U.S. patent application number 11/618411 was filed with the patent office on 2008-07-03 for pre-stressed haptic for accommodating intraocular lens.
This patent application is currently assigned to Advanced Medical Optics, Inc.. Invention is credited to Daniel G. Brady, Timothy R. Bumbalough, Edward P. Geraghty, Randall L. Woods.
Application Number | 20080161914 11/618411 |
Document ID | / |
Family ID | 39456366 |
Filed Date | 2008-07-03 |
United States Patent
Application |
20080161914 |
Kind Code |
A1 |
Brady; Daniel G. ; et
al. |
July 3, 2008 |
PRE-STRESSED HAPTIC FOR ACCOMMODATING INTRAOCULAR LENS
Abstract
An intraocular lens is disclosed, with an optic that changes
shape in response to a deforming force exerted by the zonules of
the eye. A haptic supports the optic around its equator and couples
the optic to the capsular bag of the eye. The haptic may be
pre-stressed before the optic is placed within it. After such
placement, the pre-stress may be relieved, and the haptic may
produce stress in the optic. The pre-stress may produce a radial
tension or a radial compression in the optic. Alternatively, once
the optic is placed within the haptic, both may undergo a process
that changes the size and/or shape of one with respect to the
other, causing a stress within the optic. This process may produce
a radial tension or a radial compression in the optic. The haptic
may include an annular ring having outer and inner diameters that
may depend on the stiffness of the haptic.
Inventors: |
Brady; Daniel G.; (San Juan
Capistrano, CA) ; Woods; Randall L.; (Sun Lakes,
AZ) ; Bumbalough; Timothy R.; (Fullerton, CA)
; Geraghty; Edward P.; (Rancho Santa Margarita,
CA) |
Correspondence
Address: |
ADVANCED MEDICAL OPTICS, INC.
1700 E. ST. ANDREW PLACE
SANTA ANA
CA
92705
US
|
Assignee: |
Advanced Medical Optics,
Inc.
Santa Ana
CA
|
Family ID: |
39456366 |
Appl. No.: |
11/618411 |
Filed: |
December 29, 2006 |
Current U.S.
Class: |
623/6.46 |
Current CPC
Class: |
A61F 2002/1682 20150401;
A61F 2/1635 20130101 |
Class at
Publication: |
623/6.46 |
International
Class: |
A61F 2/16 20060101
A61F002/16 |
Claims
1. An intraocular lens for implantation into a capsular hag of an
eye, comprising: a stressed optic, and a haptic for coupling the
optic to the capsular bag; wherein the haptic stresses the stressed
optic when the intraocular lens is in a natural state.
2. The intraocular lens of claim 1, wherein the stressed optic is
under tension and the haptic is under compression when the
intraocular lens is in a natural state.
3. The intraocular lens of claim 2, wherein the tension of the
stressed optic and the compression of the haptic are radial and
coaxial.
4. The intraocular lens of claim 1, wherein the stressed optic is
under compression and the haptic is under tension when the
intraocular lens is in a natural state.
5. The intraocular lens of claim 4, wherein the compression of the
stressed optic and the tension of the haptic are radial and
coaxial.
6. An intraocular lens for implantation into a capsular bag of an
eye, comprising: an optic; and a haptic for coupling the optic to
the capsular bag; wherein the optic is under tension when the
intraocular lens is in a natural state.
7. The intraocular lens of claim 6, wherein the haptic is under
compression when the intraocular lens is in a natural state.
8. The intraocular lens of claim 7, wherein the tension in the
optic and the compression in the haptic are radial and coaxial.
9. An intraocular lens for implantation into a capsular bag of an
eye, comprising, an optic having a periphery; and an annular ring
engaging at least a portion of the periphery of the optic for
coupling the optic to the capsular bag; wherein the annular ring
stresses the optic in the absence of an external compressive force
on the annular ring.
10. The intraocular lens of claim 9, wherein the stress on the
optic is tension.
11. The intraocular lens of claim 9, wherein the stress on the
optic is radial.
12. The intraocular lens of claim 9, wherein the annular ring has
an inner radius and an outer radius, the inner and outer radii
being in a ratio that relates to a stiffness of the haptic.
13. An intraocular lens for implantation into a capsular bag of an
eye, comprising: an optic having a periphery; and an annular ring
engaging at least a portion of the periphery of the optic for
coupling the optic to the capsular bag; wherein the optic has a
uncompressed surface profile in the absence of an external
compressive force on the annular ring; wherein the optic has a
compressed surface profile in the presence of an external
compressive force on the annular ring; and wherein the compressed
surface profile is more spherical than the uncompressed surface
profile.
14. An intraocular lens for implantation into a capsular bag of an
eye, comprising. an optic having an equatorial region and a shape,
the shape comprising an anterior curvature and a posterior
curvature; and a haptic for coupling the optic to the capsular bag;
wherein the optic can change its shape in response to essentially
radial forces exerted by the capsular bag and transmitted to the
equatorial region of the optic by the haptic; wherein the haptic is
stiffer than the optic; wherein the haptic is coaxial with the
optic; and wherein the haptic stresses the optic when the
intraocular lens is in a natural state.
15. The intraocular lens of claim 14, wherein the haptic produces
tension in the optic when the intraocular lens is in a natural
state.
16. The intraocular lens of claim 15, wherein the tension in the
optic is radially symmetric.
17. The intraocular lens of claim 15, wherein the tension in the
optic is radially asymmetric.
18. The intraocular lens of claim 14, wherein the haptic protrudes
into the optic.
19. The intraocular lens of claim 14, wherein the haptic comprises
a circumferential ring.
20. The intraocular lens of claim 19, wherein the circumferential
ring of the haptic is disposed within the circumference of the
optic.
21. The intraocular lens of claim 14, wherein the haptic
essentially fills the capsular bag of the eye.
22. The intraocular lens of claim 21, wherein the optic is
disaccommodatively biased.
23. The intraocular lens of claim 14, wherein the optic and haptic
are both transparent.
24. The intraocular lens of claim 14, wherein the optic and haptic
have essentially equal refractive indices.
25. The intraocular lens of claim 14, wherein the optic is made
from silicone.
26. The intraocular lens of claim 14, wherein the haptic is made
from silicone.
27. A method for manufacturing an intraocular lens having a haptic,
comprising: stressing the haptic under an external stress; placing
an optic within the haptic; and removing the external stress from
the haptic, so that at equilibrium, the optic is internally
stressed.
28. The method of claim 27, wherein the stressing step comprises
compressing the haptic.
29. The method of claim 27, wherein the stressing step comprises
tensing the haptic.
30. The method of claim 27, wherein the stressing step comprises
stressing the haptic under a largely radial external stress.
31. The method of claim 27, wherein the stressing step comprises
stressing the haptic under a non-symmetric external stress.
32. The method of claim 27, further comprising changing the
diameter of the haptic between about 0.4% and about 2.0%.
33. The method of claim 27, wherein the placing step comprises
molding the optic directly onto the haptic.
34. The method of claim 27, wherein the placing step comprises
attaching a pre-formed optic to the haptic.
35. The method of claim 27, further comprising supporting the optic
around an equator of the optic.
36. The method of claim 27, further comprising producing an
internal stress in the optic.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention is directed to intraocular lenses, and
more particularly to accommodating intraocular lenses.
