Note: Descriptions are shown in the official language in which they were submitted.
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INTRAOCULAR LENSES MADE FROM
POLYMERIC COMPOSITIONS
Background of the Invention
The present invention relates to ophthalmic lenses
made from polymeric compositions. More particularly, the
invention relates to ophthalmic lenses, preferably
deformable intraocular lenses, having reduced surface
tackiness made from acrylate and/or methacrylate-based
polymeric compositions.
Intraocular lenses (IOLs) have been known for a long
time, since shortly after the end of World War II. Such a
lens is surgically implanted into a mammalian eye, e.g.,
human eye, to replace a damaged or diseased natural lens of
the eye and restore the patient's vision.
Although IOLs are made from "hard" or "rigid"
polymeric or glass optical materials, such as polymethyl
methacrylate (which has a refractive index of 1.49), soft
resilient polymeric materials, such as silicones, have been
increasingly used, for the reasons discussed below, in
ophthalmic applications.
Since soft IOLs are deformable, for example, foldable
or rollable, for implantation, a smaller incision can be
surgically cut in the eye than for the implantation of
"hard" IOLs of the same optical power. The smaller the
incision, the less trauma the patient's eye experiences and
the faster post-operative healing occurs. An incision of
about 3 mm is ideal since this size incision is presently
required to remove the natural lens after it has been
broken up, for example, emulsified in a conventional
phaceoemulsification procedure. In contrast the typical
IOL optic has a diameter of about 6 mm.
The size and mechanical characteristics of the
deformable IOLs play an important role. As is well
understood by those skilled in the art, for successful
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implantation, the deformable IOL must have sufficient
structural integrity, elasticity and elongation and be
small enough in size to permit deforming for insertion
through a small incision. After insertion, the lens must,
of course, regain its original shape and have sufficient
structural integrity to retain such shape under normal use
conditions.
In general, the thinner the deformable IOL the small.er
the incision in the eye that is required. On the other
hand, in order to function optically as an IOL, the lens
must have sufficient optical refractory power. Also, the
higher the optical refractive index of the material making
up the IOL, the thinner the IOL can be and still obtain the
same optical refractory power.
Deformable IOLs made of acrylic materials can be quite
tacky in nature, which tackiness inhibits deforming to a
sufficiently small size for insertion through a very small
incision and/or may cause handling problems
Gupta U.S. Patent 4,834,750 discloses IOLs with optics
made of copolymers of methacrylate esters which form
homopolymers that are relatively hard at room temperature
and acrylate esters which form homopolymers that are
relatively soft at room temperature. Such copolymers are
cross-linked with a diacrylate ester to produce an acrylate
material which preferably includes a constituent derived
from a fluoroacrylate to reduce surface tackiness. None of
the specific monomers disclosed in this patent provide
homopolymers which have a refractive index of at least
about 1.50.
Weinschenk, III U.S. Patent 5,331,073 discloses
acrylic-based intraocular lenses which optionally include
a constituent derived from a hydrophilic monomeric
component. This constituent is effective to reduce the
tackiness of the copolymer. However, such hydrophilic
constituent may cause a disadvantageous decrease in the
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index of refraction of the final IOL optic in that some
water is included within the copolymer.
LeBoeuf et al U.S. Patent 5,603,774 discloses plasma
treatment of the polymer surface to reduce tackiness
associated with certain acrylic polymers, particularly
those polymers useful in intraocular lenses. However, such
plasma treatment does involve an additional manufacturing
step. Also, the non-homogeneous intraocular lens which
results from the surface being treated with plasma has the
potential of causing problems in the eye.
It would be advantageous to provide ophthalmic lens
materials of construction which have good optical
properties, including optical clarity and high refractive
index (index of refraction) and, in addition, have reduced
tackiness without the disadvantages of the prior art
materials noted above.
Summary of the Invention
New polymeric materials and ophthalmic lenses, for
example, IOLs, produced from such polymeric materials have
been discovered. The present polymeric materials are
derived from a combination of monomers and provide very
useful optical properties in terms of optical clarity and
high index of refraction and can be formed into ophthalmic
lenses, for example, optics of IOLs which are effectively
deformable, preferably foldable, for insertion through
small surgical incisions, preferably on the order of about
3 mm or less (in maximum transverse dimension).
