Intraocular lenses made from polymeric compositions and monomers useful in said compositions

Ophthalmic lenses, such as intraocular lenses, include crosslinked polymeric materials having a first constituent derived from a first monomeric component selected from the group consisting of 2-phenylpropyl acrylate or methacrylate and mixtures thereof, and a second constituent derived from a second component in an amount effective as a crosslinker in the crosslinked polymeric material. The crosslinked polymeric material has branched chain alkyl groups, in an amount effective to reduce the tackiness of the crosslinked polymeric material relative to a substantially identical crosslinked polymeric material without branched chain alkyl groups.

BACKGROUND OF THE INVENTION
 (1) Field of the Invention
 The present invention relates to ophthalmic lenses made from polymeric
 compositions and novel monomers useful in said compositions. More
 particularly, the invention relates to ophthalmic lenses, preferably
 deformable intraocular lenses, having reduced surface tackiness made from
 2-phenylpropylacrylate and/or methacrylate-based polymeric compositions.
 (2) Description of Related Art
 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 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 smaller 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. Pat. No. 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 crosslinked 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. Pat. No. 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 index of refraction of the final IOL optic
 in that some water is included within the copolymer.
 LeBoeuf et al U.S. Pat. No. 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.
 Monomers useful in preparing acrylic polymers and co-polymers are well
 known. For example, see RN 133832-56-1 REGISTRY which discloses
 homopolymers of 2-propenoic acid, 2-methyl-,2-methyl-3-phenylpropyl
 ester(s)-, (2-propenoic acid, 2-methyl-3-phenylpropyl ester?)homopolymer.
 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.
 Furthermore, it would be advantageous to provide novel monomers which are
 useful in the preparation of such ophthalmic lens materials.
 BRIEF 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 2-phenylpropyl acrylate and/or 2-phenylpropyl
 methacrylate 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
 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 crosslinked polymeric materials or compositions.
 Such materials comprise a first constituent derived from a first monomeric
 component selected from acrylates, methacrylates and mixtures thereof.
 Such first constituent will include at least one of 2-phenylpropyl
 acrylate or 2-phenylpropyl methacrylate as a monomer. A second constituent
 is included and is derived from a second component in an amount effective
 as a cross-linker in the crosslinked polymeric material. The resulting
 crosslinked polymeric material includes 2-phenylpropyl acrylate or
 2-phenylpropyl methacrylate in an amount effective to reduce the tackiness
 of the crosslinked polymeric material relative to a substantially
 identical crosslinked polymeric material without branched chain alkyl
 groups. It has been found that the inclusion of 2-phenylpropyl acrylate or
 2-phenylpropyl methacrylate, for example, in the first monomeric
 component, or portion thereof, unexpectedly provides reduced surface
 tackiness to the crosslinked 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
 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 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 amount of 2-phenylpropyl acrylate or 2-phenylpropyl methacrylate
 present is sufficient to provide a crosslinked polymeric material having
 reduced tackiness relative to a substantially identical crosslinked
 polymeric material without branched chain alkyl groups. The monomeric
 component, for example, the first monomeric component, or portion thereof,
 including 2-phenylpropyl acrylate or 2-phenylpropyl methacrylate used in
 providing the present crosslinked polymeric materials may represent a wide
 ranging proportion of the total monomeric components employed. Preferably,
 the 2-phenylpropyl acrylate or 2-phenylpropyl methacrylate-containing
 monomeric component, or portion thereof, provides a constituent of the
 crosslinked polymeric materials which is present in an amount in the range
 of about 1% or less to about 95% or more, and more preferably about 10% to
 about 85%, by weight of the crosslinked polymeric material.
 In one useful embodiment, the crosslinked 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. The third
 monomeric component preferably is selected from acrylates and mixtures
 thereof.
 In one embodiment the present crosslinked polymeric material has reduced
 tackiness relative to a substantially identical crosslinked polymeric
 material in which the first constituent is replaced by a constituent
 derived from a monomeric component having a straight chain alkyl group or
 phenyl-n-alkyl group having about the same number of carbon atoms as the
 2-phenylpropyl acrylate or methacrylate included in the first monomeric
 component, i.e. an acrylate or methacrylate ester having from about 7 to
 about 9 carbons in the ester chain, such as, e.g. n-octyl or phenylethyl
 acrylate or methacrylate monomers.
 Advantageously, the crosslinked polymeric material is 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 crosslinked polymeric material
 includes aryl-containing groups from the 2-phenylpropyl acrylate or
 2-phenylpropyl methacrylate monomer in an amount effective to increase the
 index of refraction of the crosslinked polymeric material relative to the
 index of refraction of a substantially identical crosslinked polymeric
 material without the aryl-containing groups.
 In order to provide the desired degree of deformability, the crosslinked
 polymeric material preferably has a glass transition temperature (Tg) of
 about 22.degree. C. or less. Thus, in the context of an IOL optic, a
 crosslinked 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.

DETAILED DESCRIPTION OF THE INVENTION
 The present ophthalmic lens bodies comprise crosslinked polymeric materials
 as described herein. Such crosslinked polymeric materials comprise a
 combination of constituents derived from different monomeric components.
