U.S. patent application number 12/785255 was filed with the patent office on 2010-12-16 for ophthalmic lenses with enhanced surface and methods of fabrication thereof.
This patent application is currently assigned to Abbott Medical Optics Inc.. Invention is credited to Daniel G. Brady, Timothy R. Bumbalough.
Application Number | 20100318186 12/785255 |
Document ID | / |
Family ID | 42668074 |
Filed Date | 2010-12-16 |
United States Patent
Application |
20100318186 |
Kind Code |
A1 |
Bumbalough; Timothy R. ; et
al. |
December 16, 2010 |
OPHTHALMIC LENSES WITH ENHANCED SURFACE AND METHODS OF FABRICATION
THEREOF
Abstract
An ophthalmic lens for providing enhanced vision includes a
finished optic comprising a base optic and a membrane. The base
optic has an anterior surface and an opposing posterior surface, at
least one of the surfaces having a first value of a surface quality
parameter. The base optic also includes a membrane including an
inner surface and an outer surface, the inner surface covering one
or more of the surfaces of the base optic. The outer surface has a
second value of the surface quality parameter, wherein the second
value is greater than the first value.
Inventors: |
Bumbalough; Timothy R.;
(Fullerton, CA) ; Brady; Daniel G.; (San Juan
Capistrano, CA) |
Correspondence
Address: |
ABBOTT MEDICAL OPTICS, INC.
1700 E. ST. ANDREW PLACE
SANTA ANA
CA
92705
US
|
Assignee: |
Abbott Medical Optics Inc.
Santa Ana
CA
|
Family ID: |
42668074 |
Appl. No.: |
12/785255 |
Filed: |
May 21, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61180822 |
May 22, 2009 |
|
|
|
Current U.S.
Class: |
623/6.43 ;
351/159.73 |
Current CPC
Class: |
A61F 2250/0053 20130101;
A61F 2/1613 20130101; A61F 2/1637 20130101; B29D 11/023 20130101;
A61F 2002/1699 20150401; A61F 2/1616 20130101; A61F 2/1618
20130101; A61F 2/1648 20130101; A61F 2/1654 20130101; A61F 2240/001
20130101; A61F 2210/0076 20130101; A61F 2/164 20150401; A61F
2002/1681 20130101 |
Class at
Publication: |
623/6.43 ;
351/177 |
International
Class: |
A61F 2/16 20060101
A61F002/16; G02C 7/02 20060101 G02C007/02 |
Claims
1. A method of making an intraocular lens, comprising: forming a
support structure; forming a base optic having an anterior surface
and an opposing posterior surface; and processing the base optic to
change a physical characteristic of the base optic; and subsequent
to processing the base optic, forming a finished optic by affixing
a membrane to at least one of the surfaces of the base optic.
2. The method of claim 1, further comprising processing the
finished optic.
3. The method of claim 2, wherein processing the base optic and
processing the finished optic comprises extracting impurities from
the intraocular lens.
4. The method of claim 3, wherein extracting impurities comprises
performing a Soxhlet extraction.
5. The method of claim 1, further comprising affixing a first
membrane to the anterior surface of the base optic and a second
membrane to the posterior surface of the base optic.
6. The method of claim 1, wherein forming the base optic includes
forming the base optic about a protruding portion of the support
structure.
7. An intraocular lens, comprising: a finished optic comprising: a
base optic having an anterior surface and an opposing posterior
surface, at least one of the surfaces having a first value of a
surface quality parameter; and a membrane including an inner
surface and an outer surface, the inner surface covering one or
more of the surfaces of the base optic, the outer surface having an
a second value of the surface quality parameter, the second value
being greater than the first value; and a support structure coupled
to the finished optic.
8. The intraocular lens of claim 7, wherein the base optic and the
membrane are integrally formed.
9. The intraocular lens of claim 7, wherein the base optic and the
membrane are made from the same material.
10. The intraocular lens of claim 7, wherein the base optic is made
from a first material having a first value of a property and the
membrane is made from a second material having a second value of
the property, the first value being greater than or less than the
second value.
11. The intraocular lens of claim 10, wherein the property is one
or more of stiffness, tensile strength, modulus, lubricity, or
tackiness
12. The intraocular lens of claim 10, wherein the values differ by
at least 2%.
13. The intraocular lens of claim 10, wherein the values differ by
at least 5%.
14. The intraocular lens of claim 7, wherein the quality parameter
is selected from the group consisting of surface smoothness,
surface accuracy, and modulation transfer function.
15. The intraocular lens of claim 7, wherein the support structure
comprises one or more haptics.
16. The intraocular lens of claim 7, wherein the support structure
includes a protruding portion disposed between the surfaces of the
base optic, wherein the base optic has a first refractive index at
a wavelength within the visible spectrum and the protruding portion
has a second refractive index at the wavelength, the first
refractive index being about equal to the second refractive
index.
17. The intraocular lens of claim 7, wherein the support structure
includes a protruding portion disposed between the surfaces of the
base optic, wherein the base optic has a first refractive index at
a wavelength within the visible spectrum and the protruding portion
has a second refractive index at the wavelength, the first
refractive index being unequal to the second refractive index.
18. The intraocular lens of claim 7, wherein the base optic has a
first refractive index at a wavelength within the visible spectrum
and the membrane has a second refractive index at the wavelength,
the first refractive index being about equal to the second
refractive index.