Importantly, the present compositions and ophthalmic lenses
have reduced surface tackiness without requiring the
presence of fluoroacrylates, hydrophilic components and
without requiring plasma treatment. By selecting the
monomeric components used to produce the present
compositions and ophthalmic lenses in accordance with the
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present invention, reduced surface tackiness is achieved
with little or no adverse impact on the optical clarity,
refractive index, homogeneity, biocompatability,
deformability, and cost of production of such compositions
and ophthalmic lenses. The present compositions and lenses
can be produced using conventional techniques, e.g.,
conventional polymerization techniques. Thus, the present
invention is very effective and easy to practice and
results in polymeric compositions and ophthalmic lenses
which have outstanding properties.
In one broad aspect of the present invention,
ophthalmic lens bodies are provided which comprise cross-
linked polymeric materials or compositions. Such materials
comprise a first constituent derived from a first monomeric
component selected from acrylates, methacrylates and
mixtures thereof. A second constituent is included and is
derived from a second component in an amount effective as
a cross linker in the cross-linked polymeric material. The
cross-linked polymeric material has branched chain alkyl
groups in an amount effective to reduce the tackiness of
the cross-linked polymeric material relative to a
substantially identical cross-linked polymeric material
without the branched chain alkyl groups. It has been found
that the inclusion of branched chain alkyl groups, for
example, in the first monomeric component, or portion
thereof, unexpectedly provides reduced surface tackiness to
the cross-linked polymeric material. Thus, this reduced
tackiness is obtained without requiring the presence of a
fluoroacrylate or a hydrophilic component and without
requiring treating, for example, plasma treating, the
surface of the polymeric material.
The present ophthalmic lens bodies may be in the form
of optics of IOLs, contact lenses, corneal implants (for
example, corneal onlays and corneal inlays) and other
ophthalmic lens bodies. The present lens bodies are
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particularly useful as optics of IOLs, more preferably
deformable IOLs. Because a deformable IOL is adapted to be
deformed, that is rolled, folded or otherwise deformed,
prior to insertion into the eye, it is important that the
5 IOL optic have a relatively reduced degree of surface
tackiness to provide for effective deforming for insertion
and/or to allow the optic to effectively regain its
original shape in the eye.
The term "branched chain alkyl groups", as used
herein, refers to alkyl groups which are non-linear. Thus,
at least one, and preferably more than one, carbon atom in
the alkyl group is located in one or= more branches, rather
than being located in a single linear portion of the alkyl
group. Also, cycloalkyl groups are, by definition,
branched chain alkyl groups. The branched chain alkyl
group may be of any size suitable to function as described
herein. Preferably, the branched chain alkyl group has
about 3 to about 20 carbon atoms and more preferably about
6 to about 15 carbon atoms.
The amount of branched chain alkyl groups present is
sufficient to provide a cross-linked polymeric material
having reduced tackiness relative to a substantially
identical cross-linked polymeric material without the
branched chain alkyl groups. The monomeric component, for
example, the first monomeric component, or portion thereof,
including the branched chain alkyl groups used in providing
the present cross-linked polymeric materials may represent
a wide ranging proportion of the total monomeric components
employed. Preferably, the branched chain alkyl group-
containing monomeric component, or portion thereof,
provides a constituent of the cross-linked polymeric
materials which is present in an amount in the range of
about 1% or less to about 50% or more, and more preferably
about 3% to about 25%, by weight of the cross-linked
polymeric material.
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The first monomeric component, or at least a portion
thereof, preferably is selected from acrylates including a
branched chain alkyl group, methacrylates including a
branched chain alkyl group and mixtures thereof. In one
useful embodiment, the cross-linked polymeric material
includes a third constituent derived from a third monomeric
component other than the first and second monomeric
components. This third monomeric component is selected
from acrylates, methacrylates and mixtures thereof.
Preferably, the first monomeric component is selected from
acrylates having a branched chain alkyl group and mixtures
thereof. The third monomeric component preferably is
selected from methacrylates and mixtures thereof.
