficiently stable to environmental conditions, such
as UV radiation. The mask layer 6100 preferably is sufficiently
biocompatible so that it can be implanted in an eye of a human. A
variety of metals have these properties and are capable of being
formed as thin structures that can be applied to the eye, e.g., as
corneal inlays. For example, nitinol or TiNi and other derivative
alloys of TiNi, gold, tantalum, platinum, titanium (e.g., titanium
6 aluminum 4 vanadium), and stainless steel are believed to have
these properties and to be able to perform well in ocular
applications. The mask layer 6100 can be formed of any of these
materials or of any other suitable biocompatible material.
[0342] The biocompatible material can also be selected from a class
of materials that will not corrode or otherwise degrade during the
useful life of the mask 6200. Selection of such a material to form
the mask layer 6100 is one technique for configuring a surface of a
mask to not corrode. As discussed below, such materials include
noble metals generally and in particular those noble metals
specifically described herein. As discussed further below, another
technique for configuring a surface of a mask to not corrode
involves forming a second layer, which may be a cosmetic layer, on
the mask layer 6100 where the second layer is formed of a material
selected to prevent corrosion or to substantially reduce the
likelihood that the mask will corrode or otherwise degrade when the
mask is applied to the patient.
[0343] As discussed above, a process chamber can be provided with
multiple targets, e.g., one for a mask layer and another for a
release layer. Three or more targets can be provided, e.g., a
release layer target, a first mask layer target, and a second mask
layer target. In one embodiment, discussed further below, the first
mask layer can comprise the majority of the mask and the second
layer can comprise a cosmetic layer, which can be relatively thin.
In another technique, the release layer 6080 and the mask layer
6100 are formed using different modes of the chamber. For example,
the mask layer 6100 can be sputtered using DC sputtering and the
release layer 6080 using RF sputtering. A mask layer comprising an
alloy material can be sputtered from a single alloy target or by
co-sputtering from multiple targets. In another technique, the mask
layer 6100 and the release layer 6080 are sputtered in separate
chambers.
[0344] In one technique, the substrate 6000 is loaded into a
process chamber and a vacuum is induced in the chamber in a low
10.sup.-7 torr range. After the release layer 6080 is formed on the
substrate 6000, the mask layer 6100 is sputter deposited on top of
the release layer 6080 using DC sputtering at an argon pressure of
about 2 millitorr. The mask layer 6100 can be sputtered to any
desirable thickness, e.g., any of the thicknesses of the mask 3000
discussed above.
[0345] Further description of various sputtering techniques is set
forth in U.S. Pat. No. 5,061,914, issued Oct. 29, 1991, U.S. Pat.
No. 6,790,298, issued Sep. 14, 2001, U.S. Pat. No. 6,533,905,
issued Mar. 18, 2003, and US Patent Application Pub. No. US
2003/0059640, published Mar. 27, 2003, each of which is expressly
incorporated by reference herein in its entirety.
[0346] Other deposition techniques that may be used to form a mask
layer, a release layer, or a sacrificial layer include vapor
deposition, vacuum evaporation, molecular beam epitaxy, evaporative
deposition, pulsed laser deposition, ion plating, ion implantation,
and laser surface alloying. Other types of vapor deposition and
other techniques for forming layers are discussed below.
[0347] FIG. 67d illustrates a technique for separating a mask 6200
formed by the process discussed in connection with FIGS. 67a-67c
from a substrate 6000. As discussed above, the release layer 6080
is a sacrificial layer, e.g., a layer that facilitates the
formation of the mask 6200 and that is substantially or entirely
removed from the mask 6200 during the process of making the mask
6200. The mask 6200 may be separated from the substrate 6000 by any
suitable technique. In one technique, the release layer 6080 is
eroded away so that a gap forms between the annular surface 6020
and the mask 6200. When the release layer 6080 is fully eroded, the
mask 6200 is entirely separated from the substrate 6000. As
discussed above, the inner and outer recesses 6040, 6044 enable the
process of eroding the release layer 6080 to proceed from both
sides of the annular surface 6020. This may significantly shorten
the process time for separating the mask 6200 from the substrate
6000.