[0003] 2. Description of the Related Art
[0004] A human eye can suffer diseases that impair a patient's
vision. For instance, a cataract may increase the opacity of the
lens, causing blindness. To restore the patient's vision, the
diseased lens may be surgically removed and replaced with an
artificial lens, known as an intraocular lens, or IOL. An IOL may
also be used for presbyopic lens exchange.
[0005] The simplest IOLs have a single focal length, or,
equivalently, a single power. Unlike the eye's natural lens, which
can adjust its focal length within a particular range in a process
known as accommodation, these single focal length IOLs cannot
generally accommodate. As a result, objects at a particular
position away from the eye appear in focus, while objects at an
increasing distance away from that position appear increasingly
blurred.
[0006] An improvement over the single focal length IOLs is an
accommodating IOL, which can adjust its power within a particular
range. As a result, the patient can clearly focus on objects in a
range of distances away from the eye, rather than at a single
distance. This ability to accommodate is of tremendous benefit for
the patient, and more closely approximates the patient's natural
vision than a single focal length IOL.
[0007] When the eye focuses on a relatively distant object, the
lens power is at the low end of the accommodation range, which may
be referred to as the "far" power. When the eye focuses on a
relatively close object, the lens power is at the high end of the
accommodation range, which may be referred to as the "near" power.
The accommodation range or add power is defined as the near power
minus the far power. In general, an accommodation range of 2 to 4
diopters is considered sufficient for most patients.
[0008] The human eye contains a structure known as the capsular
bag, which surrounds the natural lens. The capsular bag is
transparent, and serves to hold the lens. In the natural eye,
accommodation is initiated by the ciliary muscle and a series of
zonular fibers, also known as zonules. The zonules are located in a
relatively thick band mostly around the equator of the lens, and
impart a largely radial force to the capsular bag that can alter
the shape and/or the location of the natural lens and thereby
change its effective power.
[0009] In a typical surgery in which the natural lens is removed
from the eye, the lens material is typically broken up and vacuumed
out of the eye, but the capsular bag is left intact. The remaining
capsular bag is extremely useful for an accommodating intraocular
lens, in that the eye's natural accommodation is initiated at least
in part by the zonules through the capsular bag. The capsular bag
may be used to house an accommodating IOL, which in turn can change
shape and/or shift in some manner to affect the power and/or the
axial location of the image.
[0010] The IOL has an optic, which refracts light that passes
through it and forms an image on the retina, and a haptic, which
mechanically couples the optic to the capsular bag. During
accommodation, the zonules exert a force on the capsular bag, which
in turn exerts a force on the optic. The force may be transmitted
from the capsular bag directly to the optic, or from the capsular
bag through the haptic to the optic.
[0011] A desirable optic for an accommodating IOL is one that
distorts in response to a squeezing or expanding radial force
applied largely to the equator of the optic (i.e., by pushing or
pulling on or near the edge of the optic, circumferentially around
the optic axis). Under the influence of a squeezing force, the
optic bulges slightly in the axial direction, producing more
steeply curved anterior and/or posterior faces, and producing an
increase in the power of the optic. Likewise, an expanding radial
force produces a decrease in the optic power by flattening the
optic. This change in power is accomplished in a manner similar to
that of the natural eye and is well adapted to accommodation.
Furthermore, this method of changing the lens power reduces any
undesirable pressures exerted on some of the structures in the
eye.
[0012] One challenge in implementing such an optic is designing the
optic so that it does not distort undesirably anywhere in the
accommodation range. More specifically, while a change in surface
curvature may be desirable for causing a change in optical power,
irregularities on one or both surfaces of the optic may undesirably
lead to optical aberrations or artifacts and thereby degrade the
performance of the optic.
[0013] Accordingly, there exists a need for an intraocular lens
having an optic with an increased resistance to undesirable surface
irregularities during accommodation.
SUMMARY OF THE INVENTION
[0014] An embodiment is an intraocular lens for implantation into a
capsular bag of an eye, comprising a stressed optic; and a haptic
for coupling the optic to the capsular bag. The haptic stresses the
stressed optic when the intraocular lens is in a natural state.
[0015] A further embodiment is an intraocular lens for implantation
into a capsular bag of an eye, comprising an optic; and a haptic
for coupling the optic to the capsular bag. The optic is under
tension when the intraocular lens is in a natural state.
[0016] A further embodiment is an intraocular lens for implantation
into a capsular bag of an eye, comprising an optic having a
periphery; and an annular ring engaging at least a portion of the
periphery of the optic for coupling the optic to the capsular bag.
The annular ring stresses the optic in the absence of an external
compressive force on the annular ling.
[0017] A further embodiment is an intraocular lens for implantation
into a capsular bag of an eye, comprising an optic having a
periphery; and an annular ring engaging at least a portion of the
periphery of the optic for coupling the optic to the capsular bag.
The optic has a uncompressed surface profile in the absence of an
external compressive force on the annular ring. The optic has a
compressed surface profile in the presence of an external
compressive force on the annular ring. The compressed surface
profile is more spherical than the uncompressed surface
profile.
[0018] A further embodiment is an intraocular lens for implantation
into a capsular bag of an eye, comprising an optic having an
equatorial region and a shape, the shape comprising an anterior
curvature and a posterior curvature; and a haptic for coupling the
optic to the capsular bag. The optic can change its shape in
response to essentially radial forces exerted by the capsular bag
and transmitted to the equatorial region of the optic by the
haptic. The haptic is stiffer than the optic. The haptic is coaxial
with the optic. The haptic stresses the optic when the intraocular
lens is in a natural state.
[0019] A further embodiment is a method for manufacturing an
intraocular lens having a haptic, comprising stressing the haptic
under an external stress; placing an optic within the haptic; and
removing the external stress from the haptic, so that at
equilibrium, the optic is internally stressed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a cross-section drawing of a human eye with an
implanted intraocular lens, focused on a relatively close
object.
[0021] FIG. 2 is a cross-section drawing of a portion of a human
eye with an implanted intraocular lens, focused on a relatively
distant object.
[0022] FIG. 3 is a flow chart of a manufacturing process that may
induce an internal stress to the optic.
[0023] FIG. 4 is an end-on drawing of a haptic and optic, shown
throughout various stages of construction.
[0024] FIG. 5 is an isometric drawing of the haptic and optic of
FIG. 4, only with the lens in the plane of the page and the optical
axis of the lens being perpendicular to the page.
[0025] FIG. 6 is an end-on drawing of a haptic and optic, shown
throughout various stages of construction.
[0026] FIG. 7 is an isometric drawing of the haptic and optic of
FIG. 5, only with the lens in the plane of the page and the optical
axis of the lens being perpendicular to the page.
[0027] FIG. 8 is a schematic drawing of an optic and a haptic under
compression from an asymmetric external force.
[0028] FIG. 9 is a schematic drawing of the haptic and optic of
FIG. 8 removed from the asymmetric external force.
[0029] FIG. 10 is a flow chart of a manufacturing process that may
induce an internal stress to the optic.
[0030] FIG. 11 is an isometric drawing of an optic placed within a
haptic.
[0031] FIG. 12 is a cross-section drawing of a haptic.
[0032] FIG. 13 is a cross-sectional drawing of the haptic of FIG.
12, with an optic.
[0033] FIG. 14 is the cross-section drawing of the haptic and optic
of FIG. 13, with additional hidden lines.
[0034] FIG. 15 is an end-on cross-sectional drawing of the haptic
and optic of FIG. 13.
[0035] FIG. 16 is a plan drawing of the haptic of FIG. 12.