 Thus, the present crosslinked polymeric materials comprise a first
 constituent and a second constituent, and preferably a third constituent.
 The first constituent of the present crosslinked polymeric materials is
 derived from a first monomeric component selected from the group
 consisting of 2-phenylpropyl acrylate, 2-phenylpropyl methacrylate and
 mixtures thereof.
 The present crosslinked polymeric materials have 2-phenylpropyl acrylate or
 2-phenylpropyl methacrylate in an amount effective to reduce the tackiness
 of the crosslinked polymeric materials relative to a substantially
 identical crosslinked polymeric materials having a normal alkyl side
 chains of from about 7 to about 9 carbons or phenyl-n-alkyl side chains of
 from about 7 to about 9 carbons.
 The 2-phenylpropyl acrylate or 2-phenylpropyl methacrylate monomeric
 component, for example, the first monomeric component, or portion thereof,
 preferably provides a constituent of the crosslinked polymeric material
 which is present in an amount in the range of about 1% or less to about
 95% or more, more preferably about 3% to about 85% by weight, of the total
 crosslinked polymeric material.
 The homopolymers of 2-phenylpropyl acrylate or 2-phenylpropyl methacrylate
 have an index of refraction of at least about 1.50, preferably at least
 about 1.52 or about 1.54.
 The second constituent of the present crosslinked polymeric materials is
 derived from a second monomeric component in an amount effective as a
 crosslinker in the present crosslinked 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 crosslinked 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 crosslinked
 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 crosslinking 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
 crosslinked polymeric material in an amount of less than about 5% by
 weight of the material. The second constituent of the present crosslinked
 polymeric materials may be considered to be a crosslinker. The
 crosslinking 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 crosslinking monomeric component is chosen to be
 chemically reactible 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
 crosslinked polymeric materials include, but are not limited to, ethylene
 glycol dimethacrylate tetraethylene glycol dimethacrylate, allyl acrylate,
 ally. methacrylate, trifunctional acrylates, trifunctional methacrylates,
 tetrafunctional acrylates, tetrafunctional methacrylates and mixtures
 thereof.
 The third monomeric component used in producing the crosslinked polymeric
 materials of the present invention is different from the first and second
 monomeric components. Such third monomeric component is selected from
 acrylates, methacrylates and mixtures thereof. The third constituent of
 the present crosslinked polymeric materials preferably is present to
 provide a constituent of the crosslinked polymeric material in an amount
 of at least about 10% or about 20% by weight, of the crosslinked polymeric
 material.
 In one particularly useful embodiment, the first and third constituents
 together are preferably at least about 80%, more preferably at least about
 95%, by weight of the present crosslinked 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 crosslinked 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 crosslinked
 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 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 first 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 first 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 first constituent preferably is present in an amount of at least about
 10% or at least about 20%, more preferably in a major amount, by weight of
 the present crosslinked 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. The monomeric
 component of the first constituent preferably is such as to provide the
 present crosslinked polymeric materials with increased refractive index
 relative to the homopolymers of the third monomeric component. The
 homopolymers of the first 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.
 Without wishing to limit the present invention to any particular theory of
 operation, it is believed that the presence of aryl-containing groups in
 the monomers at least facilitates, and preferably leads to or results in,
 the present crosslinked polymeric materials having desirably high
 refractive indexes. It is preferred that at least the third monomeric
 component, and more preferably that the third and second
 monomeric-components, include no aryl-containing groups. This "single
 index of refraction control" is very effective in achieving high index of
 refraction crosslinked polymeric materials, and allows flexibility in
 selecting the other monomeric component or components so that crosslinked
 polymeric materials with advantageous properties, other than index of
 refraction, for example, crosslinked polymeric materials formable into
 IOLs which can be effectively deformed (for insertion) at room
 temperature, can be obtained.
 Typical examples of the third monomeric component include, but are not
 limited to n-butylacrylate, n-hexyl acrylate, n-octyl acrylate, n-butyl
 methacrylate, n-hexyl methacrylate, n-octyl methacrylate, 2-ethylhexyl
 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.
 More preferably, to further reduce tackiness, the third monomeric component
 may include a branched chain alkyl ester, e.g. 2-ethylhexyl 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.
 Of course, the first, second and third monomeric components should be such
 as to provide crosslinked polymeric materials 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 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 crosslinked 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 crosslinked polymeric materials of the present invention preferably
 have glass transition temperatures (Tg) of about 22.degree. 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 crosslinked polymeric material at room temperature prior to
 inserting the IOL through a small incision into the eye.
 The present crosslinked polymeric materials may be produced using
 conventional polymerization techniques. For example, the monomers can be
 blended together and heated to an elevated temperature 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, UV initiators such as diethoxyacetophenone, and
 the like and mixtures thereof.
 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 crosslinked polymeric
 material to provide the final material with effective UV light absorbing
 properties.
 In one particularly useful embodiment, the present crosslinked 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.degree. C. to about
 80.degree. 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.degree. C.
 The final crosslinked polymeric materials can be produced by combining this
 partially polymerized viscous liquid, the second or crosslinking 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.degree. C. to about 100.degree. 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.degree. C. to about 130.degree. 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 crosslinked
 polymeric material formed in the 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.
