U.S. patent application number 13/362348 was filed with the patent office on 2013-08-01 for accommodating intraocular lens.
The applicant listed for this patent is Andrew F. Phillips. Invention is credited to Andrew F. Phillips.
Application Number | 20130197635 13/362348 |
Document ID | / |
Family ID | 47713839 |
Filed Date | 2013-08-01 |
United States Patent
Application |
20130197635 |
Kind Code |
A1 |
Phillips; Andrew F. |
August 1, 2013 |
Accommodating Intraocular Lens
Abstract
An intraocular lens has a polymeric optic defined by a harder
posterior layer and a softer anterior layer. Haptics having a
fulcrum attached to the posterior layer and a resistance arm
attached to the anterior layer are provided. A bias is provided to
the haptic to rotate the haptics about the fulcrum and cause the
resistance arm to deform the softer anterior layer about the harder
posterior layer to increase the optical power of the lens. As the
haptic rotates, it axially displaces the optic anteriorly to
additionally increase the optical power. The optical power is
adjustable in response to stresses induced by the eye. The haptics
are subject to a pre-bias that urges the haptics to rotate or bend
about the fulcrum. Temporary restraints are provided to the haptics
to retain a stressed shape of the lens against the bias during a
post-implantation healing period.
Inventors: |
Phillips; Andrew F.; (La
Canada, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Phillips; Andrew F. |
La Canada |
CA |
US |
|
|
Family ID: |
47713839 |
Appl. No.: |
13/362348 |
Filed: |
January 31, 2012 |
Current U.S.
Class: |
623/6.37 |
Current CPC
Class: |
A61F 2250/0018 20130101;
A61F 2/1635 20130101; A61F 2/1629 20130101; A61F 2002/1682
20150401 |
Class at
Publication: |
623/6.37 |
International
Class: |
A61F 2/16 20060101
A61F002/16 |
Claims
1. An intraocular lens for replacement of a natural crystalline
lens within a capsular bag during eye surgery, the intraocular lens
to be positioned anterior to the retina when implanted in the eye,
said intraocular lens comprising: a) an optic adapted to focus
light, said optic having an anterior surface, a posterior surface,
and a central portion, said optic comprising, i) a polymeric
posterior first optic layer having a first durometer, an anterior
surface and a posterior surface, said anterior surface having a
peripheral portion with a first radius of curvature and a
relatively steeper central portion, said posterior surface of said
first optic layer defining said posterior surface of said optic,
and ii) a polymeric anterior second optic layer having a second
durometer less than said first durometer, and including a posterior
surface, an anterior surface, and central portion, said posterior
surface of said second optic layer bonded flush against said
anterior surface of said first optic layer, and said anterior
surface of said second optic layer defining said anterior surface
of said optic; b) at least one haptic lever extending from said
optic, each said haptic lever including a fulcrum attached to said
first optic layer, a resistance arm attached to said second optic
layer, and a force arm extending from said optic, wherein when a
force is applied to rotate said haptic lever on said fulcrum in a
posterior direction relative to said second optic layer, i) said
resistance arm pulls said second optic layer to deform said second
optic layer about said central portion of said first optic layer
and steepen a curvature of said anterior surface of said second
optic layer, and ii) said optic is axially displaced anteriorly
relative to said haptic lever; c) biasing means for biasing said
haptic lever to rotate on said fulcrum into a posterior direction
relative to said second optic layer into a non-stressed state; and
d) a restraining element operating against said biasing means so as
to maintain said optic and said at least one haptic lever in a
stressed state of relatively greater planarity than said
non-stressed state, said restraining element being releasable
without an invasive surgical procedure after completion of the eye
surgery during which said intraocular lens is implanted, and when
said lens is implanted in the eye an optical power of said lens is
adjustable in response to stresses induced by the eye.
2. An intraocular lens according to claim 1, wherein: said steeper
central portion of said anterior surface of said first optic layer
has a second radius of curvature smaller than said first radius of
curvature.
3. An intraocular lens according to claim 1, wherein: said first
optic layer is made of a first silicone material, and said second
optic layer is made of a second silicone material.
4. An intraocular lens according to claim 3, wherein: said first
silicone material has a durometer in the range of 30-60 Shore D,
and said second silicone material has a durometer not exceeding 20
Shore D.
5. An intraocular lens according to claim 3, wherein: said at least
one haptic lever is made from a silicone material.
6. An intraocular lens according to claim 5, wherein: said first
optic layer and said at least one haptic lever are made from a same
silicone material.
7. An intraocular lens according to claim 1, wherein: said biasing
means is provided at a junction of said optic and said haptic
lever.
8. An intraocular lens according to claim 1, wherein: said biasing
means is integrated into a periphery of said posterior optic
layer.
9. An intraocular lens according to claim 1, wherein: said biasing
means is a periphery of said posterior optic layer.
