EP1166155A1

EP1166155A1 - Polymeric material compositions and intraocular lenses made from same

Info

Publication number: EP1166155A1
Application number: EP00918347A
Authority: EP
Inventors: Stephen Q. Zhou
Original assignee: Medennium Inc
Current assignee: Medennium Inc
Priority date: 1999-03-23
Filing date: 2000-03-23
Publication date: 2002-01-02
Also published as: WO2000057213A1

Abstract

A deformable intraocular lens comprised of copolymers of methacrylate esters having general formulae (I) and (II) wherein R and R' are independently n-alkyl, sec-alkyl, iso-alkyl, tert-alkyl, other isomeric alkyl radicals, substituted alkyl radicals containing oxygen and substituted alkyl radicals containing nitrogen and R'' is included to modify the hydrophobicity of the copolymer are disclosed. Preferably, R and R' are C1-C20, branched or linear alkyl radicals, wherein R' contains only aliphatic alkyls and more preferably, R=CH3 so that one of the monomers is methylmethacrylate (MMA). Optionally included for formulae (I) and (II) is a cross-linking monomer having a plurality of polymerizable ethylenically unsaturated groups. Still optionally, an ultraviolet absorbing material (UV absorber) with a polymerizable functional group is also incorporated into the copolymer. These methacrylate copolymers can be used to form intraocular lenses that have an essentially tack-free surface, a glass transition temperature (Tg) below about 37 °C, a tensile strength from about 100 psi to about 1000 psi, and a refractive index from about 1.47 to about 1.49. These lenses are flexible and transparent, capable of being inserted into the eye through a relatively small incision, and recover to their original shape after insertion into the eye.

Description

POLYMERIC MATERIAL COMPOSITIONS AND INTRAOCULAR LENSES MADE FROM SAME

This application is based on U.S. Provisional Patent Application Serial No. 60/125,758, Zhou, filed March 23, 1999.

Technical Field The present invention relates generally to polymer compositions and their use in optical lenses. More particularly, the present invention is directed to deformable intraocular lenses made from copolymers of methacrylate esters.

Background The natural eye contains an internal crystalline lens, which focuses images on the retina. Either through disease or other naturally occurring processes, or mutations, this lens may fail to function properly. For instance, the lens may be cloudy at birth or become cloudy over time. This clouding of the lens is known as a cataract, which inhibits the transmission of visual information through the lens to the retina. The removal of diseased natural lenses has, prior to the advent of intraocular lenses, required a large incision into the eye at the junction of the cornea and the sclera in order to remove the lens. The healing time in such an operation was substantial and the pain was severe. No lens was inserted in place of the natural lens and eyeglasses or external-type contact lenses were employed to help restore vision to the patient. Intraocular lenses (IOLs) are now well-known replacements for natural crystalline lenses which have been surgically removed. Such intraocular lenses are generally surgically implanted directly into the eye and are intended to replace the damaged or diseased natural lens of the eye in order to restore a patient's vision. In order to surgically implant an IOL into the eye, a small incision is made into the eye in order to first remove the natural lens. It is desirable to keep this incision as small as possible. However, in order to successfully implant a rigid IOL into the eye, the average minimum size for the incision is typically from about 5 millimeters (mm) to about 6 mm. Such large incisions can give rise to various wound-related problems, including infection, wound leak and astigmatism. More recently, small incision surgery has become increasingly popular for IOL implantation. It is now possible to remove a natural lens using an incision no larger than 2-3 mm. However, since a rigid IOL is still from about 5-6 mm in diameter, an incision comparable to the diameter of the rigid IOL is still necessitated to permit the insertion of the rigid IOL.