[0036] FIG. 17 is a plan drawing of the haptic of FIG. 16, with an
optic.
[0037] FIG. 18 is the cross-section drawing of the haptic and optic
of FIG. 17, with additional hidden lines.
[0038] FIG. 19 is a plan drawing of a haptic.
[0039] FIG. 20 is a plan drawing of the haptic of FIG. 19, with an
optic.
[0040] FIG. 21 is the plan drawing of the haptic and optic of FIG.
20, with additional hidden lines.
[0041] FIG. 22 is a top-view plan drawing of a haptic with an
optic.
[0042] FIG. 23 is a side-view plan drawing of the haptic and optic
of FIG. 22.
[0043] FIG. 24 is a side-view cross-sectional drawing of the haptic
and optic of FIG. 22.
[0044] FIG. 25 is a plan drawing of the haptic and optic of FIG.
22.
[0045] FIG. 26 is a cross-sectional drawing of the haptic and optic
of FIG. 22.
DETAILED DESCRIPTION OF THE DRAWINGS
[0046] In a healthy human eye, the natural lens is housed in a
structure known as the capsular bag. The capsular bag is driven by
a ciliary muscle and zonular fibers (also known as zonules) in the
eye, which can compress and/or pull on the capsular bag to change
its shape. The motions of the capsular bag distort the natural lens
in order to change its power and/or the location of the lens, so
that the eye can focus on objects at varying distances away from
the eye in a process known as accommodation.
[0047] For some people suffering from cataracts, the natural lens
of the eye becomes clouded or opaque. If left untreated, the vision
of the eye becomes degraded and blindness can occur in the eye. A
standard treatment is surgery, during which the natural lens is
broken up, removed, and replaced with a manufactured intraocular
lens. Typically, the capsular bag is left intact in the eye, so
that it may house the implanted intraocular lens.
[0048] Because the capsular bag is capable of motion, initiated by
the ciliary muscle and/or zonules, it is desirable that the
implanted intraocular lens change its power and/or location in the
eye in a manner similar to that of the natural lens. Such an
accommodating lens may produce improved vision over a lens with a
fixed power and location that does not accommodate.
[0049] FIG. 1 shows a human eye 10, after an accommodating
intraocular lens has been implanted. Light enters from the left of
FIG. 1, and passes through the cornea 11, the anterior chamber 12,
the iris 13, and enters the capsular bag 14. Prior to surgery, the
natural lens occupies essentially the entire interior of the
capsular bag 14. After surgery, the capsular bag 14 houses the
intraocular lens, in addition to a fluid that occupies the
remaining volume and equalizes the pressure in the eye. The
intraocular lens is described in more detail below. After passing
through the intraocular lens, light exits the posterior wall 15 of
the capsular bag 14, passes through the posterior chamber 24, and
strikes the retina 16, which detects the light and converts it to a
signal transmitted through the optic nerve 17 to the brain.
[0050] A well-corrected eye forms an image at the retina 16. If the
lens has too much or too little power, the image shifts axially
along the optical axis away from the retina, toward or away from
the lens. Note that the power required to focus on a close or near
object is more than the power required to focus on a distant or far
object. The difference between the "near" and "far" powers is known
typically as the add power or the range of accommodation. A normal
range of accommodation is about 3 to 4 diopters, which is
considered sufficient for most patients.
[0051] The capsular bag is acted upon by the ciliary muscle 25 via
the zonules 18, which distort the capsular bag 14 by stretching it
radially in a relatively thick band about its equator.
Experimentally, it is found that the ciliary muscle 25 and/or the
zonules 18 typically exert a total ocular force of up to about 10
grams of force, which is distributed generally uniformly around the
equator of the capsular bag 14. Although the range of ocular force
may vary from patient to patient, it should be noted that for each
patient, the range of accommodation is limited by the total ocular
force that can be exert. Therefore, it is highly desirable that the
intraocular lens be configured to vary its power over the full
range of accommodation, in response to this limited range of ocular
forces. In other words, it is desirable to have a relatively large
change in power for a relatively small driving force.
[0052] Because the zonules' or ocular force is limited, it is
desirable to use a fairly thin lens, compared to the full thickness
of the capsular bag. In general, a thin lens may distort more
easily than a very thick one, and may therefore convert the ocular
force more efficiently into a change in power. In other words, for
a relatively thin lens, a lower force is required to cover the full
range of accommodation.
[0053] Note that the lens may be designed so that its relaxed state
is the "far" condition (sometimes referred to as "disaccommodative
biased", the "near" condition ("accommodative biased"), or some
condition in between the two.
[0054] The intraocular lens itself generally has two components, an
optic 21, which is made of a transparent, deformable and/or elastic
material, and a haptic 23, which holds the optic 21 in place and
mechanically transfers forces on the capsular bag 14 to the optic
21. The haptic 23 may have an engagement member with a central
recess that is sized to receive the peripheral edge of the optic
21.
[0055] When the eye 10 focuses on a relatively close object, as
shown in FIG. 1, the zonules 18 relax and compress the capsular bag
14 returns to its natural shape in which it is relatively thick at
its center and has more steeply curved sides. As a result of this
action, the power of the lens increases (i.e., one or both of the
radii of curvature can decrease, and/or the lens can become
thicker, and/or the lens may also move axially), placing the image
of the relatively close object at the retina 16. Note that if the
lens could not accommodate, the image of the relatively close
object would be located behind the retina, and would appear
blurred.
[0056] FIG. 2 shows a portion of an eye 20 that is focused on a
relatively distant object. The cornea 11 and anterior chamber 12
are typically unaffected by accommodation, and are substantially
identical to the corresponding elements in FIG. 1. To focus on the
distant object, the ciliary muscle 37 contracts and the zonules 26
retract and change the shape of the capsular bag 25, which becomes
thinner at its center and has less steeply curved sides. This
reduces the lens power by flattening (i.e., lengthening radii of
curvature and/or thinning) the lens, placing the image of the
relatively distant object at the retina (not shown).
[0057] For both the "near" case of FIG. 1 and the "far" case of
FIG. 2, the intraocular lens itself deforms and changes in response
to the ciliary muscles and/or to the distortion of the capsular
bag. For the "near" object, the haptic 23 compresses the optic 21
at its edge, increasing the thickness of the optic 21 at its center
and more steeply curving its anterior face 19 and/or its posterior
face 22. As a result, the lens power increases. For the "far"
object, the haptic 30 expands, pulling on the optic 28 at its edge,
and thereby decreasing the thickness of the optic 28 at its center
and less steeply curving (e.g., lengthening one or both radius of
curvature) its anterior face 27 and/or its posterior face 29. As a
result, the lens power decreases.
[0058] Note that the specific degrees of change in curvature of the
anterior and posterior faces depend on the nominal curvatures.
Although the optics 21 and 28 are drawn as bi-convex, they may also
be plano-convex, meniscus or other lens shapes. In all of these
cases, the optic is compressed or expanded by forces applied by the
haptic to the edge and/or faces of the optic. In addition, there
may be some axial movement of the optic. In some embodiments, the
haptic is configured to transfer the generally symmetric radial
forces symmetrically to the optic to deform the optic in a
spherically symmetric way. However, in alternate embodiments the
haptic is configured non-uniformly (e.g., having different material
properties, thickness, dimensions, spacing, angles or curvatures),
to allow for non-uniform transfer of forces by the haptic to the
optic. For example, this could be used to combat astigmatism, coma
or other asymmetric aberrations of the eye/lens system. The optic
may optionally have one or more diffractive elements, one or more
multifocal elements, and/or one or more aspheric elements.