In one embodiment the present cross-linked polymeric
material has reduced tackiness relative to a substantially
identical cross-linked polymeric material in which the
first constituent is replaced by a constituent derived from
a monomeric component having a straight chain alkyl group
having the same number of carbon atoms as the branched
chain alkyl groups of the first monomeric component.
Advantageously, the cross-linked polymeric material
has an index of refraction of at least about 1.50.
Relatively high indexes of refraction allow the ophthalmic
lenses, and in particular IOLs, to be conveniently
manufactured with relatively high optical powers and the
capability of being passed through scleral tunnel incisions
of about 3.0 mm or even about 2.8 mm or less. Preferably,
the cross-linked polymeric material includes aryl-
containing groups in an amount effective to increase the
index of refraction of the cross-linked polymeric material
relative to the index of refraction of a substantially
identical cross-linked polymeric material without the aryl-
containing groups. In a very useful embodiment, the third
monomeric component includes an effective amount of aryl-
containing groups to increase the index of refraction of
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the cross-linked polymeric material, as desired.
In order to provide the desired degree of
deformability, the cross-linked polymeric material
preferably has a glass transition temperature (Tg) of about
22 C or less. Thus, in the context of an IOL optic, a
cross-linked polymeric material having a Tg within this
preferred range can be folded or otherwise deformed for
insertion at or about room temperature. -
Each individual feature and each combination of two or
more features described herein are included within the
scope of the present invention provided that the features
included in the combination are not mutually inconsistent.
These and other aspects of the present invention are
set forth in the following detailed description, examples
and claims, particularly when considered in conjunction
with the accompanying drawings in which like parts bear
like reference numerals.
Brief Description of the Drawinas
Fig. 1 is a plan view of an IOL in accordance with the
present invention.
Fig. 2 is a side view of the IOL of Fig. 1.
Detailed Description of the Invention
The present ophthalmic lens bodies comprise cross-
linked polymeric materials as described herein. Such
cross-linked polymeric materials comprise a combination of
constituents derived from different monomeric components.
Thus, the present cross-linked polymeric materials comprise
a first constituent and a second constituent, and
preferably a third constituent.
The first constituent of the present cross-linked
polymeric materials is derived from a first monomeric
component selected from the group consisting of acrylates,
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methacrylates and mixtures thereof. At least a portion of
the first monomeric component preferably is selected from
acrylates including a branched chain alkyl group,
methacrylates including a branched chain alkyl group and
mixtures thereof.
The present cross-linked polymeric materials have
branched chain alkyl groups in an amount effective to
reduce the tackiness of the cross-linked polymer-ic
materials relative to a substantially identical cross-
linked polymeric materials without the branched chain alkyl
groups. When, as is preferred, the first monomeric
component, or portion thereof, includes branched chain
alkyl groups, such first monomeric component, or portion
thereof, is preferably present in an amount to provide an
effective tackiness reducing amount of the branched chain
alkyl groups.
The branched chain alkyl group-containing monomeric
component, for example, the first monomeric component, or
portion thereof, preferably provides a constituent of the
cross-linked polymeric material which is present in an
amount in the range of about 1% or less to about 50% or
more, more preferably about 3% to about 25% by weight, of
the total cross-linked polymeric material.
Homopolymers of the first monomeric component
preferably have a Tg of less than about 30 C, more
preferably less than about 22 C.
Typical examples of the first monomeric component
include, but are not limited to 2-ethyihexyl acrylate, 2-
ethylhexyl methacrylate, 2,2-dimethylpropyl acrylate, 2,2-
dimethylpropyl methacrylate, trimethylcyclohexyl acrylate,
trimethylcyclohexyl methacrylate, isobutyl acrylate,
isobutyl methacrylate, isopentyl acrylate, isopentyl
methacrylate and mixtures thereof.
The second constituent of the present cross-linked
polymeric materials is derived from a second monomeric
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component in an amount effective as a crosslinker in the
present cross-linked polymeric materials. This second
monomeric component preferably is multi-functional and can
chemically react with the first monomeric component, and
more preferably with both the first and third monomeric
components. The second constituent of the present cross-
linked polymeric materials is present in an amount
effective to provide a desired degree of shape memory to
the materials, for example, to facilitate returning a
deformed IOL made from the present cross-linked polymeric
material to its original shape, for example, in a
reasonable period of time, at the conditions present in the
human eye.