19. The intraocular lens of claim 7, wherein the base optic has a
first refractive index at a wavelength within the visible spectrum,
the membrane has a second refractive index at the wavelength, the
protruding portion has a third refractive index at the wavelength,
the refractive indices being about equal to one another.
20. The intraocular lens of claim 7, wherein the base optic and the
membrane is made of a common polymeric material.
21. The intraocular lens of claim 7, wherein the membrane is made
of a different material than the base optic.
22. The intraocular lens of claim 21, wherein the base optic has a
first refractive index at a wavelength within the visible spectrum
and the membrane has a second refractive index at the wavelength,
the first refractive index being about equal to the second
refractive index.
23. The intraocular lens of claim 21, wherein the base optic has a
first refractive index at a wavelength within the visible spectrum
and the membrane has a second refractive index at the wavelength,
the first refractive index being unequal to the second refractive
index.
24. The intraocular lens of claim 7, wherein the base optic
comprises a peripheral edge joining the anterior surface of the
base optic to the posterior surface of the base optic.
25. The intraocular lens of claim 24, wherein the finished optic
comprises a wall portion disposed over at least a portion of the
peripheral edge of the base optic.
26. The intraocular lens of claim 24, wherein the finished optic
comprises a first membrane disposed over the anterior surface of
the base optic and a second membrane disposed over the posterior
surface of the base optic, the wall portion joining the first
membrane and the second membrane along circumferential portions of
the membranes.
27. The intraocular lens of claim 7, wherein the membrane has a
thickness that is less than or equal to 0.15 millimeters.
28. The intraocular lens of claim 7, wherein the membrane has a
thickness that is less than or equal to 10% of an axial thickness
of the finished optic along the optical axis.
29. The intraocular lens of claim 7, wherein the support structure
includes a protruding portion disposed along a line parallel to the
optical axis within a peripheral portion of the finished optic.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional
Application No. 61/180,822, filed on May 22, 2009, the entire
disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to ophthalmic lenses
and methods of making ophthalmic lenses, more specifically to
ophthalmic lenses formed with enhanced outer surfaces.
[0004] 2. Description of the Related Art
[0005] Intraocular lenses (IOLs) are used to replace or supplement
the natural lens of an eye. Accommodative intraocular lenses
(AIOLs) may be used to provide a range of optical powers or optic
positions that at least partially restore the ability to focus on
objects over a range of distances. AIOLs are typically more
difficult to produce due to increased performance demands compared
to more traditional monofocal or multifocal intraocular lenses.
[0006] For example, an AIOL may include a more complex support
structure than the relatively simple haptics of more traditional
monofocal or multifocal IOLs, which have relatively simple design
requirements--for example to keep an optic centered and stable
within an eye of a subject. By contrast, the structures for
supporting the optic of an AIOL may be required to precisely move
an optic and/or to change the shape of the optic. In order to
provide a reasonable range of accommodation, AIOL supporting
structures must also be able to efficiently transfer relatively
small amounts of ocular forces to provide the maximum amount of
optic movement and/or shape change. In addition, optic materials
for AIOLs may be required to be relatively soft in order to enhance
the ability of the optic to change shape. By contrast, the
associated support structure material may be required to be much
stiffer to facilitate transfer of ocular forces. These differences
in material properties between the optic and support structure can
make construction of a unitary IOL difficult. As a result of all of
these requirements, it has been found that it is generally more
difficult to fabricate an AIOL that has the same high optical
performance common with more traditional monofocal or multifocal
IOLs.
[0007] Accordingly, other methods of producing intraocular lenses
in general, and accommodating intraocular lenses more specifically,
are needed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Embodiments of the present invention may be better
understood from the following detailed description when read in
conjunction with the accompanying drawings. Such embodiments, which
are for illustrative purposes only, depict novel and non-obvious
aspects of the present invention. The drawings include the
following figures:
[0009] FIG. 1 is a top view of an intraocular lens according to an
embodiment of the present invention.
[0010] FIG. 2 is a top view of a support structure of the
intraocular lens shown in FIG. 1 prior to attachment of an
associated optic portion.
[0011] FIG. 3 is a side view of the intraocular lens shown in FIG.
1.
[0012] FIG. 4 is a block diagram of a method of making an
ophthalmic lens according to an embodiment of the present
invention.
[0013] FIG. 5 is a side view of the support structure and a base
optic of the intraocular lens shown in FIG. 1.
[0014] FIG. 6 is a side view of the support structure and a base
optic of the intraocular lens shown in FIG. 5 after further
processing.
[0015] FIG. 7 is a side view of a mold for fabricating the
intraocular lens shown in FIG. 1.
DETAILED DESCRIPTION OF THE DRAWINGS
[0016] The present invention is generally directed to lenses and
methods of making and using such lenses, that provide enhanced
optical performance in ophthalmic applications, for example, where
complex lens support structures make optical requirements more
difficult to attain. Embodiments of the present invention may find
particular use in the field of accommodative optics, where
relatively complex design requirements make it more difficult to
produce optics delivering both high quality optical performance and
a required amount of accommodative change. While the present
description below is generally directed to accommodating
intraocular lenses (AIOLs), embodiments of the present invention
may include other types of lenses or optics, for example, other
types of ophthalmic lenses such as monofocal or multifocal
intraocular lenses, toric lenses, optically optimized lenses,
contact lenses, corneal implants, and the like.