10. An intraocular lens according to claim 1, wherein: said
restraining element holds said anterior surface of said optic of
said lens at an first curvature, and when the lens is implanted in
the eye, is released of said restraining element, and is subject to
forces of accommodation, a central portion of said anterior surface
of said optic of said lens assumes a second curvature having a
reduced radius of curvature.
11. An intraocular lens according to claim 1, wherein: said
restraining element holds said optic of said lens in a first shape
having a first diopteric power, and when said lens is implanted in
the eye, is released of said restraining element, and is subject to
forces of accommodation, a central portion of said anterior portion
of said optic of said lens assumes a second shape having a second
diopteric power greater than said first diopteric power.
12. An intraocular lens according to claim 11, wherein said
restraining element extends across said anterior surface of said
optic.
13. An intraocular lens according to claim 1, wherein: said
restraining element is chemically dissolvable.
14. An intraocular lens according to claim 1, wherein: said
restraining element is laser releasable.
15. An intraocular lens according to claim 1, wherein: said at
least one haptic lever comprises two diametrically opposed haptic
levers.
16. An intraocular lens for replacement of a natural crystalline
lens within a capsular bag during eye surgery, the intraocular lens
to be positioned anterior to the retina when implanted in the eye,
said intraocular lens comprising: a) an optic adapted to focus
light, said optic having an anterior surface, a posterior surface,
and a central portion, said optic comprising, i) a polymeric
posterior first optic layer having a first durometer, an anterior
surface and a posterior surface, said anterior surface having a
peripheral portion with a first radius of curvature and a
relatively steeper central portion, said posterior surface of said
first optic layer defining said posterior surface of said optic,
and ii) a polymeric anterior second optic layer having a second
durometer less than said first durometer, and including a posterior
surface, an anterior surface, and central portion, said posterior
surface of said second optic layer bonded flush against said
anterior surface of said first optic layer, and said anterior
surface of said second optic layer defining said anterior surface
of said optic; b) first and second haptic levers each extending
from said optic, said haptic levers each including a fulcrum
attached to said first optic layer, a resistance arm attached to
said second optic layer, and a force arm extending from said optic,
wherein when a force is applied to rotate said haptic lever on said
fulcrum in a posterior direction relative to said second optic
layer, i) said resistance arm pulls said second optic layer to
deform said second optic layer about said central portion of said
first optic layer and steepen a curvature of said anterior surface
of said second optic layer, and ii) said optic is axially displaced
anteriorly relative to said haptic levers; c) biasing means for
biasing said haptic levers to rotate on said respective fulcrums
into a posterior direction relative to said second optic layer to
urge said lens into a non-stressed state; and d) a releasable
restraining element including at least one element extending
continuously across said optic from one of said haptic levers
across said optic to another of said haptic levers, said
restraining element countering said bias between said optic and
said haptic levers so as to maintain said lens in a relatively
planar stressed-state, wherein said restraining element holds said
lens in said stressed state, and when said lens is implanted in the
eye, upon release of said restraining element, said biasing means
(i) urges said optic anteriorly relative to the retina and (ii)
causes rotation of said haptic levers relative to said lens to
deform said central portion of said anterior second optic layer
about said central portion of said anterior surface of said first
optic layer, each resulting in increased optical power of said
lens, and wherein said optical power of said lens is adjustable in
response to stresses induced by the eye.
17. An intraocular lens according to claim 16, wherein: said
biasing means is provided at a junction of said optic and said
haptic levers.
18. An intraocular lens according to claim 16, wherein: said
biasing means is integrated into said posterior optic layer.
19. An intraocular lens according to claim 18, wherein: said
biasing means is integrated into a periphery of said posterior
optic layer.
20. An intraocular lens according to claim 16, wherein: said
biasing means is a periphery of said posterior optic layer.
21. An intraocular lens according to claim 16, wherein: said
restraining element holds said central portion of said anterior
surface of said optic of said lens at a first curvature, and when
said lens is implanted in the eye, is released of said restraining
element, and is subject to forces of accommodation, said central
portion of said anterior surface of said optic lens assumes a
second curvature having a smaller radius of curvature than said
first curvature.
22. An intraocular lens according to claim 16, wherein: said
restraining element holds said optic of said lens in a first shape
in which a central portion of said optic has a first diopteric
power, and when said lens is implanted in the eye, is released of
said restraining element, and is subject to forces of
accommodation, said optic of said lens assumes a second shape in
which said central portion of said lens has a second diopteric
power greater than said first diopteric power.
23. An intraocular lens according to claim 16, wherein said
restraining element extends across said anterior surface of said
optic.
24. An intraocular lens according to claim 16, wherein: said
restraining element is chemically dissolvable.
25. An intraocular lens according to claim 16, wherein: said
restraining element is laser releasable.
26. An intraocular lens according to claim 16, wherein: said
steeper central portion of said anterior surface of said first
optic layer has a second radius of curvature smaller than said
first radius of curvature.