The second or cross linking monomeric component is
often present in a minor amount relative to the amounts of
the first and third monomeric components. Preferably, the
second constituent is present in the cross-linked polymeric
material in an amount of less than about 1% by weight of
the material. The second constituent of the present cross-
linked polymeric materials may be considered to be a cross
linker. The cross linking monomeric component is often
selected from multi functional components, preferably able
to chemically react with at least one functional group of
each of the first monomeric component and the third
monomeric component. The cross linking monomeric component
is chosen to be chemically reactable with at least one
functional group associated with one or both of the first
monomeric component and the third monomeric component.
Examples of the second monomeric component for use in
the present cross-linked polymeric materials include, but
are not limited to, ethylene glycol dimethacrylate,
tetraethylene glycol dimethacrylate, allyl acrylate, allyl
methacrylate, trifunctional acrylates, trifunctional
methacrylates, tetrafunctional acrylates, tetrafunctional
methacrylates and mixtures thereof.
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The third monomeric component used in producing the
cross-linked polymeric materials of the present invention
is different from the first and second monomeric
components. Such third monomeric component is selected
5 from acrylates, methacrylates and mixtures thereof. The
third constituent of the present cross-linked polymeric
materials preferably is present to provide a constituent of
the cross-linked polymeric material in an amount of -at
least about 100 or about 20% by weight, and more preferably
10 in a major amount (at least about 50%) by weight, of the
cross-linked polymeric material. In one very useful
embodiment, the third constituent is derived from a third
monomeric component the homopolymers of which have an index
of refraction of at least about 1.50, preferably at least
about 1.52 or about 1.54. The homopolymers of the third
monomeric component may have a substantial degree of
rigidity.
In one particularly useful embodiment, the first and
third constituents together are preferably at least about
80%, more preferably at least about 90%, by weight of the
present cross-linked polymeric materials. The first and
third monomeric components preferably are selected so that
each of these monomeric components can chemically react
with the other monomeric component.
The present cross-linked polymeric materials have
reduced surface tackiness and preferably are optically
clear and have high indexes of refraction, for example, at
least about 1.50, and preferably at least about 1.52 or at
least about 1.54.. The combination of properties of the
present cross-linked polymeric materials, for example,
which facilitates the manufacture of effectively deformable
IOLs having high optical power, is very advantageous.
As used herein, the term "homopolymer" refers to a
polymer which is derived substantially completely from the
monomeric component in question. Thus, such homopolymer
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includes as the primary, preferably sole, monomeric
component, the monomeric component in question. Minor
amounts of catalysts, initiators and the like may be
included, as is conventionally the case, in order to
facilitate the formation of the homopolymer. In addition,
the homopolymers of both the first monomeric component and
the third monomeric component have sufficiently high
molecular weights or degrees of polymerization so as to -be
useful as IOL materials of construction.
The homopolymers of the third monomeric component may
be rigid. An IOL made from such a"rigid" homopolymer is
not deformable, for example, using systems which are
specifically structured and used to deform IOLs for
insertion through a small incision into the eye. The
rigidity of the homopolymer of the third monomeric
constituent may result in an IOL made from such homopolymer
being not deformable, or breaking or otherwise
deteriorating as a result of the application of force
seeking to so deform such IOL for implantation through a
small ocular incision.
The third constituent preferably is present in an
amount of at least about 10% or at least about 200, more
preferably in a major amount, by weight of the present
cross-linked polymeric materials. The third monomeric
component from which the third constituent is derived may
be selected from compounds which meet the criteria set
forth herein for such component. This monomeric component
preferably is such as to provide the present cross-linked
polymeric materials with increased refractive index
relative to the homopolymers of the first monomeric
component. The homopolymers of the third monomeric
component preferably have an index of refraction of at
least about 1.50, and more preferably at least about 1.52
or at least about 1.54.