[0348] In one technique, the substrate 6000 with the release and
mask layers 6080, 6100 formed thereon is immersed in a bath
containing an agent capable of eroding the release layer 6080, as
discussed above. The agent may be a chemical that will selectively
etch the release layer 6080 but have no harmful effect on the mask
layer 6100. Preferably, the etchant or other chemical or agent used
to release the layer 6100 from the substrate 6000 does not react
strongly with the layer 6100. In one technique, the release layer
6080 is formed of chromium and the mask is separated from the
substrate by contacting the release layer 6080 with a chromium
etchant. For example, the chromium release layer can be submerged
in a chromium etching bath. Although chromium and other release
layer material have been discussed herein, one skilled in the art
will recognize that a wide variety of materials could be used as a
release layer and an agent for separating a device layer from a
substrate.
[0349] FIG. 67d shows that separating the mask 6200 from the
substrate 6000 generates one or more pieces of scrap material 6204,
which may correspond to material deposited at the same time as the
mask layer 6100. The scrap material 6204 is separated from the mask
6200 and discarded.
[0350] FIG. 68 illustrates a mask 6300 that can be formed by a
method where the mask is configured to not corrode. FIG. 68 also
illustrates a mask that can be formed by a method where the mask is
configured to be inert. In one variation, the mask 6300 is formed
with two or more separate layers to provide desirable
characteristics. For example, as discussed further below, one layer
can be formed of a material that has advantageous properties for
minimally invasive implantation and a second layer can be formed as
a cosmetic layer, providing a suitable visual appearance. The
method for forming the mask 6300 is similar to the method
illustrated in FIGS. 67a-67d, except as described differently
below.
[0351] The mask 6300 includes a first mask layer 6304 and a second
mask layer 6308. The first mask layer 6304 can be formed using any
suitable technique, including those described herein. For example,
the first mask layer 6304 can be formed on a substrate that can be
similar to the substrate 6000 of FIGS. 67a-67d or any suitable
variation thereof. Like the masks described above, the mask 6300
has an anterior surface 6312 and a posterior surface. The posterior
surface is not shown, but is on the opposite side of the mask 6300
from the anterior surface 6312. In a multi-layer device, the
anterior surface can be any surface or interface between layers
that generally faces forward or out of the eye when applied. The
anterior surface can be a surface that contacts a corneal layer
when the mask 6300 is applied. In one embodiment, the anterior
surface 6312 is a surface located internally in the mask 6300. For
example, the anterior surface 6312 can be located at an interface
between the first and second layers 6304, 6308. The anterior
surface can be an external surface of the mask 6300.
[0352] The first and second mask layers 6304, 6308, may take any
suitable form. The first and second mask layers 6304, 6308 can be
formed of the same or different materials. In one embodiment, the
first mask layer 6304 is formed of a first material that is
selected to have any of the advantageous mask properties described
above. The second mask layer 6308 can be formed of a second
material selected or configured to have any of the advantageous
cosmetic or visual properties described above.
[0353] Where the first and second materials are different
materials, the combination of materials used for the first and
second mask layers 6304, 6308, should be carefully selected. This
is particularly true where the selection of materials could cause a
potentially destabilizing reaction to occur. For example, where
there is sufficient galvanic potential between the first layer 6304
and the second layer 6308, corrosion could occur along the
interface.
[0354] To prevent mask degradation of this type, a surface of the
mask 6300 can be configured to not corrode by selecting a first
material for the first mask layer 6304 and a second material for
the second mask layer 6308 where the first and second materials
have similar galvanic potential. In another technique, a third
layer (not shown) configured to prevent the material of the first
mask layer 6304 from interacting chemically or otherwise with the
second mask layer 6308 may be formed between the first and second
mask layers 6304, 6308. For example, the third layer may be formed
of an interface material that at least substantially prevents
electrical communication between the first and second mask layers
6304, 6308. The interface material could be a suitable polymer or
another insulating material. The third layer could provide
additional functionality, such as providing mechanical coupling
between the first and second mask layers 6304, 6308. Accordingly,
the third layer may be a layer of adhesive. These and other
techniques for configuring the mask not to corrode are discussed
further below.