[0059] In many cases, it is desirable that during accommodation,
the distortion of the optic produces a change in optic thickness
and/or a change in the radius of curvature of the anterior and/or
posterior surfaces of the optic. Any other types of distortions to
the surface, such as "ripples" or "waves", may unacceptably degrade
the optical performance of the lens. These "ripples" or "waves" are
described in more detail below.
[0060] Because the optic is round, it may be difficult to envision
any undesirable surface ripples that may accompany a squeezing or
expanding of the optic about its equator. For this reason, it is
instructive to consider the geometry of a linear beam or rod, which
can produce analogous ripples along a single dimension. This 1-D
geometry is much simpler to visualize, and adequately describes the
issue of undesirable surface distortion.
[0061] Consider a linear beam or rod, which is being compressed by
pushing on its ends. While the intended effect of the compression
may be to shorten the beam and/or produce a slight bulge along the
length of the beam, an unintended effect may be to cause a small
amount of "buckling" along the length of the beam. Similarly, if
the beam is stretched by pulling on its ends, the intended effect
of the stretching may be to lengthen the beam and/or produce a
slight thinning of the beam along its length, but an unintended
effect may be to cause a small amount of "cracking" along the
surface, similar in character to that of a desert floor. Both the
"buckling" and "cracking" may occur along the surface of the beam,
while the compression or expansion may be initiated at or near the
ends of the beam.
[0062] This analogy may be extended to the two-dimensional,
essentially circular geometry of the accommodating optic. To focus
on relatively near objects, as in FIG. 1, the haptic may squeeze
the optic about its equator and cause a radial compression of the
optic. The intended effect of the squeezing may be to increase the
thickness of the optic and/or change the curvature of the anterior
and/or posterior surfaces of the optic. However, an unintended
effect may be to produce the two-dimensional, circular equivalent
of "buckling" on one or both of these surfaces. Similarly, to focus
on relatively distant objects, as in FIG. 2, the haptic may stretch
the optic about its equator and cause a radial expansion of the
optic. The intended effect of the expansion may be to decrease the
thickness of the optic and/or change the curvature of the anterior
and/or posterior surfaces of the optic. However, an unintended
effect may be to produce the twos dimensional, circular equivalent
of "cracking" on one or both of these surfaces. For the purposes of
this document, the circular equivalents of "buckling" and
"cracking" may be referred to as "ripples" or "waves". For known
optics, these "ripples" or "waves" may degrade the performance of
the optic, which is highly undesirable.
[0063] It is possible that the "ripples" or "waves" during
accommodation may be avoided if the optic has internal stress. For
instance, if the haptic applies a compression or expansion force to
the optic, separate and distinct from any compression or expansion
forces applied by the capsular bag of the eye, then the optic may
have some internal stress, which may reduce any "ripples" or
"waves" that appear during accommodation. The internal stress in
the optic may be present throughout the range of accommodation, or
may alternatively pass through "zero" at some point in the range of
accommodation.
[0064] In some embodiments, the anterior and/or posterior surfaces
may be designed so that they attain particular profiles when the
optic is compressed about its equator, as occurs when the lens is
implanted. For instance, in some embodiments, it may be
particularly desirable to have spherical anterior and/or posterior
surfaces; in these embodiments, the anterior and/or posterior
surface profiles may or may not deviate from spherical when the
optic is uncompressed about its equator. In other words, for some
embodiments, compressing the optic about its equator causes the
anterior and/or posterior surfaces to become more spherical in
profile. If there is asphericity in either surface in the
uncompressed state, it may be reduced when the optic is
compressed.
[0065] FIG. 3 is a flow chart of a manufacturing process 31 that
may induce an internal stress to the optic when the intraocular
lens is in a natual or nominally unstressed state.
[0066] First, externally stress the haptic, as in element 32. In
some embodiments, an external compressive or expansive force is
applied to a haptic, so that the haptic becomes compressed or
stretched. Note that the haptic may be made from a generally
elastic material, so that the haptic may return roughly to its
initial shape and size when the external force is removed.
[0067] Next, place or form an optic within the externally stressed
haptic, as in element 33. In some embodiments, the optic may be
molded or otherwise manufactured directly onto the externally
stressed haptic. In other embodiments, the optic may be
manufactured separately, then attached to the haptic. For the
purposes of this document, for all of these embodiments, the optic
is said to be "placed" within the haptic.
[0068] In some embodiments, the optic is held by the haptic in a
region around the equator of the optic. The haptic may contact the
optic at the edge of the optic, at the circumference of the
anterior face of the optic, and/or at the circumference of the
posterior face of the optic. The haptic may optionally extend over
a portion of the anterior and/or posterior faces, typically around
the edge of the optic and outside the clear aperture of the optic.
In some embodiments, the haptic may not truly surround the optic,
but may contact it in portions at or near the equator of the optic
or may contact it only on the anterior or posterior face. In other
embodiments, portions of the haptic may be disposed inside the
optic so that the haptic portion protrudes into the optic. For the
purposes of this document, the optic is said to be placed "within"
the haptic for all of these orientations.
[0069] Next, remove the external stress from the haptic, as in
element 34. This may involve removing the external compressive or
expansive force applied in element 32.
[0070] The intraocular lens reaches a natural state, as in element
35. For the purposes of this document, a "natural" state is a state
of the intraocular lens in which there is an absence of external
forces, such as external compressive or expansive forces applied in
element 32. In some embodiments, the "natural" state is the state
of the intraocular lens prior to implantation into an eye.
[0071] Finally, the optic is internally stressed, as in element 36.
In some embodiments where the haptic is stiffer than the optic, the
haptic is generally relaxed and returns nearly to the size and
shape it had before the external stress was applied, while the
optic becomes stretched or compressed to maintain contact with the
generally relaxed haptic. Note that in this generally relaxed state
of the intraocular lens, the haptic may have some residual stresses
that oppose the internal stresses of the optic; the magnitude of
these residual stresses may vary inversely with the stiffness of
the haptic. For typical haptics, which are much stiffer than the
optic, the residual stresses are quite small, and the haptic may be
considered to be essentially relaxed.
[0072] For the purposes of this document, an intraocular lens
and/or the optic contained therein in which a haptic uses its
internal stress to affect the internal stress of the optic may be
referred to as a "pre-stressed" intraocular lens and/or a
"pre-stressed" optic.
[0073] FIG. 4 is an end-on drawing of a haptic and optic, shown
throughout various stages of construction. In this figure, the
optical axis is vertical and the plane of the lens is
horizontal.
[0074] For the purposes of this figure and several of the following
figures, the haptic is drawn as being essentially solid, and the
optic is attached to the side of the haptic. It will be understood
that in practice, the haptic may be hollow or cylindrical in
nature, such as a circumferential ring, and may surround all or
part of the optic around its equator and/or may at least partially
protrude into the optic.
[0075] The topmost element 41 is a haptic in a natural, unstressed
state, without an optic.
[0076] The next element down is the haptic 42 with an external
stress applied. An external force, denoted by the shaded arrows at
the left and right of element 42, expands the haptic. The haptic
increases in size, as shown by the dotted lines that indicate the
unstressed size of the haptic. The haptic also has an internal
stress, denoted by the solid arrows inside the haptic. In this
case, the haptic is under tension.
[0077] Still further down, an optic 43 is placed within the
stressed haptic 44. Although the optic typically does not extend
along the optical axis past the edges of the haptic, it is drawn as
such in FIG. 4 for simplicity.