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In one embodiment, the third monomeric component is
characterized as including one or more aryl-containing
groups. Without wishing to limit the present invention to
any particular theory of operation, it is believed that the
presence of such aryl-containing groups in the third
monomeric component at least facilitates, and preferably
leads to or results in, the present cross-linked polymeric
materials having desirably high refractive indexes. If the
third monomeric component includes one or more aryl-
containing groups, it is preferred t:hat at least the first
monomeric component, and more preferably that the first and
second monomeric components, include no aryl-containing
groups. This "single index of refraction control" is very
effective in achieving high index of refraction cross-
linked polymeric materials, and allows flexibility in
selecting the other monomeric component or components so
that cross-linked polymeric materials with advantageous
properties, other than index of refraction, for example,
cross-linked polymeric materials formable into IOLs which
can be effectively deformed (for insertion) at room
temperature, can be obtained.
Examples of the third monomeric component which may be
included in the present cross-linked polymeric materials
include, but are not limited to, benzyl acrylate, benzyl
methacrylate, phenyl acrylate, phenyl methacrylate,
phenoxyalkyl acrylates, phenoxyalkyl methacrylates,
phenylalkyl acrylates, phenylalkyl methacrylates, carbazole
acrylates, carbazole methacrylates, biphenyl acrylates,
biphenyl methacrylates, naphthyl acrylates, naphthyl
methacrylates and mixtures thereof.
Of course, the first, second and third monomeric
components should be such as to provide cross-linked
polymeric materia:ls which are compatible for use in or on
the eye, are optically clear and are otherwise suitable for
use as materials of construction for ophthalmic lenses. In
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one useful embodiment, each of the first, second and third
monomeric components is substantially free of silicon,.so
that the resulting copolymer is not a silicone polymer.
The monomeric components may be substituted with
substantially non-interfering substituents which have a
substantial detrimental effect on the cross-linked
polymeric materials produced therefrom. Such substituents
may include one or more elements, such as oxygen, nitrogen,
carbon, hydrogen, halogen, sulfur, phosphorus, and the like
and mixtures and combinations thereof.
The cross-linked polymeric materials of the present
invention preferably have glass transition temperatures
(Tg) of about 22 C or less. Such glass transition
temperatures (Tg) are beneficial in facilitating the
deforming (folding) of an IOL the optic of which is made of
an embodiment of the present cross-linked polymeric
material at room temperature prior to inserting the IOL
through a small incision into the eye.
The present cross-linked polymeric materials may be
produced using conventional polymerization techniques. For
example, the monomers can be blended together, cast into
the form of a sheet, and heated to ari elevated temperature,
such as in a range of about 50 C to about 90 C for a period
of time in a range of about 30 minutes to about 8 hours or
about 24 hours or more, to facilitate the polymerization
reaction. Catalysts and/or initiators, for example,
selected from materials well known for such use in the
polymerization art, may be included in the monomer mix in
order to promote, and/or increase the rate of, the
polymerization reaction. Examples of such initiators
include 2,2'-azobis (2,4-dimethylpentanenitrile), 2,2'-
azobis (2-methylpropanenitrile), 2,2'-azobis (2-
methylbutanenitrile), peroxides such as benzoyl peroxide,
W initiators such as dietho.:yacetophenone, and the like
and mixtures thereof.
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In addition, effective amounts of ultraviolet light
absorbing monomeric components, such as functional
benzotriazole and benzophenone derivatives, may be included
in the precursor monomer mix. Such UV light absorbing
monomeric components are polymerized into the final cross-
linked polymeric material to provide the final material
with effective UV light absorbing properties.
In one particularly useful embodiment, the present
cross-linked polymeric materials are produced by mixing
together the first monomeric component and the third
monomeric component. This mixture is well blended,
deareated and heated to a temperature, for example, of
about 50 C to about 80 C and maintained at this temperature
for a period of time, for example, of about 15 minutes to
about 3 hours. The mixture undergoes partial
polymerization to form a viscous liquid when cooled to
about 25 C.