[0355] In one embodiment, the first mask layer 6304 could be formed
of a biocompatible metal, as described herein. As discussed above,
noble metals have some advantageous characteristics. For example,
noble metals are more resistant to some processes that could
degrade the mask 6300, such as galvanic reactions. Such reactions
can result if additional layers of material are formed on the first
mask layer 6304 where a galvanic potential between the layers is
created that is sufficient to drive a galvanic reaction. Also,
noble metals are generally slow to react, and in at least this
sense, generally are inert. In particular, as discussed further
below, combining a first layer of a noble metal and a second layer
of carbon provides a mask arrangement that will be substantially
resistant to corrosion due to a galvanic reaction.
[0356] Another class of materials that may be advantageous in some
applications includes materials that have superelastic or shape
memory characteristics. Such materials include nitinol and other
similar alloys of nickel and titanium. Such materials are
particularly well suited for implantation using less invasive
techniques, such as implantation in a pocket. These materials are
advantageous in that they can enable a mask to be folded, rolled,
or otherwise compressed to a relatively low profile so that the
mask can fit through a relatively small incision. As used herein, a
"relatively small incision" is one that is substantially less than
the diameter of a mask. For example, an incision that is about
two-thirds or less than about two-thirds the diameter of a mask is
a relatively small incision in some procedures. In other
procedures, an incision that is about one-half or less than about
one-half the diameter of a mask is a relatively small incision. In
other procedures, an incision that is about one-third or less than
about one-third the diameter of a mask is a "relatively small
incision" in some procedures. By reducing the size of the incision
through which a mask is inserted, the recovery time for the patient
can be shortened.
[0357] FIG. 68 shows the second mask layer 6308 of the mask 6300,
which can be formed after the first layer 6304 is formed in some
processes. The second mask layer 6308 can be formed on a surface of
the first layer 6304. As discussed above, the second layer 6308 can
be formed to provide a desirable visual appearance to persons other
than the patient. The second layer 6308 can be configured to be a
non-reflective layer. A non-reflective layer is useful where the
material forming the first layer 6304 is a shiny material, e.g., a
shiny metal material. Forming a non-reflective second mask layer
can darken the appearance of the mask 6300. By darkening the
appearance of the mask 6300, the presence of the mask 6300 in a
patient's eye can be made less apparent to others.
[0358] In some embodiments, the second layer 6308 can be formed as
a cosmetic layer on the anterior surface 6312 of the mask 6300. As
discussed above, a cosmetic layer can be formed to reduce the
visibility of the implant within the patient's eye. The cosmetic
layer may be tailored for a patient. In one embodiment, the second
layer 6308 is formed as a cosmetic layer that has an appearance
similar to that of the pupil. In other embodiments, a cosmetic
layer can be formed that has a color similar to the color of the
iris near an outer periphery of the mask and that has a color
similar to the color of the pupil near the inner periphery of the
mask.
[0359] As discussed above, another technique for cosmetically
altering the mask 6300 is to roughen a surface that will be visible
when the mask 6300 is applied, e.g., the anterior surface 6312. By
making the surface rougher, the surface becomes less reflective and
therefore less visible in the eye of the patient to others. In
another technique, a mask can be made less visible by both
roughening the anterior surface 6312 and by providing a cosmetic
layer, e.g., on the anterior surface 6312 of a first layer.
[0360] The second layer 6308 may be formed by any suitable process,
such as a depositing process similar to those described herein or a
coating technique.
[0361] As discussed above, noble metals are suitable for forming
the first mask layer 6304. These materials are suitable because
they are relatively inert and are biocompatible. Also, these
materials substantially reduce the likelihood that corrosion will
occur in the presence of carbon, which is one material that can be
used to form the second layer 6308. Carbon is suitable for the
second layer because it blends in with the pupil and thus provides
a desirable cosmetic appearance. Carbon can be formed as the second
layer 6308 by any suitable process. The carbon layer should be
thick enough to provide the desired cosmetic result, e.g., making
the mask 6300 unobtrusive or not visible to others when implanted
in the eye of a patient. In some applications, the thickness of the
second layer 6308 is regulated such that it is not thicker than
necessary to provide the cosmetic effect. This arrangement has the
advantage of maintaining the low profile nature of the mask 6300.