[0017] Embodiments of the present invention are directed to
intraocular lenses that meet high optical performance requirements,
even where complex support structures and/or difficult material
challenges have traditionally made this more difficult. In the area
of AIOLs, it has been found that when a soft optic material is
molded around a pre-existing optic positioning device or support
structure made of a different material, differences in shrinkage
rates may cause deformation of optic surfaces that can compromise
optical performance. The amount of unwanted optic deformation may
be amplified even more when the optic/support structure combination
is further processed to extract unwanted contaminants from the
intraocular lens. Accordingly, AIOLs according to embodiments of
the present invention are able to overcome such challenges.
[0018] In certain embodiments, it has been discovered that the
optical quality of an optic may be restored after molding and/or
extraction of contaminants by forming a thin membrane or film over
one or both optical surfaces of a base optic. In this manner, the
shape and surface quality of the membrane surfaces are made
superior to original surfaces of the base optic. By carefully
configuring the membrane with a small thickness or volume, any
subsequent shrinkage is rendered negligible, resulting in an optic
that has superior optical performance compared to the originally
molded base optic.
[0019] In some embodiments, the application of a membrane or film
to a base optic, can enhance performance in other ways besides
simply improving the optical quality of the optic surface. Examples
of such enhanced performance include, but are not limited to,
provision of a multifocal optic surface (either refractive or
diffractive) from a monofocal base optic, provision of an aspheric
optic from a spherical base optic, or provision of chromatic
correcting optic (e.g., by application of a diffractive profile to
a base optic or by formation of a secondary optic from a material
having a different refractive index and/or Abbe number than that of
the base optic). Additionally or alternatively, the membrane or
film may be made of a different material, or have different
material properties, than the underlying base optic. For example,
all or portions of the membrane or film may have a different
stiffness, tensile strength, modulus, lubricity, tackiness than the
base optic, and/or optical properties such as transmission or UV
cut-off.
[0020] Referring to FIGS. 1-3, an intraocular lens 100 according to
an embodiment of the present invention comprises a finished optic
105 and a support structure or positioning device 110. The finished
optic 105 is disposed about an optical axis OA and includes a base
optic 115 having an anterior surface 120 and an opposing posterior
surface 125. The finished optic 105 is formed when a layer or shell
135 is applied or attached to base optic 115. Beneficially,
intraocular lens 100 may be configured to be an accommodating
intraocular lens in which a relatively finished optic 105 changes
shape in response to an ocular force.
[0021] The shell 135 comprises an anterior membrane or film 140
with an outer surface 145 that covers anterior surface 120 of base
optic 115. The shell 135 further comprises a posterior membrane or
film 150 with an outer surface 155 covering posterior surface 125
of base optic 115. Membranes 140, 150 also include inner surfaces
that contact, and generally conform to, anterior and posterior
surfaces 120, 125, respectively, of base optic 115. The inner
surfaces of membranes 140, 150 may adhere to surfaces 120, 125 in
such a way that there is no, or little, air or other material
between the membrane inner surfaces and surfaces 120, 125 of the
base optic 115. In certain embodiments, finished optic 105 includes
only one of the membranes 140, 150. As used herein, the term
"membrane" means a sheet or layer of a material that has a maximum
linear extent (i.e. diameter) that is much greater than the maximum
thickness of the layer of material. In this context, the term "much
greater" means the layer of material has a maximum extent that is
at least 10 times greater than the maximum thickness. In some
embodiments, the membrane may have a maximum extent that is at
least 20 times, 50 times, or 100 times greater than the maximum
thickness of the layer of material.
[0022] Base optic 115 may further comprise a clear aperture 160 and
a peripheral edge or wall 165 that joins or connects anterior and
posterior surfaces 120, 125 of base optic 115. As used herein, the
term "clear aperture" means the opening of a lens or optic that
restricts the extent of a bundle of rays from a collimated source
or a distant light source that can be imaged or focused by the lens
or optic. The clear aperture is usually circular and specified by
its diameter. Thus, the clear aperture represents the full extent
of the lens or optic that is usable in forming an image or for
focusing light from a distant point source. In some embodiments,
the clear aperture has the same or substantially the same diameter
as the optic. Alternatively, the diameter of the clear aperture may
be smaller than the diameter of the optic, for example, due to the
presence of a glare or PCO reducing structure disposed about a
peripheral region of the optic.
[0023] Shell 135 may additionally comprise a peripheral edge cover
170 that covers peripheral edge 165. Peripheral edge cover 170
circumferentially extends along peripheral edge 165 and extends
between or joins anterior membrane 140 and posterior membrane 150
of finished optic 105. Peripheral edge cover 170 may have a
thickness (i.e., in a radial direction from the optical axis OA)
that is equal to, or approximately equal to, a thickness of either
or both membranes 140, 150. Alternatively, peripheral cover 170 may
have a thickness that is greater than a thickness of either or both
membranes 140, 150, for example, 50% greater than the thickness of
membranes 140, 150, or 100% greater than the thickness of membranes
140, 150.