The final cross-linked polymeric materials can be
produced by combining this partially polymerized viscous
liquid, the second or cross linking monomeric component and
catalyst and/or an initiator. Alternately, all the
monomeric components and catalyst and/or initiator can be
combined or mixed together. The viscous liquid, or
monomeric mixture, is well blended, deareated and poured
into a mold. The mold is heated, preferably to a
temperature of about 40 C to about 100 C, and the liquid or
mixture is allowed to cure, preferably for about 1 hour to
about 24 hours. The material in the mold is then post-
cured, preferably at a temperature in the range of about
70 C to about 130 C, for a period of time, preferably for
about 2 to about 30 hours. After curing (and post-curing),
the mold is disassembled and the molded lens body
recovered.
Alternately, the curing and post-curing occurs in a
tube. The cross-linked polymeric material formed in the
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tube is cut into cylindrical lens blanks. The lens blanks
can be machined to produce the finished lens body, e.g.,
IOL optic. Such machining may involve milling and lathing
at cryogenic temperatures.
5 Referring now to Figs. 1 and 2, IOL 21 is illustrated
as including a pair of radially outwardly extending haptics
or fixation members 28 secured to optically clear optic 26.
Alternately, the optic and fixation members can be formed
from a single piece of material. Each haptic 28 has a
10 substantially uniform cross section throughout its length
and is shown provided with a smoothly curved region 32,
intermediate a lens bonding region 34 and a free end region
36. Although the illustrated embodiment is provided with
two opposing haptics 28, it is understood that an IOL
15 having only one haptic or more than two haptics bonded to
the optic is within the scope of the invention.
Optic 26 is made of a cross-linked polymeric material
in accordance with the present invention, for example, the
material as set forth in Example 1 hereof. Optic 26 can be
formed in accordance with conventional IOL optic forming
techniques, such as by injection molding, sheet casting and
cutting to form bottons and the like techniques.
Alternately, the monomeric components can be first mixed in
a tube and then cured in the tube. The resulting rod then
is cut into buttons which are then cryolathed into IOL
optics.
Typically, each haptic 28 comprises a flexible member
comprising metal or, preferably, polymeric material, and
having a substantially circular cross-section, although
alternative cross-sectional configurations may be
substituted, if desired. Although the haptics may take on
any suitable configuration, the illustrated haptics 28 are
relatively thin and flexible, while at the same time being
sufficiently strong to provide support for IOL 21 in eye
10. The haptics 28 may comprise any of a variety of
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materials which exhibit sufficient supporting strength and
resilience, and which are substantially biologically inert
in the intended in vivo environment. Suitable materials
for this purpose include, for example, polymeric materials
such as polyamides, polyimides, polyacrylates, 2-hydroxy-
methylmethacrylate, poly (vinylidene fluoride),
polytetrafluoroethylene and the like; and metals such as
stainless steel, platinum, titanium, tantalum, shape-memo-ry
alloys, e.g., nitonal, and the like. The haptics can be
produced using conventional and well known forming
techniques. For example, the preferred polymeric haptics
can be formed in accordance with known thermoplastic
polymer forming techniques, such as by injection molding or
by extrusion.
The lens bonding regions 34 of the haptics 28, which,
as described herein, are secured to optic, may be provided
with any of a variety of configurations, such as an
anchoring loop, an anchoring "T", or other anchor
structure, to provide a mechanical interlock with the
optic, such as has been done in the prior art.
IOL 26 can be formed using any one of various
techniques, such as those conventionally used to form IOLs.
For example, the lens bonding regions 34 of haptics 28 can
be placed in a mold which is filled with a mix of the
monomeric components used to form the optic 26. The mold
is then subjected to conditions, e.g., elevated
temperature, effective to form the cross-linked polymeric
materials of the present invention from this monomer mix.
The lens bonding regions 34 become bonded to the optic 26,
thereby securing the haptics 28 to the optic. Alternately,
the haptics 28 can be secured in recesses provided in the
already formed optic 26.
Optic 26 has low or reduced surface tackiness, and
preferably an index of refraction of at least about 1.50.
Optic 26 is foldable for insertion into a human eye through
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an incision of about 3mm in length. After insertion into
the eye in the folded condition, IOL 21 returns to its
original shape in a reasonable period of time, for example,
on the order of about 1 second or about 20 seconds to about
three minutes, and can be easily positioned in the eye for
effective and long term use as a replacement for the
natural lens normally present in the eye.