In a low profile configuration, the mask 6300 can be more easily
folded or otherwise handled during implantation procedures. Also,
in a low profile configuration, the mask 6300 will be less likely
to affect the curvature of the anterior surface of the cornea so
that the mask 6300 will not affect the refractive properties of the
cornea in which it is applied. In other applications, the second
mask layer 6308 or the mask 6300 can be thicker, but should not
interfere with the implantability or wearability of the mask 6300.
The thickness of the mask can vary and can be any of the
thicknesses discussed herein. The thickness of the second layer
6308 can be a fraction of the overall thickness of the mask 6300,
e.g., one percent or less than the thickness of the mask 6300, one
to ten percent of the thickness of the mask 6300, ten to twenty
percent of the thickness of the mask 6300, twenty to thirty percent
of the thickness of the mask 6300, or more than thirty percent of
the thickness of the mask.
[0362] Carbon can be co-deposited with a noble metal in a
sputtering or in an electro-deposition process, for example. The
carbon layer preferably is formed on a noble metal layer such that
the carbon adheres to the noble metal layer. Nobel metals can be
combined with other suitable materials that can provide suitable
cosmetic appearance, e.g., silicon carbide.
[0363] As discussed above, these and other similar processes can
employ a suitable substrate, e.g., one similar to the substrate
6000, to form one or more masks that are not connected to each
other during the formation of the layers 6304, 6308. In other
techniques, these processes can form a sheet of interconnected
masks on a suitable substrate such that the masks can be separated
from each other during a later processing stage. For example, a
plurality of interconnected masks can be formed by the processes
described herein and later separated from each other by any
suitable process, such as machining, laser cutting, chemical
etching, or another similar process.
[0364] As discussed above, masks can be made of mask layers that
initially are formed flat or with a selected curvature. In one
technique where the mask is made of mask layers that are initially
formed flat, a curvature can be induced in the mask at a later
process stage. For example, a mask can be cup-formed after one or
more layers thereof have been formed in a flat configuration. In
one cup-forming process, a mask is urged into contact with a
shaping surface, which can have a part-spherical contour. In
various embodiments, the shaping surface is a surface of a mold. In
one technique a mold is provided that includes a convex surface and
a concave surface. A mask that has been formed by the techniques
described above can be inserted into the mold in a flat or
non-formed configuration between the convex and concave surfaces.
Thereafter, the convex and concave surfaces are brought into close
proximity, urging the mask into the desired shape.
[0365] After the mask has been urged into contact with a shaping
surface, the mask can be processed further such that the mask
maintains the curvature of the shaping surface. For example, the
mask can be heat treated while being held against one or more
shaping surfaces. In one heat treating technique, the mask is
placed in an elevated temperature environment for a time sufficient
to cause the stress in the material of the mask to be released.
This will result in the mask being in a relaxed state when in the
shape of the mold. In one technique, the mask is placed in an
environment having an elevated temperature of about 500 degrees
Fahrenheit or more. In another technique, the mask is placed in an
environment having an elevated temperature of about 500 degrees
Celsius or more. In one technique, the mask is placed in an
environment having an elevated temperature of about 300 degrees
Fahrenheit or more. In another technique, the mask is placed in an
environment having an elevated temperature of about 300 degrees
Celsius or more. In one technique, the mask is placed in an
environment having an elevated temperature of about 250 degrees
Fahrenheit or more. In another technique, the mask is placed in an
environment having an elevated temperature of about 250 degrees
Celsius or more. After heat treating, the mask will maintain the
shape of the shaping surface without significant strain.
[0366] As discussed above, in some applications it is desirable to
form a mask with multiple layers such that at least one of the
layers has with pores. The pores can be similar to those discussed
above as providing nutrient transport across a mask. As discussed
above, the substrate can be configured to produce porous or smooth
layers for different applications. Porous layers can be produced
using substrate with a pattern of protrusions, for example. In
another technique, one or more process variables can be altered to
produce a mask layer characteristic, such as porosity. For example,
the rate or speed of layer formation, e.g., the rate of
electro-deposition, can be selected to provide a more porous layer.