27. An intraocular lens according to claim 16, wherein: said
steeper central portion of said anterior surface of said first
optic layer is defined by a conical section.
28. An intraocular lens according to claim 16, wherein: said first
optic layer is made of a first silicone material, and said second
optic layer is made of a second silicone material.
29. An intraocular lens according to claim 28, wherein: said first
silicone material has a durometer in the range of 30-60 Shore D,
and said second silicone material has a durometer not exceeding 20
Shore D.
30. An intraocular lens according to claim 28, wherein: said first
optic layer and said first and second haptic levers are made from
said first silicone material.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates broadly to ophthalmic implants. More
particularly, this invention relates to intraocular lenses which
are focusable and allow for accommodation for near vision.
[0003] 2. State of the Art
[0004] Referring to FIG. 1, the human eye 10 generally comprises a
cornea 12, an iris 14, a ciliary body (muscle) 16, a capsular bag
18 having an anterior wall 20 and a posterior wall 22, and a
natural crystalline lens 24 contained with the walls of the
capsular bag. The capsular bag 18 is connected to the ciliary body
16 by means of a plurality of zonules 26 which are strands or
fibers. The ciliary body 16 surrounds the capsular bag 18 and lens
24, defining an open space, the diameter of which depends upon the
state (relaxed or contracted) of the ciliary body 16.
[0005] When the ciliary body 16 relaxes, the diameter of the
opening increases, and the zonules 26 are pulled taut and exert a
tensile force on the anterior and posterior walls 20, 22 of the
capsular bag 18, tending to flatten it. As a consequence, the lens
24 is also flattened, thereby undergoing a decrease in focusing
power. This is the condition for normal distance viewing. Thus, the
emmetropic human eye is naturally focused on distant objects.
[0006] Through a process termed accommodation, the human eye can
increase its focusing power and bring into focus objects at near.
Accommodation is enabled by a change in shape of the lens 24. More
particularly, when the ciliary body 16 contracts, the diameter of
the opening is decreased thereby causing a compensatory relaxation
of the zonules 26. This in turn removes or decreases the tension on
the capsular bag 18, and allows the lens 24 to assume a more
rounded or spherical shape. This rounded shape increases the focal
power of the lens such that the lens focuses on objects at
near.
[0007] As such, the process of accommodation is made more efficient
by the interplay between stresses in the ciliary body and the lens.
When the ciliary body relaxes and reduces its internal stress,
there is a compensatory transfer of this stress into the body of
the lens, which is then stretched away from its globular relaxed
state into a more stressed elongated conformation for distance
viewing. The opposite happens as accommodation occurs for near
vision, where the stress is transferred from the elongated lens
into the contracted ciliary body.
[0008] In this sense, referring to FIG. 2, there is conservation of
potential energy (as measured by the stress or level of excitation)
between the ciliary body and the crystalline lens from the point of
complete ciliary body relaxation for distance vision through a
continuum of states leading to full accommodation of the lens.
[0009] As humans age, there is a general loss of ability to
accommodate, termed "presbyopia", which eventually leaves the eye
unable to focus on near objects. In addition, when cataract surgery
is performed and the natural crystalline lens is replaced by an
artificial intraocular lens, there is generally a complete loss of
the ability to accommodate. This occurs because the active muscular
process of accommodation involving the ciliary body is not
translated into a change in focusing power of the implanted
artificial intraocular lens.
[0010] There have been numerous attempts to achieve at least some
useful degree of accommodation with an implanted intraocular lens
which, for various reasons, fall short of being satisfactory. In
U.S. Pat. No. 4,666,446 to Koziol et al., there is shown an
intraocular lens having a complex shape for achieving a bi-focal
result. The lens is held in place within the eye by haptics which
are attached to the ciliary body. However, the implant requires the
patient to wear spectacles for proper functioning. Another device
shown in U.S. Pat. No. 4,994,082 to Richards et al., also utilizes
a lens having regions of different focus, or a pair of compound
lenses, which are held in place by haptics attached to the ciliary
body. In this arrangement, contraction and relaxation of the
ciliary muscle causes the haptics to move the lens or lenses,
thereby altering the effective focal length. There are numerous
other patented arrangements which utilize haptics connected to the
ciliary body, or are otherwise coupled thereto, such as are shown
in U.S. Pat. No. 4,932,966 to Christie et al., U.S. Pat. No.
4,888,012 to Horne et al. and U.S. Pat. No. 4,892,543 to Turley,
and rely upon the ciliary muscle to achieve the desired alteration
in lens focus.
[0011] In any arrangement that is connected to the ciliary body, by
haptic connection or otherwise, extensive erosion, scarring, and
distortion of the ciliary body usually results. Such scarring and
distortion leads to a disruption of the local architecture of the
ciliary body and thus causes failure of the small forces to be
transmitted to the intraocular lens. Thus, for a successful
long-term implant, connection and fixation to the ciliary body is
to be avoided if at all possible.