The following non-limiting examples illustrate certa-in
aspects of the present invention.
EXAMPLE 1
The followirlg formulation is blended, purged with
nitrogen for 3 minutes and then cured into a cross-linked
copolymer.
Weight %
2-Phenoxyethyl acrylate 32.5
2-Phenoxyethyl methacrylate 48.7
3,5,5-trimethylhexyl acrylate 14.7
Ethylene glycol dimethacrylate 2.0
Ultraviolet light absorbing
Monomeric component 2.0
Radical initiator (2) 0.11
'1' 2-(4-benzoyl-4-hydroxyphenoxy)ethylacrylate
12' 2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane
The resulting cross-linked copolymer has an index of
refraction of 1.54, a glass transition temperature (Tg) of
15 C, excellent optical transparency (clarity) and good
mechanical properties, including low or reduced tackiness.
A one cm diameter rod of this copolymer is folded 180 with
no cracking and returns to its original shape within a few
seconds at 35 C.
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EXAMPLE 2
Using conventional techniques, an optic is formed from
the crosslinked copolymer produced in Example 1. In order
to produce a 20 diopter, plano-convex optic, having a 0.305
mm edge thickness and a 6.0 mm diameter, the optic center
thickness is approximately 0.737 mm.
EXAMPLE 3
An IOL is produced having an optic as indicated in
Example 2. Two substantially opposing haptics, such as
shown in Figs. 1 and 2, made from extruded poly methyl
methacrylate filaments are bonded to this optic. The
resulting IOL is inserted into the eye through a 3 mm
surgical incision. In order to accomplish such insertion,
the IOL is folded. Upon being released into the eye, the
IOL regains its original shape in less than one minute and
is fixed in position in the eye. After normal healing, the
IOL is effective and useful in the eye as a replacement for
the natural lens normally present in the eye.
EXAMPLE 4
The cross-linked polymer of Example 1 (Example 1
Copolymer) and a cross-linked copolymer similar to the
cross-linked copolymer produced in Example 1 (Example 4
Copolymer) are made or cast in the form of sheets. Both
copolymers are made in a manner similar to how the
copolymer of Example 1 is made. The composition of the
Example 4 Copolymer is similar to the copolymer of Example
1 except that n-nonyl acrylate is used in place of 3,5,5-
trimethylhexyl acrylate.
A series of discs shaped and sized similar to optics
of intraocular lenses are produced from each of these
sheets. A lens folding forceps is used to fold these discs
in half (180 ) . After holding the folded disc in the
forceps for 30 seconds, the disc is released from the
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WO 00/26698 PCTIUS99/24982
19
forceps into a beaker containing water at 35 C. The amount
of time required for the disc to release from itself,
referred to as the "tack time", is recorded. Also, the
amount of time required of the disc to return to flatness
or its original shape, referred to as the "unfold time", is
recorded.
Results of these tests are as follows:
Disc Material Tack Time, Unfold Time,
seconds seconds
1 Example 1 Copolymer 19 35
2 Example 1 Copolymer 17 44
3 Example 1 Copolymer 12 34
4 Example 1 Copolymer 11 33
5 Example 1 Copolymer 26 46
AVERAGE 17 38
6 Example 4 Copolymer 33 41
7 Example 4 Copolymer 32 42
8 Example 4 Copolymer 51 62
9 Example 4 Copolymer 34 45
10 Example 4 Copolymer 23 33
AVERAGE 35 45
These results demonstrate that the Example 1 Copolymer
has reduced tackiness relative to the Example 4 Copolymer.
Since substantially the only difference in these two
materials is the presence of a monomer including a branched
chain alkyl group, that is 3,5,5-trimethylhexyl acrylate,
in the Example 1 Copolymer, these results make clear that
this type of monomer is surprisingly effective in
advantageously reducing the tackiness of cross-linked
copolymers derived from such monomers, and in particular
ophthalmic lenses including such copolymers.
While this invention has been described with respect
to various specific examples and embodiments, it is to be
understood that the invention is not limited thereto and
that it can be variously practiced within the scope of the
CA 02348495 2007-07-18
following claims.