In one technique, a relatively high rate of electro-deposition
produces a more porous mask layer or mask.
[0367] As discussed above, nitinol and other similar materials are
advantageous in some application. In some techniques, where the
first mask layer 6304 is formed of nitinol, a second material is
selected to form the second mask layer 6308 that will not be
degraded by a chemical or biological reaction, such as galvanic
corrosion. The second material can be selected such that no or an
insubstantial amount of galvanic potential exists between the first
and second mask layers 6304, 6308. One material that can be used
for the second material is titanium oxide. In some environments,
e.g., in the presence of oxygen, titanium oxide will form on an
exposed surface of titanium or a titanium alloy. Thus, the second
layer 6308 also can be formed by exposure to oxygen. A sufficiently
thick layer of titanium oxide formed on the titanium or titanium
alloy surface will passivate the titanium or titanium alloy
surface, e.g., configuring the mask for little or no corrosion at
that surface. Another material that can be used for the second
material is silicon carbide. Other similar materials that can be
combined with nitinol or similar alloys without producing galvanic
corrosion can be selected as the second material.
[0368] In other embodiments, an anterior surface of the mask can be
coated to reduce the visibility of the mask 6300 when applied to a
patient. For example, the anterior surface 6312 could be coated
with at least one of any of the materials discussed above in
connection with the second mask layer 6308, or an organic dye, an
inorganic pigment, or other compounds, such as black iron oxide. In
another variation, the second mask layer 6308 can be formed of a
suitable polymeric material, e.g., a polymeric material that
reduces the reflectivity of the first mask layer 6304. Polymeric
materials are not subject to galvanic reactions. In another
variation, the second mask layer 6308 is formed of a mixture of a
polymeric material and a suitable dye to provide a desirable
cosmetic effect, as discussed herein.
[0369] In some techniques, it may be desirable to darken both the
anterior and posterior surfaces of the mask 6200.
[0370] The process of FIGS. 67a-67d enables a mask to be formed in
substantially the same configuration in which it is to be implanted
in the eye of a patient. As discussed above, this is achieved in
part by providing a substrate with a mask forming feature that is
shaped to correspond to the shape of the ocular anatomy in the
region of the eye where the mask is to be applied. This may be
achieved by providing the mask forming feature with a shape that is
similar to the shape of a layer of corneal tissue where the mask is
to be implanted in the corneal. The process also facilitates
application of the mask to the human eye by being capable of
producing the mask with certain dimensions tightly controlled. For
example, the process enables a mask to be formed that is thin
enough to be implanted in the cornea without adversely affecting
the adjacent corneal tissue.
[0371] As discussed above, one variation of the forgoing method of
making a mask employs a substrate that is similar to the substrate
6000 but that is substantially planar rather than shaped. This
process will form a mask that is similar to the mask 6200, but that
also initially is substantially planar. In some applications, a
substantially planar mask 6200 may be thin enough to be applied to
an eye and to conform to the native anatomy, e.g., to the curvature
of the cornea, when applied. In other applications, it may be
desirable to induce a permanent shape in a mask that was initially
of a planar construction. As used in this context, "induce a
permanent shape" is a broad term and it is used in its ordinary
meaning and it includes forming the mask to retain its shape in the
absence of a force other than gravity. This shape does not prevent
the mask from flexing to an extent when applied to the eye or when
acted on by ocular structures.
[0372] Any suitable process can be used to induce a shape in a
mask. One such process involves placing the mask on or in a
mandrel, engaging the mask with a member to cause it to take on the
desired shape, and heat treating the mask to cause it to maintain
that shape. This process is discussed in more detail in U.S. Pat.
No. 6,746,890, which is hereby expressly incorporated by reference
herein in its entirety.
[0373] As discussed above some masks are configured with nutrient
transport structures that increase the acceptance of the mask by
adjacent tissue. For example, the mask 4400 is formed with holes
that extend from an anterior surface to a posterior surface. Such
holes may be formed by depositing a plurality of layers with holes
formed in them. The location of the holes in adjacent layers can be
important, as discussed above. For example, the location of holes
can reduce the production of diffraction patterns. The
configuration and location and orientation of the holes can be
adequately controlled using sacrificial layers and
photolithography, as is discussed in more detail in U.S. Pat. No.