 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. Each haptic 28 has a 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 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 crosslinked 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 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 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 polypropylene polyamides, polyimides,
 polyacrylates, 2-hydroxyethyl methacrylate, poly (vinylidene fluoride),
 polytetrafluoroethylene and the like; and metals such as stainless steel,
 platinum, titanium, tantalum, shape-memory 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
 crosslinked 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 an incision of about 3 mm 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 certain aspects of the
 present invention.
 EXAMPLE 1
 Synthesis of 2-phenylpropyl methacrylate
 This monomer is prepared as follows:
 A two-mouth one-liter round bottom flask containing a magnetic stir bar is
 lowered into an ice bath on top of a magnetic stirrer. 25 grams (0.18 mol)
 of 2-phenyl-1-propanol is added into the flask, followed by the addition
 of 30 ml (0.22 mol) of triethylamine to the flask. The now empty
 triethylamine addition flask is rinsed with about 10-ml of anhydrous
 diethyl ether and this is added to the round bottom flask. Another 200 ml
 of anhydrous diethyl ether is added to the round bottom flask, followed by
 5 mg (0.0002 mol) of inhibitor (2,5-diphenyl-p-benzophenone). The magnetic
 stirrer stirs the resulting mixture at 555 rpm.
 100 ml of anhydrous diethyl ether and 20-ml (0.21 mol) methacryloyl
 chloride are added, dropwise, while the contents of the flask are
 maintained at about 2.degree. C. The methacryloyl chloride addition are
 adjusted so that the addition is completed in about 1 1/2 hours. The
 reaction mix is allowed to continue to stir for about 24 hours and then
 quenched by adding about 200 ml of distilled water to the reaction
 mixture. The lower aqueous layer of the quenched mixture is discarded and
 the remaining organic layer is dried with magnesium sulfate (MgSO.sub.4)
 The organic solution is decanted and about 5 mg of inhibitor
 (2,5-diphenyl-p-benzophenone) is added thereto. Another 5 mg of inhibitor
 (2,5-diphenyl-p-benzophenone), is added along with a few boiling chips,
 prior to distilling the decanted solution under vacuum (ca. 200 millitorr)
 while stirring magnetically. The oil bath temperature is raised in stages
 from 50.degree. C. to 80.degree. C. in order to initially facilitate the
 removal of solvent. The distillation may take up to 2 hours or more to
 complete depending upon the vacuum attained.
 The first five-ml of distillate that distills at around 60.degree. C. and
 200 millitorr is collected. The remainder of the distillate is collected
 and the final product structure is confirmed by proton NMR analysis.
 EXAMPLE 2
 Synthesis of 2-phenylpropyl acrylate
 The above monomer is prepared as in Example 1 except that acryloyl chloride
 replaces methacryloyl chloride on an equal molar basis.
 EXAMPLE 3
 The following formulation is blended, purged with nitrogen for 3 minutes
 and then cured into a crosslinked copolymer.

Quantity % Quantity
 2-phenylpropyl methacrylate 15.0 g 33.4%
 2-phenylpropyl acrylate 21.5 g 47.9%
 n-hexyl acrylate 6.5 g 14.5%
 EGDMA ethylene glycol dimethacrylate 0.9 g 2.0%
 thermal initiator 0.1 g 0.2%
 (2,5-dimethyl-2,5
 bis(2-ethylhexanoylperoxy) hexane
 UV absorber 0.9 g 2.0%
 The resulting crosslinked copolymer has an index of refraction of 1.5396,
 hardness (Shore A) of 42, haze (after soaking) of 3, excellent optical
 transparency (clarity) and good mechanical properties, including low or
 reduced tackiness. A one cm diameter rod of this copolymer is folded
 180.degree. with no cracking and returns to its original shape within a
 few seconds.
 EXAMPLE 4
 Using conventional techniques, an optic is formed from the crosslinked
 copolymer produced in Example 3. 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 5
 An IOL is produced having an optic as indicated in Example 4. 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 6
 The crosslinked polymer of Example 3 (Example 3 Copolymer) and a
 crosslinked copolymer similar to the crosslinked copolymer produced in
 Example 3 (Example 6 Copolymer) are made or cast in the form of sheets.
 Both copolymers are made in a manner similar to how the copolymer of
 Example 3 is made. The composition of the Example 6 Copolymer is similar
 to the copolymer of Example 3 except that n-nonyl acrylate is used in
 place of 2-phenylpropyl acrylate or methacrylate.
 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.degree.). After holding the folded disc in
 the forceps for 30 seconds, the disc is released from the forceps into a
 beaker containing water at 35.degree. 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 demonstrate that the Example 3 Copolymer has reduced
 tackiness relative to the Example 6 Copolymer. Since substantially the
 only difference in these two materials is the presence of 2-phenylpropyl
 acrylate or methacrylate, in the Example 3 Copolymer, these results make
 clear that this type of monomer is surprisingly effective in
 advantageously reducing the tackiness of crosslinked 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 following claims. For example, the IOL may be a disc lens, i.e. no
 haptics.