[0012] In U.S. Pat. No. 4,842,601 to Smith, there is shown an
accommodating intraocular lens that is implanted into and floats
within the capsular bag. The lens comprises front and rear flexible
walls joined at their edges, which bear against the anterior and
posterior inner surfaces of the capsular bag. Thus, when the
zonules exert a tensional pull on the circumference of the capsular
bag, the bag, and hence the intraocular lens, is flattened, thereby
changing the effective power of refraction of the lens. The
implantation procedure requires that the capsular bag be intact and
undamaged and that the lens itself be dimensioned to remain in
place within the bag without attachment thereto. Additionally, the
lens must be assembled within the capsular bag and biasing means
for imparting an initial shape to the lens must be activated within
the capsular bag. Such an implantation is technically quite
difficult and risks damaging the capsular bag, inasmuch as most of
the operations involved take place with tools which invade the bag.
In addition, the Smith arrangement relies upon pressure from the
anterior and posterior walls of the capsular bag to deform the
lens, which requires that the lens be extremely resilient and
deformable. However, the more resilient and soft the lens elements,
the more difficult assembly within the capsular bag becomes.
Furthermore, fibrosis and stiffening of the capsular remnants
following cataract surgery may make this approach problematic.
[0013] U.S. Pat. No. 6,197,059 to Cumming and U.S. Pat. No.
6,231,603 to Lang each disclose an intraocular lens design where
the configuration of a hinged lens support ostensibly allows the
intraocular lens to change axial position in response to
accommodation and thus change effective optical power. U.S. Pat.
No. 6,299,641 to Woods describes another intraocular lens that also
increases effective focusing power as a result of a change in axial
position during accommodation. In each of these intraocular lenses,
a shift in axial position and an increase in distance from the
retina results in a relative increase in focusing power. All lenses
that depend upon a shift in the axial position of the lens to
achieve some degree of accommodation are limited by the amount of
excursion possible during accommodation.
[0014] U.S. Pat. No. 5,607,472 to Thompson describes a dual-lens
design. Prior to implantation, the lens is stressed into a
non-accommodative state with a gel forced into a circumferential
expansion channel about the lens. At implantation, the surgeon must
create a substantially perfectly round capsullorrhexis, and insert
the lens therethrough. A ledge adjacent to the anterior flexible
lens is then bonded 360.degree. around (at the opening of the
capsulorrhexis) by the surgeon to the anterior capsule to secure
the lens in place. This approach has numerous drawbacks, a few of
which follow. First, several aspects of the procedure are
substantially difficult and not within the technical skill level of
many eye surgeons. For example, creation of the desired round
capsullorrhexis within the stated tolerance required is
particularly difficult. Second, the bonding "ledge" may disrupt the
optical image produced by the adjacent optic. Third, intraocular
bonding requires a high degree of skill, and may fail if the
capsullorrhexis is not 360.degree. round. Fourth, the proposed
method invites cautionary speculation as to the result should the
glue fail to hold the lens in position in entirety or over a
sectional region. Fifth, it is well known that after lens
implantation surgery the capsular bag, upon healing, shrinks. Such
shrinking can distort a lens glued to the bag in a pre-shrunk
state, especially since the lens is permanently affixed to a
structure which is not yet in equilibrium. Sixth, Thompson fails to
provide a teaching as to how or when to release the gel from the
expansion channel; i.e., remove the stress from the lens. If the
gel is not removed, the lens will not accommodate. If the gel is
removed during the procedure, the lens is only in a rounded
non-stressed shape during adhesion to the capsule, and it is
believed that the lens will fail to interact with the ciliary body
as required to provide the desired accommodation as the capsular
bag may change shape in the post-operative period. If the gel is
removed after the procedure, it is ostensibly via an additional
invasive surgical procedure. In view of these problems, it is
doubtful that the lens system disclosed by Thompson can be
successfully employed.
[0015] Co-owned U.S. Pat. No. 7,601,169 to Phillips describes an
intraocular lens for placement within the capsular bag. The lens
includes an optic portion and a surrounding peripheral portion. A
bias element is provided to anteriorly vault the optic portion
relative to the peripheral portion. A restraint is provided to
counter the bias element, and constrain the lens in stressed
relatively planar configuration during surgical implantation and a
healing period during which the eye is maintained under cycloplegia
and the peripheral portion and capsular bag are permitted to
naturally fuse together. Then, post-healing, the restraint is
removed permitting the bias element to vault the optic portion
anteriorly into a non-stressed state such that the optic portion is
at an increased distance from the retina relative to the stressed
state and has a resulting increased optical power, and wherein the
optical power of the lens is adjustable in response to stresses
induced by the eye. While significant advantage is provided by the
system, limitations in optical power remain from the system.
[0016] U.S. Pat. No. 8,034,106 to Mentak describes an intraocular
lens retained outside the lens capsule in the posterior chamber.