6,746,890, which is incorporated by reference herein above. Holes,
sometimes referred to herein as "micro-perforations" or
"perforations", can also be formed in a process that provides a
substrate with nutrient transport forming features, as discussed
above.
[0374] As discussed above, one variation of the foregoing process
provides a mask structure that enables a mask to be handled, e.g.,
while being manufactured, shipped, or applied by a surgeon to the
patient's eye. As discussed above, some embodiments of masks
configured to be applied to an eye are very thin. Stated another
way, the structures have a relatively high ratio of surface area to
thickness. This is particularly true where the mask is intended to
be implanted in the cornea of a patient's eye. As a result, a thin
mask can be damaged depending on the skill of the person handling
it. Damage to the mask can include contamination on the surface of
the mask, creases formed in the mask, etc. Such damage at least
increases the processing time (e.g., by requiring additional
cleaning steps) but can also require that the damaged mask be
scrapped. To reduce the likelihood of scrapping of masks, it is
desirable to provide a handling structure, e.g., a layer that is
less easily damaged or that can be damaged without impairing the
performance of the mask.
[0375] In one technique, a handling structure is formed as a
removable mask support layer. The handling structure can be formed
by any process. For example, any of the sputtering processes
described above could be used to form the handling structure. In
one embodiment, the handling structure is formed as a sacrificial
layer. As discussed above, a sacrificial layer is a layer that can
be removed or separated from the mask at some point during the
lifecycle of the mask. The sacrificial handling layer can be made
of the same material as the release layer 6080, the same material
as the mask layer 6100, or another suitable material. The handling
structure can be removed by any process, e.g., by eroding or
etching the layer, or by otherwise separating the handling
structure from the mask. The handling structure can take any
suitable configuration. Preferably the handling structure is
temporarily coupled with the mask or a portion thereof. For
example, the handling structure can be coupled with an outer
periphery of a mask. In one embodiment, the handling structure is
an annular member that surrounds or partially surrounds the mask or
a portion of the mask. The handling structure could be a bar or a
flange of suitable configuration. The handling structure is
configured to be clamped or fixed in a processing device or process
chamber in one embodiment. The handling structure is able to
securely hold a mask during one or more process steps in one
embodiment. The handling structure is removable after the process
for manufacturing the mask is complete or partially complete in one
embodiment.
B. Forming a Mask Using Other Layer Forming Methods
[0376] Other techniques that do not involve sputtering to form a
mask layer can be employed in other techniques or combined with
methods involving physical vapor deposition.
[0377] 1. Chemical Vapor Deposition
[0378] Chemical Vapor Deposition (CVD) may also be used to form the
mask or a portion of the mask. CVD methods include atmospheric
pressure chemical vapor deposition, low pressure chemical vapor
deposition, plasma assisted (enhanced) chemical vapor deposition,
photochemical vapor deposition, laser chemical vapor deposition,
metal-organic chemical vapor deposition, and chemical beam
epitaxy.
[0379] 2. Precipitation Out of a Solution
[0380] A layer, such as a mask layer, release layer, or sacrificial
layer, could be formed by precipitating a material out of a
solution. This technique is analogous to the methods discussed
above in connection with FIGS. 67a-67d, except as set forth
below.
[0381] Mask layers, release layers, sacrificial layers, or other
layers are formed by a precipitate that emerges from a solution.
For example, a solution including metal ions can be prepared and
placed into contact with a substrate. The substrate can be similar
to the substrate 6000. In one technique a tank is provided and the
substrate is placed in the bottom of the tank. A solution with
metal or alloy ions or molecules is then placed in the tank in
contact with the substrate. Thereafter, the solution can be acted
on to cause a metal or alloy ion or molecule to no longer be
soluble in the solution. For example, sufficient quantities of the
desired metal ion can be added to the solution such that the
solubility of that ion within the solution is exceeded. This
condition will cause the metal ion to precipitate out of the
solution and condense onto the substrate 6000. In another example,
the solvent can be evaporated from the solution, increasing the
concentration of the desired metal ion until its solubility is
exceeded, thus causing the ion to precipitate out of the solution
and to condense onto the substrate 6000. Other techniques, such as
altering the pH of the solution can be employed to get the solute
to precipitate out of the solution.