[0024] In the illustrated embodiment, support structure 110
optionally includes protruding portions 180 that are disposed
within base optic 115. Protruding portions 180 may be configured to
allow ocular forces produced by the ciliary muscle and/or capsular
bag of an eye to be more effectively transferred to central
portions of finished optic 105, thereby increasing the
accommodative ranges of intraocular lens 100. Such designs are
discussed in greater detail in U.S. Patent Application Numbers
2008-0161913 and 2008-0161914, both of which are herein
incorporated by reference in their entirety.
[0025] Base optic 115 and membranes 140, 150 may generally be made
of any of the various materials known in the art including, but not
limited to, silicone polymeric materials, acrylic polymeric
materials, hydrogel-forming polymeric materials (e.g.,
polyhydroxyethylmethacrylate, polyphosphazenes, polyurethanes,
polystyrene, and mixtures thereof), and the like. Other
formulations of silicone, acrylic, or mixtures thereof are also
anticipated. Selection parameters for suitable lens materials are
well known to those of skill in the art. See, for example, David J.
Apple, et al., Intraocular Lenses: Evolution, Design,
Complications, and Pathology, (1989) William & Wilkins, which
is herein incorporated by reference in its entirety. Support
structure 110 may be constructed of more rigid materials including,
but not limited to, polymeric materials such as silicone polymeric
materials, acrylic polymeric materials, low water content
hydrophilic, hydrogel-forming polymeric materials, polypropylene,
polymethylmethacrylate PMMA, polycarbonates, polyamides,
polyimides, polyacrylates, 2-hydroxymethylmethacrylate, poly
(vinylidene fluoride), polytetrafluoroethylene, polystyrene, and
the like.
[0026] In an embodiment, membranes 140, 150 may be made of a
material that has a similar or the same modulus as the base optic
115. In an embodiment, membranes 140, 150 may be made of a material
that has a higher modulus than the base optic 115 and/or of a
material with lower extractables than base optic 115. Using a
material having a higher modulus and/or lower extractables for
membranes 140, 150 may result in less shrinkage of the material
during fabrication. Less or minimal shrinkage of membranes 140, 150
may result in an improved surface and optical quality of finished
optic 105, which is described further herein.
[0027] Foldable/deformable materials are particularly advantageous
since lenses made from such deformable materials may be rolled,
folded or otherwise deformed and inserted into the eye through a
small incision. Lens materials may have a refractive index allowing
a relatively thin and flexible optic section, for example, having a
thickness in the range of about 150 microns to about 3000 microns.
Finished optic may have a diameter from 4 mm or less to 7 mm or
more, generally from about 5.0 mm to about 6.0 mm. Base optic 115
and/or membranes include 140, 150 may also include more advanced
formulations, for example to provide material properties desirable
in AIOLs. Examples of suitable materials are disclosed in U.S.
Patent Application Publication Number 2009/0088839 and in
co-pending U.S. patent application Ser. Nos. 11/963,351 (U.S.
Publication No. 2009/0163602) and 12/205,703 (U.S. Publication No.
2009/0164009)--all these disclosures being incorporated by
reference in their entirety.
[0028] In some embodiments, the surface and/or optical quality of
outer surfaces 145, 155 of membranes 140, 150 may be generally
higher than the surface or optical quality of surfaces 120, 125 of
base optic 115. For example, outer surface 145 of anterior membrane
140 may be generally smoother than anterior surface 120 of base
optic 115, while outer surface 155 of posterior membrane 150 may be
generally smoother than posterior surface 120 of base optic 115.
Moreover, the optical quality of outer surface 145 of anterior
membrane 140 may be higher than the optical quality of anterior
surface 120 of base optic 115, while the optical quality of outer
surface 155 of posterior membrane 150 may be higher than the
optical quality of posterior surface 120 of base optic 115.
[0029] The refractive index of films 140, 150 and/or protruding
portions 180 may be equal to, or about equal to, the refractive
index of base optic 115. As used herein, the refractive index of
two materials are equal to one if they have the same refractive
index at one or more wavelengths within the visible spectrum (i.e.,
a wavelength from 400 nm to 700 nm). As used herein, the refractive
indices of two materials are "about equal" to one another if their
refractive indices are within 0.4% at one or more wavelengths
within the visible spectrum, preferably within 0.1% at one or more
wavelengths within the visible spectrum. By matching the refractive
indices, the amount of reflections between surfaces may be
significantly reduced. In such embodiments, the Abbe number of
films 140, 150 and/or protruding portions 180 may also be equal to,
or about equal to, the Abbe number of base optic 115. As used
herein, the Abbe numbers of two materials are "about equal" to one
another if their Abbe numbers are within 2.0 of one another,
preferably within 0.5 of one another. In an embodiment, matching
support structure 110 to base optic 115 is tighter or closer than
matching films 140, 150 to base optic 115. In other words, there is
less difference in refractive indices or Abbe numbers between
support structure 110 to base optic 115 than between films 140, 150
to base optic 115.
[0030] In some embodiments, the refractive index and/or the Abbe
number of membranes 140, 150 are different from the refractive
index and/or Abbe number of base optic 115. For example, a
difference in refractive index and/or the Abbe number may be
utilized to reduce chromatic aberrations of finished optic 105. In
such embodiments, one or both films 140, 150 may be replaced by a
second optic that is relatively thick and configured, in
combination with base optic 115, to reduce a chromatic aberration
or achromatic aberration of the intraocular lens 100 itself or of
an eye into which intraocular lens 100 is placed. In an embodiment,
the UV cut-off of films 140, 150 are different from the base optic
115. In an embodiment, the percent transmission across the visible
spectrum should be substantially equivalent between support
structure 110 and films 140, 150.