The lens has haptics coupled to the ciliary body. The optic of the
lens includes an encapsulation of two immiscible liquids in contact
with other and defining a meniscus at their interface.
Alternatively, two miscible liquids are encapsulated and separated
by an optically transparent film at their meniscus. Forces from the
ciliary body are transmitted through the haptics to the interface
of the liquids to alter the curvature of the meniscus, and thus
alter the accommodating power of the lens. While Mentak considers
it an advantage, it may also be considered a drawback that the
Mentak lens uses two liquids within the optic of the lens. Should
the lens leak such liquid, there is serious concern with respect to
the impairment and damage that may be result. In addition, it is
possible that over time the liquids may migrate out of the lens,
causing ocular damage or changing the optical power, or the liquids
may crystallize also leading to vision impairment.
[0017] Thus, the prior art discloses numerous concepts for
accommodating intraocular lenses. However, none are capable of
providing an accommodating implant which does not, in one way or
another, present technical barriers or potential serious
consequences upon failure of the device or provide an system to
which their may be improvement.
SUMMARY OF THE INVENTION
[0018] An intraocular lens (IOL) according to the invention permits
accommodation through two different mechanisms. The IOL includes an
optic and haptic levers. The optic has an anterior surface and a
posterior surface and is defined by a first polymeric optic layer
and a second optic polymeric layer positioned on the first optic
layer. The first polymeric optic layer has a first durometer, an
anterior surface, and a posterior surface that defines the
posterior surface of the optic. The posterior surface of the first
layer has a generally spherical curvature, and the anterior surface
of the first layer has an outer portion with a first spherical
curvature, and a smaller diametered central portion with a steeper
shape, preferably of a second spherical curvature of a lesser
radius of curvature than the first spherical curvature. The second
polymeric optic layer is relatively softer, with a second durometer
lower than the first durometer, an anterior surface with a
generally spherical curvature, and a posterior surface that is
provided flush against anterior surface of the first layer.
[0019] The haptic levers can alter the axial position of the optic
within the posterior chamber and deform the second optic layer,
each operating to change the optical power of the lens. The haptic
levers include a fulcrum attached at the periphery of the first
optic layer, a resistance arm coupled to the anterior surface of
the second optic layer, and a force arm haptic which engages within
the capsular bag. When a force is applied to the haptic levers to
cause relatively posterior bending or rotation of the haptic levers
relative to the optic, the haptic levers are bent or rotated
relative to the first layer, and the following two mechanism are
effected to increase the optical power of the IOL. First, as the
levers rotate about the fulcrums, the resistance arms stretch at
least the anterior surface of the second optic layer. This results
in deformation of the second optic layer as the second optic layer
bends about the smaller diameter central portion on the anterior
surface of the first optic layer to thereby decrease its radius of
curvature (steepen the curvature) and consequently increase the
central optical power of the lens. Second, with the force arms
fixed in the edges of the capsular bag, as the levers bend or
rotate about the fulcrums, the entire optic is axially displaced
anteriorly to increase the optical power of the lens. This state of
increased power permits accommodation.
[0020] For the lens to function optimally in accommodation, the
haptic levers are subject to a pre-bias such that the levers are
naturally biased or otherwise urged to rotate or bend about the
fulcrums to stretch at least the anterior surface of the second
optic layer and to anteriorly displace the optic relative to the
free ends of the force arms. Such pre-bias is preferably applied by
integration of a bias element at the haptic-optic junction. Such
bias element may comprise a resilient polymer hinge and may be
integrated as a periphery of the first optic layer.
[0021] When the IOL is held by the optical system or otherwise with
the haptic levers and optic of the IOL in a more planar
configuration, the force of the bias element must be overcome. The
lens is therefore in a stressed state, but the anterior curvature
of the lens is flatter and of a lower power suitable for
non-accommodative vision.
[0022] A restraining element is preferably provided to the IOL for
temporarily retaining the IOL in a stressed, planar,
non-accommodating configuration during implantation and a
post-operative period. The retraining element may comprise a
dissolvable bioabsorbable material such that the element
automatically releases the optic after a post-operative period, or
may be released under the control of an eye surgeon, preferably via
a non-surgically invasive means such as via a laser or a chemical
agent added to the eye.
[0023] Generally, the method for implanting the intraocular lens
includes (a) inducing cycloplegia; (b) providing the intraocular
lens having an optic portion and haptic levers and having an as
manufactured inherent bias induced between the optic portion and
haptic levers, the intraocular lens being held in a stressed,
planar, non-accommodating state by a restraining means such that
the intraocular lens has a lower optical power relative to an
accommodating non-stressed state of the lens; (c) inserting the
stressed state intraocular lens into a capsular bag of the eye; (d)
maintaining cycloplegia until the capsular bag physiologically
affixes to the intraocular lens; and (e) releasing the restraining
means to permit the intraocular lens to move from the stressed
state into the non-stressed state in which the intraocular lens has
an increased optical power, and wherein the optical power of the
intraocular lens is reversibly adjustable in response to stresses
induced by the eye such that the lens can accommodate.