[0078] At the bottom of FIG. 4, the external force is removed from
the haptic 46. The haptic 46 largely relaxes and returns nearly to
its original, unstressed size, as shown by the pair of dotted lines
at each end of the haptic 46. The optic 45, which is mechanically
coupled to the haptic 46 and is typically less stiff than the
haptic 46, provides little resistance to the change in size of the
haptic. As a result, the optic 45 becomes compressed and develops
an internal stress, shown by the pair of solid arrows inside the
optic 45. In this case, the internal stress of the optic 45 is
compression. In other embodiments, the internal stress of the optic
45 is stretched expansion.
[0079] Note that the internal stress of the haptic 46 is largely
relieved by removing the external stress. However, there may be a
small residual internal stress that remains inside the haptic 46,
which is denoted by the thin, solid arrows inside the haptic 46.
The magnitude of this residual stress may be proportional to the
stiffness of the optic 45; if the optic 45 had no stiffness at all,
there would be no residual stress, and the haptic 46 would be
completely relaxed and would return roughly to its unstressed
size.
[0080] FIG. 5 shows the haptic and optic of FIG. 4, only with the
lens in the plane of the page and the optical axis of the lens
being perpendicular to the page.
[0081] Element 41 is the haptic in an unstressed state. For
clarity, the dotted lines showing the unstressed size of the haptic
are omitted.
[0082] Element 42 is the haptic with an external stress applied. In
this case, the external stress is an expansion, and the haptic 42
is under tension. In some embodiments, the external stress and
tension are both radially symmetric.
[0083] Element 43 is the optic, placed within the stressed haptic
44. At this stage, the optic 43 is not under significant
stress.
[0084] The external stress is removed at the bottom of FIG. 5, and
the haptic 46 and optic 45 are both seen to radially contract,
causing an internal stress in the optic 45. In this case, the
internal stress in the optic 45 is compression. At this stage, the
lens may be ready for implantation.
[0085] FIGS. 6 and 7 are analogous to FIGS. 4 and 5, but the
external force applied to the haptic is compression rather than
expansion. Note that combinations of compression and expansion are
possible, with compression along one direction and expansion along
another, although these are not shown in the figures.
[0086] FIG. 6 is an end-on drawing of a haptic and optic, shown
throughout various stages of construction. In this figure, the
optical axis is vertical and the plane of the lens is
horizontal.
[0087] The topmost element 61 is haptic in a natural, unstressed
state, without an optic.
[0088] The next element down is the haptic 62 with an external
stress applied. An external force, denoted by the shaded arrows at
the left and right of element 62, compresses the haptic. The haptic
decreases in size, as shown by the dotted lines that indicate the
unstressed size of the haptic. The haptic also has an internal
stress, denoted by the solid arrows inside the haptic. In this
case, the haptic is under compression.
[0089] Still further down, an optic 63 is placed within the
stressed haptic 64. Although the optic typically does not extend
along the optical axis past the edges of the haptic, it is drawn as
such in FIG. 6 for simplicity.
[0090] At the bottom of FIG. 6, the external force is removed from
the haptic 66. The haptic 66 largely relaxes and returns nearly to
its original, unstressed size, as shown by the pair of dotted lines
at each end of the haptic 66. The optic 65, which is mechanically
coupled to the haptic 66 and is typically less stiff than the
haptic 66, provides little resistance to the change in size of the
haptic. As a result, the optic 65 becomes expanded and develops an
internal stress, shown by the pair of solid arrows inside the optic
65. In this case, the internal stress of the optic 65 is
tension.
[0091] FIG. 7 shows the haptic and optic of FIG, 5, only with the
lens in the plane of the page and the optical axis of the lens
being perpendicular to the page.
[0092] Element 61 is the haptic in an unstressed state. For
clarity, the dotted lines showing the unstressed size of the haptic
are omitted.
[0093] Element 62 is the haptic with an external stress applied. In
this case, the external stress is a compression, and the haptic 62
is under compression. In some embodiments, the external stress and
compression are both radially symmetric.
[0094] Element 63 is the optic, placed within the stressed haptic
64. At this stage, the optic 63 is not under significant
stress.
[0095] The external stress is removed at the bottom of FIG. 7, and
the haptic 66 and optic 65 are both seen to radially expand,
causing an internal stress in the optic 65. In this case, the
internal stress in the optic 65 is tension. At this stage, the lens
may be ready for implantation.
[0096] FIGS. 8 and 9 show a haptic 81 and optic 82 analogous to
those in the bottom portion of FIG. 7, but with an asymmetric
external force applied to the haptic 81. Such an asymmetry may be
used to reduce astigmatism in the optical system of an eye.
[0097] In FIG. 8, a haptic 81 is under compression from an
asymmetric external force. In FIG. 8, the compressive force is
larger in the vertical direction than in the horizontal direction,
although in practice, the asymmetry may have any orientation and
any degree of asymmetry. In addition, the asymmetry may optionally
include a compressive force along one dimension and an expansive
force along another. Alternatively, the asymmetry may include an
expansive force along one dimension and an expansive force with a
different magnitude along a different dimension.
[0098] While under the external compression, the haptic 81 is shown
in FIG. 8 to be elliptical in shape, with a compressed size smaller
than the uncompressed size denoted by the dashed line 83. An optic
82 is placed within the externally compressed haptic 81. At this
stage, the optic 82 is largely unstressed.
[0099] Once the optic is placed within the externally stressed
haptic, the external stress is removed. The haptic 91 and optic 92
then expand, as shown in FIG, 9. The resulting tension within the
optic 92 may be radially asymmetric, with a direction-dependent
tension that varies as a function of how much the haptic 81 was
externally compressed along the particular direction. In FIG. 9,
the tension along the vertical direction is larger than along the
horizontal direction. Note that the asymmetry stresses in the optic
92 may have any orientation, and are not confined to vertical and
horizontal, as shown in FIG. 9.
[0100] Note that in FIGS. 4 though 97 the haptic is stretched or
compressed by an external force. In one embodiment, the external
force is mechanical in origin, and may be realized by pushing or
pulling on various locations on the haptic.
[0101] Note also that for the typical circularly symmetric
geometries of an intraocular lens, the stresses in the haptic and
optic are generally radial in orientation and are generally coaxial
with each other.
[0102] In another embodiment, the pre-stress is caused by shrinkage
or expansion of the materials during molding, extraction or another
manufacturing or processing step. The haptic and the optic may be
made from materials having different mechanical properties, so that
during a shrinking or expanding step, one shrinks or expands more
than the other. If the optic is placed within the haptic before the
shrinking or expanding step, then the optic and/or haptic may
become internally stressed after the shrinking or expanding step.
Note that if the haptic is significantly stiffer than the optic,
then the optic may have significantly more internal stress than the
haptic after the shrinking or expanding step.
[0103] FIG. 10 is a flow chart of an exemplary manufacturing
process 101 that may induce an internal stress to the optic.
Initially, the haptic may be provided for the manufacturing
process. In one embodiment, the haptic is externally stressed,
where the external stress is to be removed at a later manufacturing
step; this is analogous to the manufacturing process shown above in
FIG. 3. In another embodiment, the haptic is essentially unstressed
at this stage. Such an initially unstressed haptic may be made from
a material that may expand or contract in response to a
size-altering process, such as a heating, a cooling, or an
absorption or emission of water or other substance.