[0031] In some embodiments, one or both films 140, 150 may define a
plurality of echelettes of a diffractive grating. The diffractive
grating may be a monofocal diffractive grating, for example
configured to reduce a chromatic aberration of finished optic 105
and/or of an eye into which intraocular lens 100 is placed.
Alternatively, the diffractive grating may be a multifocal
diffractive grating, for example configured to provide both distant
vision and near vision, to provide both distant and intermediate
vision, or to provide an extended depth of focus. In certain
embodiments, one of the outer surfaces 145, 155 has a diffractive
grating, while the opposite surface 155, 145 is part of a second
optic as describe above for reducing a chromatic or achromatic
aberration.
[0032] In certain embodiment, all or portions of shell 135 may be
made of the same material as base optic as base optic 115. This may
be a useful configuration for matching the refractive indices
and/or Abbe numbers between base optic 115 any or all of membrane
140, membrane 150, and/or peripheral edge cover 170. Alternatively,
any or all of membrane 140, membrane 150, and/or peripheral edge
cover 170 may be made of a different material than the material
used to form base optic 115 or of the same material that is
processed in a different manner to provide a different physical,
mechanical, or optical property. For example, any or all of
membrane 140, membrane 150, and/or peripheral edge cover 170 may be
made of a material having a different stiffness, tensile strength,
modulus, lubricity, and/or tackiness than base optic 115. As
another example, either or both of membranes 140, 150 may be made
of a material having a different refractive index and/or Abbe
number, for example, to provide a refractive achromat finished
optic 105. In some embodiments, base optic 115 is made from a first
material having a first value of a property and one or more of
elements 140, 150, 170 are made from a second material having a
second value of the property, wherein the first value is greater
than the second value. The difference in the first and second
values may be greater than 2%, greater than 5%, greater than 10%,
or even greater than 25%.
[0033] Where applicable, in any or all of the embodiments of the
previous paragraph, rather than using a material that is different
from base optic 115, the same material, or a common polymeric
material, may be used with any or all of membrane 140, membrane
150, and/or peripheral edge cover 170. In such embodiments, the
material of elements 140, 150, and/or 170 may be processed in a
different way than the material of base optic 115 to provide a
different physical, mechanical, or optical property. Alternatively,
the material of elements 140, 150, and/or 170 may be made of a
common polymeric material to that of base optic 115. As used
herein, a "common polymeric material" refers to similarity of
material composition between two objects or portions of an object,
wherein the two objects or portions consist essentially of the same
base polymer chain or have at least 50% w/w of the same base
polymer chain, or 75% w/w of the same base polymer chain, or 85%
w/w of the same base polymer chain, or 90% w/w of the same base
polymer chain, or 95% w/w of the same base polymer chain, and, when
present, the same cross-linking agent.
[0034] Any or all of elements 140, 150, and/or 170 may be affixed
or joined to base optic 115. In some embodiments, an adhesive
material is disposed between base optic 115 and any or all of
elements 140, 150, and/or 170, for example, to join, glue, or
couple any or all of elements 140, 150, and/or 170 to base optic
115. In some embodiments, base optic 115 and any or all of elements
140, 150, and/or 170 form a unitary or one-piece structure.
[0035] Referring to FIG. 4, a method 200 of making an intraocular
lens comprises an element 210 of forming a positioning device or
support structure of an intraocular lens and an element 220 of
forming a base optic of the intraocular lens. Method 200 further
comprises an element 230 of processing the base optic and an
element 240 of subsequently forming a finished optic. The method
200 also comprises an element 250 of further processing the
finished optic. In certain embodiments, one or more of the elements
of the method 200 are left out (e.g., element 230 and/or element
250). In certain embodiments, a tumbling step may be added to
method 200 after element 210, 220, 230, 240, and/or 250, e.g.
tumbling support structure 110 to remove flash before molding base
optic 115.
[0036] In an embodiment, the radius of curvature of films 140, 150
may be substantially equivalent to the surface shape of base optic
115. Alternatively, due to the processing in element 240, a
spherical shape difference between films 140, 150 and base optic
115 may result in an aspheric surface to improve performance.
[0037] With additional reference to FIGS. 5-7, an exemplary
embodiment of the use of method 200 for fabricating the intraocular
lens 100 will be discussed. Referring again to FIG. 2, fabrication
of intraocular lens 100 begins with element 210 of method 200,
comprising forming support structure 110. Support structure 110 may
be formed using a molding process, for example an automated
injection molding process or a compression molding process, in
which material for support structure 110 may be manually injected
into a mold. Alternatively, support structure 110 may be milled or
machined. In such embodiments, the entire support structure 110 may
be machined from a blank. Alternatively, support structure 110 may
initially be molded and then at least portions of the molded
structure machined, for example to provide features that require
more precise tolerancing. In certain embodiments, support structure
110 may be further processed after molding and/or machining,
although such processing may be done later in the method 200, for
example after base optic 115 has been attached or added.