[0024] More particularly, according to a preferred method of
implantation, the ciliary body muscle is pharmacologically induced
into a relaxed stated (cycloplegia), a capsulorrhexis is performed
on the lens capsule, and the natural lens is removed from the
capsule. The prosthetic lens is then placed within the lens
capsule. According to a preferred aspect of the invention, the
ciliary body is maintained in the relaxed state for the duration of
the time required for the capsule to naturally heal and shrink
about the lens; i.e., possibly for several weeks. After healing has
occurred, the restraining element automatically or under surgeon
control releases the lens from the stressed state. The ciliary body
and lens may then interact in a manner substantially similar to the
physiological interaction between the ciliary body and a healthy
natural crystalline lens.
[0025] Alternatively, a fully relaxed lens (i.e., without
restraining element) can be coupled to a fully stressed and
contracted ciliary body.
[0026] The intraocular lens of the invention is compatible with
modern cataract surgery techniques and allows for large increases
in optical power of the implanted lens. Unlike other proposed
accommodating intraocular lens systems, the lens utilizes a change
in shape in addition to axial displacement of the lens. In
addition, given the fully polymerized materials of the lens, it is
safe to use, eliminating various factors from the prior art that
can lead to tissue irritation and damage and vision impairment.
[0027] Additional objects and advantages of the invention will
become apparent to those skilled in the art upon reference to the
detailed description taken in conjunction with the provided
figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Prior Art FIG. 1 is a diagrammatic view of a cross-section
of a normal eye.
[0029] Prior Art FIG. 2 is a graph of the stresses on the ciliary
body-crystalline lens system of the eye in a continuum of states
between distance vision and full accommodation.
[0030] FIG. 3 is a schematic view of an intraocular lens according
to the invention in a non-stressed, accommodating
configuration.
[0031] FIGS. 4-6 illustrate manufacture of the intraocular lens of
FIG. 3 into a restrained, stressed configuration suitable for
implantation.
[0032] FIG. 7 shows the intraocular lens implanted in a lens
capsule of an eye in a stressed, non-accommodative state.
[0033] FIG. 8 shows the intraocular lens implanted in a lens
capsule of an eye in a non-stressed, accommodative state.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0034] Turning now to FIG. 3, an intraocular lens (IOL) 100
according to the invention is shown. The IOL 100 includes an optic
102 for focusing light and one or more haptic levers 104. The optic
102 has an overall diameter preferably approximately 4.+-.2 mm, and
most preferably 4.75 mm. The optic 102 is defined by a posterior
first polymeric optic layer 106 and an anterior second optic
polymeric layer 108 positioned on the first optic layer. The
posterior first optic layer 106 defines a posterior surface of the
optic, and the anterior second optic layer 108 defines an anterior
surface of the optic. The first polymeric optic layer 106 is
manufactured from a fully-polymerized optically transparent
material, preferably a silicone, and has a first durometer
preferably in the range of 30 to 60 Shore D. The first optic layer
has a posterior surface 110 and an anterior surface 112. The
posterior surface 110 of the first optic layer has a generally
spherical curvature, and the anterior surface 112 of the first
optic layer has a peripheral portion 114 approximating the overall
optic diameter and having a first spherical curvature, and a
smaller diameter steeper central portion 116, approximately 3.+-.1
mm, preferably having a second spherical curvature of lesser radius
of curvature than the first spherical curvature. Alternatively, the
steeper central portion may be defined by a cone or a conical or
frustoconical section. As yet another alternative, the steeper
central portion may be defined by another shape, including an
aspherical curve, a square edge, or a catenary. The second optic
layer 108 has a posterior surface 120 that is bonded flush against
the anterior surface 112 of the first optic layer 106 and an
anterior surface 122 with a generally spherical curvature. The
second optic layer 108 is made from a fully-polymerized optically
transparent material, preferably a silicone, with a second
durometer lower than the first durometer and preferably not
exceeding 20 Shore D. The second optic layer preferably has a
maximum thickness of 80-750 .mu..
[0035] As discussed in more detail below, when the lens 100 is
implanted in the capsular bag, forces from the ciliary body of the
eye act through the capsular bag and on the one or more haptic
levers 104 to (1) alter the axial position of the optic 102 within
the posterior chamber of the eye and (2) alter the shape of the
second optic layer 108, each of which operates to change the
optical power of the lens 100. The haptic levers 104 are stated to
be `one or more` as such may comprise a single ring-shaped lever
completely or substantially encircling the periphery of the optic
100, or may comprise a plurality of haptic levers in a preferably
evenly radially spaced apart distribution about the periphery of
the optic. In the illustrated embodiment, two haptic levers 104 are
shown in diametric opposition. However, where a plurality of haptic
levers are provided, it is appreciated that two, three, four or
more haptic levers can be preferably evenly displaced about the
periphery of the optic.