[0104] In element 102, an optic is placed within the haptic. In one
embodiment, the optic may be molded onto or around the haptic. In
another embodiment, the optic may be manufactured separately from
the haptic and then attached to the haptic. The optic may be
attached to the interior of the haptic, or may be attached to the
exterior of the haptic. The haptic may surround all or part of the
optic, or may be adjacent to the optic. In all of these cases, the
optic is said to be "placed within" the haptic.
[0105] In element 103, stress is induced between the haptic and the
optic. The stress may be induced by changing the size and/or shape
of the haptic and/or the optic, once the optic has been placed
within the haptic. As long as the haptic and optic expand or
contract by different amounts, there will be a stress between the
haptic and the optic. For instance, the haptic may expand and the
optic may contract, remain the same size, or expand by amount
different from that of the haptic. Alternatively, the haptic may
contract and the optic may expand, remain the same size, or
contract by amount different from that of the haptic. As a further
alternative, the haptic may remain the same size and the optic may
contract or expand.
[0106] Because the haptic and the optic may be connected after
element 102 in FIG. 10, the haptic and optic may not be able to
expand or contract free of each other. For instance, if the haptic
surrounds the optic so that the outer diameter of the optic fits
inside the inner diameter of the haptic, the optic may not expand
significantly compared to what its expansion would be if it were
not mounted within the haptic. In this case, an expansion of the
optic by heating or another method may not produce a significant
expansion of the optic, but may produce compression within the
optic. For this reason, the expansion and/or contraction described
above may be considered to be an expansion and/or contraction in
free space, as if the haptic were detached from the optic.
[0107] In element 104, the haptic and the optic reach a natural
state, analogous to element 35 in FIG. 3. In element 105, the optic
is internally stressed, analogous to element 36 in FIG. 3.
[0108] In one embodiment, the expansion and/or contraction may be
caused by a shrinking and/or expanding step that occurs during
molding, extraction or any other manufacturing or processing step.
For instance, if the haptic has a higher shrinkage than the optic,
and the optic is placed within the haptic before a shrinking step,
then the optic may be in a compressed state after the shrinking
step. Similarly, if the haptic has a lower shrinkage than the
optic, and the optic is placed within the haptic before a shrinking
step, then the optic may be in an expanded state after the
shrinking step.
[0109] In another embodiment, the pre-stress is caused by using
hydrophilic and/or hydrophobic materials for the haptic and/or
optic. Upon insertion into the aqueous solution of the eye, a
hydrophilic material may swell and a hydrophobic material may
shrink or remain the same size. The swelling and/or shrinking upon
insertion into the eye is analogous to the expanding and/or
shrinking steps described above.
[0110] For instance, consider a hydrophilic optic placed within a
hydrophobic haptic. Upon insertion into the aqueous solution of the
eye, the optic may swell and the haptic may absorb some of the
swelling force. The lens may then reach an equilibrium in the eye,
in which the optic may be under compression.
[0111] In one embodiment, the haptic and optic may have different
levels of hydrophilia and/or hydrophobia, so that upon insertion
into the eye they may swell at different rates and may therefore
internally stress the optic.
[0112] As noted in FIGS. 8 and 9, the haptic may be pre-stressed
differently in different directions. In addition, the haptic may
also have an axial component to the pre-stressing. This axial
component may help dampen or eliminate any undesirable axial
movement of the lens during accommodation.
[0113] Because FIGS. 4 though 9 are largely schematic in nature, it
is instructive to consider a haptic having a more realistic
design.
[0114] FIG. 11 is an isometric drawing of an exemplary haptic,
after manufacture and prior to installation in the eye. The optic,
when placed within the haptic, will be located at or near the
center of the haptic. The haptic may protrude into the optic.
Alternatively, the haptic may engage all or a portion of the
periphery of the optic only. The outer circumference of the haptic
mechanically couples with the capsular bag of the eye (not shown),
so that any compression or expansion initiated by the zonules is
coupled into the haptic, and, in turn, into the optic through its
periphery.
[0115] The exemplary haptic has various segments or filaments, each
of which extends generally radially in a plane roughly
perpendicular to the optical axis of the lens. For the exemplary
haptic of FIG. 11 the segments are joined to each other at the
outer circumference and extend radially inward until they contact
the edge of the optic. Alternatively, they need not be joined
together at the outer circumference. At locations other than the
outer circumference, the haptic segments may remain separate from
each other, as shown in FIG. 11, or alternatively some or all
segments may be joined together. Any or all of the width, shape and
thickness of the segments may optionally vary along the length of
the segments. The haptic may have any suitable number of segments,
including but not limited to, 3, 4, 6, 8, 10, 12, 14, and 16.
[0116] The exemplary haptic 110 is then compressed radially, so
that the overall diameter of the haptic is reduced. A typical
compression may be on the order of about 1 mm, although more or
less compression may be used. For instance, the haptic may be
compressed by a fraction of its diameter, such as a value in the
range of about 0.4% to about 2.0%. This compressed state may be
referred to as a "pre-stressed" state.
[0117] FIG. 11 is an isometric drawing of an optic 111 placed
within a haptic 112. The haptic 112 engages a portion of the
periphery of the optic 111 in a region roughly around the equator
115 of the optic 111. This exemplary haptic 112 contacts the optic
111 in four regions, each roughly equally spaced apart around the
equator 115 of the optic 111, although any suitable number of
contact portions may be used and they need not be spaced equally
apart. The haptic 112 includes an annular ring, also known as a
circumferential ring. The ring has an inner diameter given by
element 113, and an outer diameter given by element 114. The ratio
of the inner to out diameters may vary as a function of the
stiffness of the haptic 112. For instance, a stiffer haptic may
require relatively little material, and the ratio may be fairly
close to 1. Alternatively, a less stiff haptic may require more
material, and the ratio may deviate significantly from 1.
[0118] For the haptic shown in FIG. 11, the outer diameter 116 of
the annular ring is the outer portion of the haptic 112, and may
remain in contact with the capsular bag of the eye during and after
implantation. Alternatively, the annular ring may be contained in
the interior of the haptic, with arms or filaments that may extend
outward beyond the outer diameter of the annular ring to contact
the capsular bag; these filaments are analogous to the four
inward-extending filaments shown in FIG. 11. As a further
alternative, the inner diameter of the annular ring may be the
inner diameter of the haptic, and may contact the circumference or
the equator of the optic.
[0119] FIGS. 12 through 18 show an exemplary haptic 120 in various
plan and cross-sectional views, both with and without an optic 130.
FIG. 12 is a cross-section drawing of a haptic 120. FIG. 13 is a
cross-sectional drawing of the haptic of FIG. 12, with an optic
130. FIG. 14 is the cross-section drawing of the haptic 120 and
optic 130 of FIG. 13, with additional hidden lines. FIG. 15 is an
end-on cross-sectional drawing of the haptic 120 and optic 130 of
FIG. 13. FIG. 16 is a plan drawing of the haptic 120 of FIG. 12.
FIG. 17 is a plan drawing of the haptic 120 of FIG. 16, with an
optic 130. FIG. 18 is the cross-section drawing of the haptic 120
and optic 130 of FIG. 17, with additional hidden lines.
[0120] The haptic 120 of FIGS. 12 through 18 has eight filaments
denoted by elements 121a through 121h. Alternatively, the haptic
120 may have more or fewer than eight filaments. The filaments
121a-h may be connected at their outermost edge and may be
unconnected at their innermost edge.