[0038] Referring to FIG. 5, fabrication of intraocular lens 100
next includes element 220 of method 200, comprising forming base
optic 115. Base optic 115 may be formed using injection or
compressing molding, for example similar to that used to form
support structure 110 in element 210. However, in this case support
structure 110 is disposed inside the mold so that base optic 115 is
formed around support structure 110.
[0039] Base optic 115 may be formed of the same material as support
structure 110, for example so that both parts form a unitary
structure with no detectable boundary between elements 110, 115
and/or to reduce potential for glare at interfaces between
materials of dissimilar refractive index. In certain embodiment,
base optic 115 is made of a material that is softer, or has a lower
modulus or tensile strength, than support structure 110. Such an
arrangement is beneficial where intraocular lens 100 is an
accommodating intraocular lens in which finished optic 105 changes
shape, optical power, and/or axial position in response to an
ocular force in order to provide accommodation. Such difference in
material or optical properties may be provided by making support
structure 110 and base optic 115 from different materials.
Alternatively, support structure 110 and base optic 115 may be made
from a common polymeric material, but support structure 110 is
hardened more than base optic 115, for example by different
exposures to a hardening process and/or by adding different
concentrations of a hardening or catalytic agent. In certain
embodiments, this may be accomplished by using different hydride to
vinyl ratios and/or different amounts of a cross-linking agent for
each element 110, 115, as discussed in greater detail in U.S.
Patent Application Publication Number 2009/0088839, which is hereby
incorporated by reference in its entirety.
[0040] Fabrication of intraocular lens 100 next includes element
230 of method 200, comprising processing base optic 115 and/or
support structure 110. For example, parts 110, 115 may go through
an extraction process, such as a Soxhlet extraction process, for
removing unwanted impurities. Referring to FIG. 6, an unwanted
consequence of the molding and/or extraction processes is that
elements 110, 115 may experience uneven shrinkage rates. Uneven
shrinkage can affect the surface quality of optical surfaces 120,
125 of base optic 115, resulting in a loss of the optical quality
and performance. This may be particularly pronounced near
interfaces between base optic 115 and support structure 110.
[0041] The surface quality of optical surfaces 120, 125 may be
evaluated according to any of the methods used within the art, for
example as disclose in various standards such as Mil-O-13830A,
Mil-PRF-13830B, ISO 4287, or the like. The surface quality may be
expressed in terms of an RMS roughness, where a lower RMS roughness
corresponds to higher surface quality. Surface quality may also be
expressed in terms of deviations from a desired profile or shape.
The surface quality may then be expressed with an average or
standard deviation from the desired profile, with a lower deviation
corresponding to higher surface quality. In some embodiments, the
desired surface shape of surface 120 and/or surface 125 is a sphere
having a predetermined radius of curvature. Alternatively, at least
one of the surfaces 120, 125 has a surface profile expressed by an
equation for a defining a conoid of rotation, wherein a surface sag
profile varies according to the relation:
cr 2 1 + 1 - ( 1 + k ) c 2 r 2 ##EQU00001##
where c is a base curvature of the surface portion (which is equal
to 1/R, where R is the radius of curvature, k is a conic constant,
and r is the radial distance from the optical axis OA.
Alternatively, at least one of the surfaces 120, 125 has a surface
profile expressed by an equation defining a modified conoid of
rotation, wherein a surface sag profile varies according to the
relation:
cr 2 1 + 1 - ( 1 + k ) c 2 r 2 + a 4 r 4 + a 6 r 6 + ...
##EQU00002##
where a.sub.2, a.sub.4, . . . are constants, c is a base curvature
of the surface portion (which is equal to 1/R, where R is the
radius of curvature, k is a conic constant, and r is the radial
distance from the optical axis OA.
[0042] One or more of various metrics may be used in directly
expressing, determining, or evaluating the optical quality of base
optic 115, finished optic 105, and/or any or all of surfaces 120,
125, 145, 155. For example, the optical quality may be expressed in
terms of a Modulation Transfer Function (MTF) performance under
certain conditions at one or more spatial frequencies. In some
embodiments the MTF value is evaluated at spatial frequencies of
25, 50, or 100 line pairs per mm, for example when base optic 115
or finished optic 105 is evaluated in an eye model including an
average cornea. Typical MTF values may include 0.05, 0.10, 0.15,
0.17, 0.20, 0.25, 0.40, 0.55 or higher. Such eye models include,
but are not limited to, the Navarro eye model (as published in the
journal Optical Sciences of America, Vol. 2, No. 8, pp 1273-1281)
or eye model disclosed in TABLE 12, and the associated description,
in U.S. Pat. No. 6,609,793 (herein referred to as the "ACE Eye
Model"), both of which are incorporated by reference in their
entirety.
[0043] Other metrics known in the art for expressing, determining,
or evaluating the optical quality of optics 105, 115 and/or
surfaces 120, 125, 145, 155 include, but are not limited to, MTF
volume (integrated over a particular range of spatial frequencies,
either in one dimension or in two dimensions), resolution, diopter
power, astigmatism, Strehl ratio, encircled energy, RMS spot size,
peak-to-valley spot size, RMS wavefront error, peak-to-valley
wavefront error, edge transition width, interferometry, wavefront
analysis, and resolution by group-element. Additionally or
alternatively, any of the following psychophysical metrics may be
used: contrast sensitivity, visual acuity, and perceived blur. In
addition, other metrics may be found in the literature, such as
those detailed in Marsack, J. D., Thibos, L. N. and Applegate, R.