[0382] Once sufficient solute has formed on the substrate, the
solution can be evacuated from the tank and another solution placed
in the tank with the same or a different material or metal ion
solute. In some methods, more than one technique can be combined,
such as using precipitation out of a solution for one layer and
vapor deposition for another layer.
[0383] 3. Electroplating and Electrodepositing
[0384] Other suitable techniques for forming layers that can be
used to form some masks include electroplating or electrodepositing
and electroforming. In one embodiment, forming a mask by
electrodeposition is analogous to the method discussed above,
except as set forth below.
[0385] Electrodeposition is the process of producing a layer or
coating, which can be metallic, on a surface of an object by the
action of electric current. The deposition of a metallic coating
onto an object can be achieved by negatively charging the object to
be coated and immersing the object into a solution that contains a
salt of the metal to be deposited. In this arrangement, the object
to be plated can be the cathode of an electrolytic cell. In one
technique, the object to be plated is similar to the substrate
6000.
[0386] In one technique, the metallic ions of the salt carry a
positive charge and are attracted to the substrate or object. When
the metallic ions reach the negatively charged object, e.g., a
substrate, the substrate provides electrons to reduce the
positively charged ions to metallic form. In electrodepositing and
electroforming, the substrate can be made of any suitable material,
e.g., copper. The material to be plated is one that can be eroded
to separate a mask from the substrate, as discussed above, or a
mask layer. Where the material to be plated is intended to be a
mask layer, the material is selected with the biocompatility and
stability properties discussed above for long implantation life
(e.g., it is opaque, inert, and does not degrade in the presence of
UV radiation).
[0387] In one technique, a conductor is coupled with the substrate
or other object and with a negative pole of a battery (or other
power supply). Another conductor is connected with a positive pole
of the battery (or other power supply) and with an anode of the
electrolytic cell. The anode is analogous to the target, discussed
above in connection with sputtering. Thereafter, a cell is filled
with a solution of the metal salt to be plated. The cell can be a
process chamber. It is possible to use a molten salt (e.g., when
plating tungsten and other similar materials). In some techniques,
the salt is dissolved in water.
[0388] As the substrate or other object to be plated is negatively
charged, it attracts the positively charged cations from the
solution, and electrons flow from the substrate or other object to
the cations to neutralize them (to reduce them) to metallic form.
Meanwhile, negatively charged anions in the solution are attracted
to the positively charged anode. At the anode electrons are removed
from the anode material, oxidizing it to the anode cations. Thus we
see that the anode (analogous to the target, as discussed above)
dissolves as ions into the solution. That is how replacement
cations of the anode/target material are supplied to the solution
for that which has been plated out and one retains a solution of
appropriate composition in the cell.
[0389] One advantage of this technique is that it may be able to
make a porous structure that would at least partially provide
nutrient transport through the mask, as discussed above, without
further process steps. Additional nutrient transport could be
provided by forming additional nutrient transport structures in the
mask using any of the techniques discussed above.
[0390] Although this invention has been disclosed in the context of
certain preferred embodiments and examples, it will be understood
by those skilled in the art that the present invention extends
beyond the specifically disclosed embodiments to other alternative
embodiments and/or uses of the invention and obvious modifications
and equivalents thereof. In addition, while a number of variations
of the invention have been shown and described in detail, other
modifications, which are within the scope of this invention, will
be readily apparent to those of skill in the art based upon this
disclosure. It is also contemplated that various combinations or
sub-combinations of the specific features and aspects of the
embodiments may be made and still fall within the scope of the
invention. Accordingly, it should be understood that various
features and aspects of the disclosed embodiments can be combine
with or substituted for one another in order to form varying modes
of the disclosed invention. Thus, it is intended that the scope of
the present invention herein disclosed should not be limited by the
particular disclosed embodiments described above, but should be
determined only by a fair reading of the claims that follow.
* * * * *