[0121] Note that the filaments 121a-h may vary in size along their
lengths, from the innermost edge 123 to the ends of the filament
adjacent to the outermost edge 122 of the haptic 120. In
particular, the filaments 12la-h may increase in cross-sectional
dimensions with radial distance away from the center of the lens.
In a direction parallel to the optical axis (vertical in FIG. 12),
the outermost extent of the haptic filaments, denoted by length
129, may be larger than the innermost extent of the haptic
filaments, denoted by dimension 128. Alternatively, the length 129
may be equal to or less than length 128. Simlarly, in a direction
perpendicular to the optical axis (essentially in the plane of the
lens), the filaments may be effectively wedge-shaped, with a
greater radial extent at the outer edge than at the inner edge. The
cross-section of each filament may be symmetric with respect to the
plane of the lens, as shown in FIG. 12. Alternatively, the
cross-section of one or more filaments may be asymmetric with
respect to the plane of the lens, with differing amounts of
material on anterior and posterior sides of the filament.
[0122] The outermost edge 122 of the haptic 120 mechanically
couples the intraocular lens to the capsular bag of the eye. The
haptic 120 may receive an optic 130 in its central region, which
may be molded directly onto the haptic 120. Alternatively, the
optic may be manufactured separately from the haptic, then attached
to the haptic.
[0123] The haptic 120 may have an optional lip or ridge 124 on one
or both of the anterior and posterior faces, so that if an optic is
molded directly onto the haptic 120, the optic resides in the
central portion of the haptic within the lip 124. The lip 124 may
be circularly symmetric on both faces of the haptic, as shown in
FIGS. 12 through 18. Alternatively, the lip 124 may have a
different radius on one or more filaments, so that optic material
may extend out different radial distances along particular
filaments. As a further alternative, the lip 124 may have different
radii on the anterior and posterior faces of the haptic 120.
[0124] Once the optic 130 is formed on, attached to, or placed
within the haptic 120, the haptic 120 protrudes into the edge 131
of the optic 130. For the specific design of FIGS. 12 through 18,
portions of each filament 12la-h extend into the edge 131 of the
optic 130, with the anterior and posterior faces of the optic 130
surrounding and/or encompassing the haptic filaments 121a-h in the
central portion demarcated by the lip 124.
[0125] For a cross-section of the filaments 12la-h, taken in a
plane parallel to the optical axis of the lens (vertical in FIGS.
12 through 18), the cross-section has a particular profile that
extends into the edge 131 of the optic 130. The profile may contain
one or more straight and/or curved portions, and may have a deepest
portion at one or more points or along a straight segment. For
instance, the profile in FIGS. 12 and 15 has a generally straight
portion 125 extending generally radially inward, followed by a
generally straight portion 126 extending generally parallel to the
optical axis, followed by a generally straight portion 127
extending generally radially outward. The generally straight
portions 125, 126 and 127 may optionally have one or more rounded
portions 151 between them. Straight portions 125 and 127 may be
generally parallel to each other, or may be generally inclined with
respect to each other. The generally straight portion 126 may be
generally parallel to the optical axis, as in FIGS. 12 and 15, or
may alternatively be inclined with respect to the optical axis. The
deepest portion of the profile of FIGS. 12 and 15 may be the
straight portion 126. The profile made up of segments 125, 126 and
127 shown in FIGS. 12 and 15 may be generally convex in a direction
parallel to the optical axis of the lens. Other configurations of
protruding haptics may incorporated into embodiments of the present
invention such, for examples, those discussed in copending U.S.
patent application Ser. No. 11/618,325, which is herein
incorporated by reference.
[0126] Referring to FIG. 15, the axial thickness (i.e., along an
axis parallel to the optical axis passing through the center of the
optic 130) of the portions of the haptic 120 disposed within the
optic 130 may be selected to control the amount and/or distribution
of an ocular force acting on the intraocular lens 240. For example,
in some embodiments, the performance (e.g., the change Diopter
power of the optic 130 between accommodative and disaccommodative
configurations) increases as the edge thickness increases. In such
embodiments, other design constraints (e.g., optical performance or
physical constraints of the eye) may, however, place an upper limit
on the maximum optic edge thickness. In some embodiments, the
portion of the haptic 120 inside the optic 130 has a maximum axial
thickness that is at least one half a maximum axial thickness of
the optic 130 along the optical axis, as clearly illustrated in
FIG. 15. In other embodiments, the portion of the haptic 120 inside
the optic 130 has a maximum axial thickness that is at least 75% of
a maximum axial thickness of the central zone. The advantages of
the axial thickness the protruding portions of the haptic 120 may
also be applied to other embodiments of the invention discussed
herein.
[0127] In certain embodiments, the optic 130 is a multifocal optic.
For example, the portion of the optic 130 between the ends 126 of
the haptic 120 may comprise a first zone having a first optical
power and the portion of the optic 130 into which the filaments 121
protrude may comprise a second zone having a second optic power
that is different from the first optical power. In some
embodiments, the optic 130 may change from a monofocal optic to a
multifocal optic, depending upon the amount of ocular force on the
haptic 120 and/or the state of accommodation of the eye into which
the intraocular lens is inserted.
[0128] If the optic 130 may be molded directly onto the haptic 120,
the haptic 120 may be first expanded or contracted radially by an
external force, prior to molding. The optic 130 may then be molded
directly onto the expanded or contracted haptic 120. After molding,
the external force may be removed, and the haptic may return to its
original size or fairly close to its original size, forming radial
stresses within the optic 130.
[0129] It is desirable that the haptic be made from a stiffer
material than the optic, so that any distorting forces induced by
the zonules or capsular bag are transmitted efficiently through the
haptic to the optic, and efficiently change the shape of the optic.
It is also desirable that the haptic and the optic have similar or
essentially equal refractive indices, which would reduce any
reflections at the interfaces between the haptic and the optic.
[0130] FIGS. 19 through 21 show another exemplary haptic 190 in
various plan views, both with and without an optic 200. FIG. 19 is
a plan drawing of a haptic 190. FIG. 20 is a plan drawing of the
haptic 190 of FIG. 19, with an optic 200. FIG. 21 is the plan
drawing of the haptic 190 and optic 200 of FIG. 20, with additional
hidden lines.
[0131] The haptic 190 of FIGS. 19 through 21 has eight filaments
denoted by elements 191a through 191h. Alternatively, the haptic
190 may have more or fewer than eight filaments. Filaments 19la-h
may have non-uniformities along their lengths, such as width
variations, height variations, and/or holes 192a-h.
[0132] The holes 192a-h may desirably alter the mechanical
properties of the respective filaments, so that a given zonular
force may be transmitted efficiently into a distortion of the
optic. The holes 192a-h may be triangular in shape, or may be any
other suitable shape, such as round, square, rectangular,
polygonal, and may optionally have one or more rounded corners
and/or edges. Each hole may optionally vary in profile along its
depth. There may optionally be more than one hole per filament.
There may optionally be differing numbers of holes for different
filaments. There may optionally be differently-shaped holes on the
same filament.
[0133] Unlike the filaments 121 a-h of FIGS. 12 through 18, the
filaments 191a-h are connected at both their outermost edge and
their innermost edge. The filaments 19la-h are joined at an outer
annular ring 193 and an inner annular ring 194. The inner annular
ring 194 may lie within the circumference of the optic 200, as in
FIGS. 19 through 21. Alternatively, the inner annular ring 194 may
lie outside the circumference of the optic 200, or may straddle the
circumference of the optic 200.