A., 2004, "Metrics of optical quality derived from wave aberrations
predict visual performance," J Vis, 4 (4), 322-8; Villegas, E. A.,
Gonzalez, C., Bourdoncle, B., Bonnin, T. and Artal, P., 2002,
"Correlation between optical and psychophysical parameters as a
function of defocus," Optom Vis Sci, 79 (1), 60-7; van Meeteren,
A., "Calculations on the optical transfer function of the human eye
for white light," Optica Acta, 21 (5), 395-412 (1974), all of these
references being herein incorporated by reference in their
entirety. Any or all of the above metrics may be evaluated at a
single wavelength, such as 550 nm or any other suitable wavelength,
at a plurality of selected wavelengths, or over a spectral region,
such as the visible spectrum from 400 nm to 700 nm. The metrics may
be weighted over a particular spectral region, such as the
weighting associated with the spectral response of the human eye.
It will be appreciated that the above criteria may be used in
determining or comparing the performance of any of the optic or
optic surfaces discussed herein.
[0044] Fabrication of intraocular lens 100 also includes element
240 of method 200, comprising fabricating finished optic 105.
Referring to FIG. 7, a mold 300 is shown that may be used for
fabricating finished optic 100. Mold 300 includes upper and lower
portions 310, 315 that join together at parting interface 320.
Portions 310, 315 together form a cavity 325 configured to receive
support structure 110 and base optic 115. Elements 110, 115 and
cavity 325 are shown in FIG. 7 by dashed lines. Mold 300 includes a
fixture 330 and associated access port 335 for injecting material
into an inner cavity of mold 300. Mold 300 also includes a fixture
340 and associated port 345 for venting overflow material from the
inner cavity of mold 300. Finished optic 105 may be formed by
compression molding or injection molding.
[0045] Mold 300 may be the same mold used to form the base optic
115, or at least have the same, or approximately the same, cavity
dimensions as cavity 325 of mold 300. Alternatively, mold 300 may
be different from the mold used to form base optic 115 and/or
cavity 325 may have different dimensions in the area of the optic
than the cavity used to form base optic 115. In some embodiments,
different cavity sizes and/or surface profiles are used in forming
base optic 115 and finished optic 105, for example, to provide a
predetermined thickness of membrane 140 or to provide a final
surface profile that is different that that of base optic 115
(e.g., to provide a diffractive surface, multifocal surface, and/or
an aspheric surface configured to reduce spherical
aberrations).
[0046] In some embodiments, the central thickness of the mold used
to form base optic 115 is thicker than the central thickness of
mold 300 used to form final optic 105. In such embodiments, the
central thickness of base optic 115 shrinks after molding, for
example as the result of an extraction process to remove
impurities. Thus, the central thickness of processed base optic 115
is less than the central thickness of cavity 325 or final optic
105. In this way, the thickness of membrane 140 is less than it
would be if the same mold 300 and/or mold cavity 325 were used to
form both base optic 115 and final optic 105. In another
embodiment, the central thickness of the mold used to form base
optic 115 is thinner than the central thickness of mold 300 used to
form final optic 105. Such an embodiment may be used to form a
membrane 140 thickness that is greater than would result if the
same mold 300 and/or mold cavity 325 were used to form both base
optic 115 and final optic 105.
[0047] Fabrication of finished optic 105 may be used to correct
deviations in the surface profile and/or optical performance of
surfaces 120, 125 of base optic 115. Additionally or alternatively,
fabrication of finished optic 105 may serve other purposes. Such
purposes include modification or enhancement of the shape or
profile of at least one of the surfaces 120, 125. For example,
element 240 of method 200 may include altering or modifying
surfaces 120 and/or 125 to provide an aspheric shape or profile for
correcting a monochromatic aberration of lens 100 and/or an
aberration of an eye into which intraocular lens 100 is placed. The
resulting outer surface 145 and/or 155 may be configured to correct
a monochromatic aberration such as a spherical aberration, an
astigmatism, coma, trefoil, or the like. Additionally element 240
of method 200 may include altering surfaces 120 and/or 125 to
provide a refractive multifocal profile, altering surfaces 120
and/or 125 to provide a monofocal or multifocal diffractive profile
(e.g. to correct a chromatic aberration, produce multiple foci,
and/or provide an extended depth of focus), or the like.
[0048] In certain embodiments, method 200 is used to produce a
shell 135 that include both anterior and posterior membranes 140,
150. Alternatively, method 200 may be used to provide only anterior
membrane 140 or only posterior membrane 150. For example, the
anterior surface of finished optic may contain only anterior
membrane 140, while posterior surface 125 is of sufficient quality
that posterior membrane 150 is unnecessary. Alternatively, one of
the surfaces of finished optic 105 may comprise a surface of a
second optic, as discussed in greater detail above.