[0036] The haptic levers 104 include a fulcrum 130 attached at a
peripheral portion 128 (either at one or both of the anterior or
posterior surfaces thereof or at the junction of the anterior and
posterior surfaces) of the first optic layer 106, a resistance arm
132 coupled to the periphery of the anterior surface 122 of the
second optic layer 108, and a force arm 134 having a free 136 end
which is adapted to engage the capsular bag near the ciliary body.
The haptic levers 104 are also made from a polymer, and more
preferably from the same polymer with same hardness/softness as the
first optic layer 106. The resistance arms 132 are preferably
200-500 .mu. in length, and the force arms 134 are preferably 2.75
mm in length.
[0037] When a force is applied to the haptic levers 104 to cause
relatively posterior rotation of the haptic levers relative to the
optic 102 (in the direction of arrows 138), the haptic levers 104
are rotated relative to the first optic layer 106, and the
following two mechanism are effected to increase the optical power
of the lens. First, as the haptic levers 104 rotate on the fulcrums
130, the resistance arms 132 stretch at least the anterior surface
122 of the second optic layer 108. This results in deformation of
the second optic layer 108 as the second optic layer bends about
the smaller diameter central portion 116 on the anterior surface of
the first optic layer 106 to thereby decrease its radius of
curvature and consequently increase the optical power of the lens
100. Second, with the force arms 134 fixed in the edges of the
capsular bag, as the levers 104 rotate about their respective
fulcrums 130, the entire optic 102 is axially displaced anteriorly
(in the direction of arrow 140) within the posterior chamber to
increase the optical power of the lens. This state of increased
power permits accommodation.
[0038] For the lens to function optimally in accommodation, the
haptic levers are preferably subject to a pre-bias such that the
levers are naturally urged to rotate or bend about the fulcrum into
an approximately 40.degree..+-.10.degree. angular bend relative to
the diameter of the optic to thereby stretch at least the anterior
surface of the second optic layer and to anteriorly displace the
optic relative to the free ends of the force arms. Such pre-bias is
preferably applied by a bias structure 142 at the haptic-optic
junction, and may comprise a resilient polymer hinge 142a
integrated at the periphery of the first optic layer 106 or may
include a separate bias element 142b acting between the posterior
first optic layer 106 and the haptic levers 104.
[0039] Referring to FIGS. 4 through 6, construction of the optic is
preferably as follows. Referring initially to FIG. 4, the posterior
first optic layer 106 is molded, preferably with the haptic levers
104 integrated via the molding process. In the first step of the
molding process, the fulcrums 130 of the haptic levers 104 are
molded into the first optic layer 106 at the periphery 114 of the
first optic layer, and the haptic levers 104 are oriented angled
posteriorly to the first optic layer to cause the first optic layer
106 to be in a `vaulted` configuration relative to the force arms
134 of the haptic levers. In an alternative manufacture, the first
optic layer 106 and the haptic levers 130 may be integrated at a
lesser angle or even in a relatively flat configuration, and a
separate bias element 142b is thereafter provided at the
haptic-optic junction to bias the construct into the `vaulted`
configuration. Turning now to FIG. 5, once the first optic layer
106 is integrated with the haptic levers 130, the first optic layer
106 and haptic levers 130 are held in a substantially planarized
configuration; i.e., with the force arms 134 extending
substantially parallel (preferably within .+-.5.degree.) with the
diameter D of the first optic layer 106, and the second optic layer
is molded onto the anterior surface of the first optic layer and
with the periphery of the second optic layer 108 coupling to the
resistance arms 132 of the haptic levers 130.
[0040] Referring now to FIG. 6, once the second optic layer 108 has
at least substantially cured on the first optic layer 106, a
temporary restraint is provided to the optic to maintain the
planarized non-accommodative configuration for purposes of
implantation and a for a period of post-implantation. Several types
of temporary restraints may be used. In one example, the temporary
restraint is a suture 146 extending from a first haptic lever 130
across the anterior surface of the second optic layer 108 to a
second haptic lever 130. The suture may extend through and be
secured at a small hole 148 in the respective haptic levers. The
suture is sufficiently taught to maintain the planarized
configuration. Alternative restraints includes rigid struts
attached to the hatpic levers and extending across the front or
back of the optic to maintain the planarized configuration. Yet
other alternative restraints include hinge stops at the
optic-haptic junction that maintain the planarized configuration by
preventing rotation of the haptic levers relative to the optic.
Each of the restraints may be made of a dissolvable bioabsorbable
material such that the restraint automatically releases the lens
from the planarized configuration after a determined post-operative
period, or may be released under the control of a eye surgeon,
preferably via a non-surgically invasive means such as via a laser
or a chemical agent added to the eye.