[0134] The dimensions of the inner annular ring 194, specifically,
the inner and outer diameters of the inner annular ring 194, may be
determined in part by the stiffness of the haptic 190 and/or the
stiffness of the optic 200. For instance, a stiffer haptic may
require relatively little material, and the ratio may be fairly
close to 1. Alternatively, a less stiff haptic may require more
material, and the ratio may deviate significantly from 1.
[0135] FIGS. 22 through 26 show another exemplary haptic 220 in
various plan views, with an optic 230. FIG. 22 is a top-view plan
drawing of a haptic 220 with an optic 230. FIG, 23 is a side-view
plan drawing of the haptic 220 and optic 230 of FIG. 22. FIG. 24 is
a side-view cross-sectional drawing of the haptic 220 and optic 230
of FIG. 22. FIG. 25 is a plan drawing of the haptic 220 and optic
230 of FIG. 22. FIG. 26 is a cross-sectional drawing of the haptic
220 and optic 230 of FIG, 22.
[0136] The haptic 220 of FIGS. 22 through 26 has a more complex
shape than the haptics shown in FIGS. 12 through 21. The haptic 220
has eight filaments 221a-h, each of which has one end attached to
an inner annular ring 222 and has the opposite end attached to an
outer annular ring 223. Alternatively, the haptic 220 may have more
or fewer than eight filaments. In contrast with the haptics of
FIGS. 12 through 21 the haptic 220 contacts the capsular bag of the
eye at one or more points along the filaments 221a-h between the
inner and outer annular rings 222 and 223. In some embodiments, the
filaments 22la-h may loop back on themselves, and may contact the
capsular bag at one or more extrema along the loop, rather than at
the outer annular ring 223.
[0137] As with the inner annular ring 194 of FIGS. 19 through 21,
the inner annular ring 222 may lie inside the circumference of the
optic 230, once the optic 230 is placed within the haptic 220, may
lie outside the circumference of the optic 230, or may straddle the
circumference of the optic 230.
[0138] In some embodiments, such as the disc-shaped intraocular
lenses shown in FIGS. 12 through 21, the haptic filaments engage an
equatorial region of the capsular bag. In many of these
embodiments, the optical power of intraocular lens may be selected
to provide a disaccommodative bias, although some embodiments may
alternatively provide an accommodative bias.
[0139] In other embodiments, the haptic filaments may engage
substantially the entire capsular bag, rather than just the
equatorial region of the capsular bag. In some of these
embodiments, the filaments may extend generally in a plane that
includes the optical axis of the lens, and there may be uncontacted
portions of the capsular bag in the regions between the filaments.
In many of these embodiments, the intraocular lens has an
accommodative bias, although some embodiments may alternatively use
a disaccommodative bias.
[0140] For the designs of FIGS. 12 through 26, the haptic may be
pre-stressed, and the optic may then be molded onto or attached to
the haptic while the haptic is in the pre-stressed state. For
instance, the haptic may be compressed or expanded radially prior
to placing the optic within the haptic. The pre-stress may then be
removed, and the lens may be allowed to relax to its substantially
unstressed state, or a "natural" state. For a haptic that is much
stiffer than the optic, the haptic may expand/contract by nearly
the full compression/expansion amount, and the optic becomes
expanded/compressed about its equator. In its expanded state, the
optic is under radial tension.
[0141] This pre-stress may help reduce or eliminate buckling of the
optic, if the optic is compressed. It may also reduce the need for
a thicker optic for maximizing the power change for a given
external force (e.g., an ocular force produced by the ciliary
muscles, the zonules, and/or the capsular bag of the eye.)
Furthermore, the pre-stress may allow for a so-called "fail-safe"
design that allows only a certain amount of power change during
accommodation; the lens may minimize the power change beyond a
prescribed accommodation range. In addition, the pres-stress may
reduce the amount of force required for a given power change.
[0142] The optic may be made from a relatively soft material, so
that it can distort or change shape readily under the limited
deforming force initiated by the capsular bag and transmitted
through the haptic. An exemplary material is a relatively soft
silicone material, although other suitable materials may be used as
well. The stiffness of the optic 121 may be less than 500 kPa, or
preferably may be between 0.5 kPa and 500 kPa, or more preferably
may be between 25 kPa and 200 kPa, or even more preferably may be
between 25 kPa and 50 kPa.
[0143] In contrast with the optic, the haptic may be made from a
relatively stiff material, so that it can efficiently transmit the
deforming forces from the capsular bag to the optic. An exemplary
material is a relatively stiff silicone material, although other
suitable materials may be used as well, such as acrylic,
polystyrene, or clear polyurethanes. The haptic may preferably be
stiffer than the optic. The stiffness of the haptic may be greater
than 500 kPa, or preferably may be greater than 3000 kPa.
[0144] Because the haptic may extend into the optic in a region
around its circumference, it also may extend into the clear
aperture of the optic. For this reason, the haptic may preferably
be transparent or nearly transparent, so that it does not
substantially block any light transmitted through the lens. The
haptic generally has a power transmission of at least about 80%,
preferably at least 90% or even 95%.
[0145] In addition, it is desirable that the interface between the
optic and the haptic not produce any significant reflections, which
would produce scattered light within the eye, and would appear as a
haze to the patient. A convenient way to reduce the reflections
from the interface is to match the refractive indices of the haptic
and the optic to each other.
[0146] A simple numerical example shows the effect of mismatch of
refractive indices on reflected power. For a planar interface at
normal incidence between air (refractive index of 1) and glass
(refractive index of 1.5), 4% of the incident power is reflected at
the interface. For such an interface between air and glass, there
is no attempt to match refractive indices, and this 4% reflection
will merely provide a baseline for comparison. If, instead of 1 and
1.5, the refractive indices differ by 4%, such as 1.5 and 1.56 or
1.5 and 1.44, there is a 0.04% reflection, or a factor of 100
improvement over air/glass. Finally, if the refractive indices
differ by only 0.3%, such as 1.5 and 1.505 or 1.5 and 1.495, there
is a 0.00028% reflection, or a factor of over 14000 improvement
over air/glass. In practice, tolerances such as the 0.3% case may
be achievable, and it is seen that a negligible fraction of power
may be reflected at the interface between a haptic and an optic
whose refractive indices differ by 0.3%. Note that the above base
value of 1.5 was chosen for simplicity, and that the haptic and
optic may have any suitable refractive index.
[0147] It is desirable that the refractive indices of the haptic
and optic be essentially the same. For the purposes of this
document, "essentially the same" may mean that their refractive
indices are equal to each other at a wavelength within the visible
spectrum (i.e., between 400 nm and 700 nm). Note that the haptic
and optic may optionally have different dispersions, where the
refractive index variation, as a function of wavelength, may be
different for the haptic and the optic. In other words, if the
refractive indices of the haptic and optic are plotted as a
function of wavelength, they may or may not have different slopes,
and if the two curves cross at one or more wavelengths between 400
nm and 700 nm, then the refractive indices may be considered to be
essentially the same or essentially equal.
[0148] The description of the invention and its applications as set
forth herein is illustrative and is not intended to limit the scope
of the invention. Variations and modifications of the embodiments
disclosed herein are possible, and practical alternatives to and
equivalents of the various elements of the embodiments would be
understood to those of ordinary skill in the art upon study of this
patent document. These and other variations and modifications of
the embodiments disclosed herein may be made without departing from
the scope and spirit of the invention.
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