[0049] Fabrication of finished optic 105 results in membranes or
films 140 and 150 that are relatively thin. Generally, the
thickness of membranes 140, 150 are each less than or equal to
about 0.2 mm or less than or equal to 15% of the total center
thickness of finished optic 105, preferably less than or equal to
10% of the total center thickness of finished optic 105. For
example, in one embodiment, the center thickness of finished optic
105 is about 2.0 millimeters and the thickness of each film 140,
150 is 0.15 mm, or about 7.5% of the center optic thickness. As
used herein, the term "about", when used in the context of a linear
measurement in millimeters, means within .+-.0.1 mm if the
measurement is given to the first decimal point and within .+-.0.01
mm if the measurement is given to the second decimal point. In an
embodiment, the center thickness of finished optic 105 is less than
or equal to 2.5 mm.
[0050] Fabrication of intraocular lens 100 may optionally include
element 250 of method 200, comprising processing finished optic
105. For example, processing of finished optic 105 may include an
additional extraction process to remove contaminants from membranes
140, 150. In such embodiments, the relatively thin membrane reduces
or eliminates the amount of shrinkage of the membranes 140, 150
that occurs during extraction. Accordingly, the thickness of the
membrane after processing is generally less than 0.25 mm,
preferably less than 0.20 mm, and even more preferably less than or
equal to 0.15 mm or even 0.10 mm. A lower limit on the thickness of
membranes 140, 150 exists that depends on such considerations as
the amount of variation or RMS roughness of surfaces 120, 125 of
base optic 115, as well as on practical fabrication considerations
such as how thin a layer may be injected into a mold used to form
finished optic 105. In an embodiment, the thickness of membranes
140, 150 may vary around base optic 115 depending upon the shape
and surface features of base optic 115 yielding portions or
sections of membranes 140, 150 that have a thickness greater than
0.25 mm, but the average thickness of the entire membrane 140, 150
is less than or equal to 0.25 mm. For example, base optic 115 may
have an undulating (wavy) surface where a portion of membrane 140,
150 is thicker than 0.25 mm, but the average thickness over the
entire extent of membrane 140, 150 is less than or equal to 0.25
mm.
[0051] Method 200 may include additional elements. For example,
element 240 and/or element 250 may be repeated. For example, once
an optic is formed in element 240 to provide membranes 140 and/or
150, intraocular lens 100 may again be placed inside mold 300, or a
different mold, to increase the thickness, smoothness, or optical
quality of membranes 140, 150 and finished optic 105. Between
placements into mold 300, or another mold, the newly formed optic
may be processed according to element 250 or otherwise processed.
Element 240 of method 200 may be repeated with one or more molds as
many times as necessary to provide a desired surface
characteristic, optical characteristic, and/or optical quality. In
some embodiments, the entirety, or at least the majority, of either
or both outer surfaces 145, 155 may be formed using this repeated
molding procedure. Alternatively, only selected portions of either
or both outer surfaces 145, 155 may be formed using this repeated
molding procedure, for example, to produce a different optical
characteristic or optical quality of a central portion of finished
optic 105 as compared to a peripheral portion of finished optic
105.
[0052] For the illustrated embodiment shown in FIG. 3, the
thickness or average thickness of membranes 140, 150 is constant,
or approximately constant (e.g., due to surface variations or RMS
roughness of surfaces 120, 125 of base optic 115), with radius from
optical axis OA. In certain embodiments, the thickness or average
thickness of membrane 140 and/or membrane 150 varies with radius
from optical axis OA. For example, the thickness at the center or
optical axis OA of the finished optic 105 is thicker that at the
periphery of finished optic 105. Such thickness variation may
advantageously aid the final molding process to form finished optic
105 and/or result in an overall or average membrane thickness that
is thinner than if a uniform membrane thickness were used.
[0053] Experimental results have shown that the method 200 can be
used to provide an intraocular lens, such as the intraocular lens
100, that has an optical quality that is significantly better than
an intraocular lens that is substantially the same, but made
without a membrane or film, such as the film 140. For example, it
has been found that when intraocular lens 100 is made according to
all of the elements of method 200, the resulting finished optic 105
may have an MTF value (at a spatial frequency of 50 line pairs per
mm and an aperture of 5 mm) that is at least twice that of a
reference intraocular lens made of the same material and/or mold
(e.g., mold 300), wherein the reference intraocular lens is made
using only elements 210-230 of method 200 (e.g., to produce the
base optic 115 shown in FIG. 6). Generally, the MTF value (at a
spatial frequency of 50 line pairs per mm and an aperture of 5 mm)
of finished optic 105 is at least 10% higher than a that of a
reference intraocular lens made of the same material and/or mold
(e.g., mold 300) and using only elements 210-230 of method 200, the
reference intraocular lens having the same optical power, or the
same optical power to within .+-.2 Diopters, as finished optic 105.
Preferably, the MTF value (at a spatial frequency of 50 line pairs
per mm and an aperture of 5 mm) of finished optic 105 is at least
25% higher, 50% higher, 100% higher, or even 200% higher than that
of such a reference intraocular lens.
[0054] The above presents a description of the best mode
contemplated of carrying out the present invention, and of the
manner and process of making and using it, in such full, clear,
concise, and exact terms as to enable any person skilled in the art
to which it pertains to make and use this invention. This invention
is, however, susceptible to modifications and alternate
constructions from that discussed above which are fully equivalent.
Consequently, it is not the intention to limit this invention to
the particular embodiments disclosed. On the contrary, the
intention is to cover modifications and alternate constructions
coming within the spirit and scope of the invention as generally
expressed by the following claims, which particularly point out and
distinctly claim the subject matter of the invention.
* * * * *