[0041] The lens is implanted in the eye as follows. The patient is
prepared for cataract surgery in the usual way, including full
cycloplegia (paralysis of the ciliary body). Cycloplegia is
preferably pharmacologically induced, e.g., through the use of
short-acting anticholinergics such as tropicamide or longer-lasting
anticholinergics such as atropine. An anterior capsullorrhexis is
then performed and the lens material removed. A stressed planarized
lens according is selected that has an optic portion that in a
stressed-state has a lens power that will leave the patient
approximately emmetropic after surgery. The lens is inserted into
the empty capsular bag. Cycloplegia is maintained for several weeks
(preferably two to four weeks) or long enough to allow the capsular
bag to heal and "shrink-wrap" around the stressed lens. This can be
accomplished post-operatively through the use of one percent
atropine drops twice daily. As the capsular bag shrinks, the
anterior and posterior capsular bag walls join to the lens. If the
lens includes a restraining element having a dissolvable component,
eventually the dissolvable material is lost from the lens, and the
lens is unrestrained. If the lens includes a restraining element
having a laser-removable component, a surgeon may at a desired time
remove the component to place the lens in a unrestrained
configuration. If the lens includes a retraining element which must
be otherwise removed from the patient, either via a non-surgically
invasive procedure or a surgically invasive procedure, the surgeon
may at a desired time perform a second eye procedure to remove the
component and place the lens in an unrestrained configuration.
Regardless of the method used, when the lens is unrestrained (i.e.,
released from the stressed state) as shown in FIG. 7, and the
post-operative cycloplegic medicines are stopped, the lens 100 is
initially still maintained in a stressed state due to the inherent
stress of the zonules in the non-accommodating eye. When the
patient begins accommodating, the zonular stress is reduced and the
implanted lens is permitted to reach a more relaxed configuration,
as shown in FIG. 8. With release of the zonular stress, the haptics
levers 130 reconfigure the lens in accord with the inherent bias of
the lens; i.e., to rotate approximately 40.degree..+-.10.degree.
relative to the diameter D of the posterior optic layer 106 causing
(1) deformation of the anterior optic layer 108 about the central
portion 116 of the posterior optic layer 106 to a cause the
anterior optic layer to assume a steeper curvature of greater
optical power at the center thereof and (2) anterior axial
displacement of the optic 102 relative to the free ends 136 of the
haptic levers 130. Theses changes in shape provide the lens with
greater dioptic power in the central portion of the optic 102, and
thus accommodation for the patient is enabled. As with the natural
crystalline lens, the relaxation of the implanted lens, i.e., its
permitted movement in accord with its inherent bias, is coupled
with a development of strain or stress in the ciliary body during
accommodation. Further, when the patient relaxes accommodation, the
stress in the ciliary body is reduced, and there is a compensatory
gain in stress as the lens is stretched into its planar,
non-accommodative shape shown in FIG. 7.
[0042] In another embodiment of the implantation of a lens
according the invention, a lens of similar design as described
above is used except that there is no restraining element on the
lens. Temporary cycloplegia is induced, and a capsulorrhexis is
performed. The lens is implanted while the ciliary body is in a
fully relaxed state. The patient is then fully accommodated (i.e.,
the ciliary body is placed in a contracted state), preferably
through pharmacological agents such as pilocarpine. Once the
capsular bag is fully annealed (affixed) to the lens periphery, the
pharmacological agent promoting accommodation is stopped. Then, as
the ciliary body relaxes, the lens is stretched into an elongated
shape having less focusing power. Conversely, as accommodation
recurs, the lens returns to it resting shape having greater
focusing power.
[0043] Alternatively, a fully relaxed lens (i.e., without
restraining element) can be coupled to a fully stressed and
contracted ciliary body.
[0044] The intraocular lens systems described above operates to
provide accommodation through a change in shape in and position of
the optic resulting from an equilibrium of the anatomical forces
and the forces in the lens.
[0045] The intraocular lens of the invention is compatible with
modern cataract surgery techniques and allows for large increases
in optical power of the implanted lens. Unlike other proposed
accommodating intraocular lens systems, the lens utilizes a change
in shape in addition to axial displacement of the lens. In
addition, the fully polymerized silicone materials of the lens are
safe to use, eliminating various factors from the prior art,
including potential tissue irritation, damage and vision
impairment, and significant hurdles from regulatory
authorities.
[0046] There have been described and illustrated herein embodiments
of an intraocular lens. While particular embodiments of the
invention have been described, it is not intended that the
invention be limited thereto, as it is intended that the invention
be as broad in scope as the art will allow and that the
specification be read likewise. Thus, while silicone is the
preferred material for all components of the lens, it is
appreciated that other polymers, such as acrylics can also be used.
In addition, particularly where other materials are used, a
different range of durometers for each of the first and second
optic layers can be used. It will therefore be appreciated by those
skilled in the art that yet other modifications could be made to
the provided invention without deviating from its spirit and scope
as claimed.
* * * * *