Early designs of IOLs were generally manufactured and formed from poly(methylmethacrylate) (PMMA). PMMA is relatively light weight polymer which possesses excellent optical properties and is generally considered to be relatively inert when implanted into the eye, thereby avoiding adverse tissue reactions and thus is biocompatible. However, PMMA comprises a plastic matrix which, when formed into the shape of a lens, possesses high rigidity and cannot be deformed by folding, rolling, compression, etc. Accordingly, the use of PMMA lenses requires a relatively large incision in the ocular tissue sufficient to accommodate the entire diameter of the lens body which is typically six millimeters or larger, together with the accompanying lens support structures. While the rigid IOLs formed from PMMA have gained widespread acceptance and use, foldable IOLs were more recently introduced to overcome the problems associated with implantation of the rigid IOLs. Typically, a deformable IOL is designed to be implanted into a small incision (from about 3.5 mm to about 4.0 mm) while a hard PMMA lens typically requires a much larger incision (about 6.0 mm). Unlike IOLs made from PMMA, the primary medical benefit of these foldable IOLs is that the large incisions associated with the rigid IOLs are no longer necessitated. Since such soft IOLs are deformable and can be folded in half, these soft IOLs typically require substantially smaller incision sizes for implantation as compared to the incision size for implantation of the rigid IOLs having the same or comparable optical power. Moreover, the patient benefits from the use of a deformable IOL requiring the smaller incision size since this will result in an overall safer surgical procedure and reduce the likelihood of post-operative complications such as infections, postoperative astigmatism and also substantially reduce patient rehabilitation time.

These foldable IOLs can be made from various soft, deformable resilient biocompatible polymeric materials, such as silicone or other elastomers. For instance, Mazzocco, U.S. Pat. No. 4,573,998, discloses a deformable intraocular lens that can be rolled, folded, or stretched to fit through a relatively small incision. The deformable lens is inserted while it is held in its distorted configuration, then released inside the chamber of the eye, whereupon the elastic property of the lens causes it to resume its molded shape. Suitable materials for the deformable lens, disclosed by Mazzocco includes polyurethane elastomers, silicone elastomers, hydrogel polymer compounds, organic or synthetic gel compounds and combinations thereof.

Although these foldable IOLs can be simple to manufacture and use, there are problems associated with the use of these IOLs made from silicones and hydrogel materials. Lenses made from various silicones can have relatively low refractive indices. Therefore, in order to provide a lens of proper refractive power, foldable IOLs derived from silicones must be relatively thick. The thicker the lens, the more difficult it can be to deform or distort the lens into a shape that is capable of fitting into a small incision. Therefore, the distortion required to force such a thick lens through a small incision may exceed the IOL's elastic properties so when released, the IOL will tend to snap back or regain its unfolded shape too rapidly, resulting in the lens breaking and possibly damaging the integrity of the endothelial cell layer of the eye. In addition, the long-term stability of UN-absorbing silicone formulations is uncertain. As for hydrogels, it has been found that hydrogel materials when hydrated vary in composition including water content from lot to lot. Such variability induces a corresponding variability in the refractive power of IOL lens bodies formed of hydrogel material. Therefore, hydrogel IOLs need to be hydrated in order to determine their refractive power in an implanted state. Unfortunately, hydrated lenses cannot be safely stored in the wet state without losing sterilization. If they are subsequently dehydrated, the process of hydro thermal cycling reduces the tensile strength of the IOL material and may cause development of cracks in the lens body. Thus, the utility of IOLs made from such materials is somewhat limited. As an alternative in overcoming some of these disadvantages associated with deformable IOLs manufactured form silicones and hydrogels, deformable IOL materials have been developed which combine a higher refractive index with a lower elasticity. To this end, acrylic polymers have been used extensively because of their ease in preparation, high level of atacticity ensuring low crystallinity, good processing characteristics, high optical quality and long term stability to ultraviolet (UN) wavelengths of light. However, these materials also have properties that are undesirable for the manufacture of deformable IOLs. The deformable IOLs made of acrylic materials have a tendency to be too rigid and brittle for use at room temperature, which can result in cracking of the IOL if it is folded too quickly.

Additionally, these soft acrylic materials can have other undesirable properties for use in deformable IOL applications, such as tackiness and/or stickiness. For instance, surface tackiness can create handling problems by hindering deformation of the IOL to a sufficiently small size for insertion through the narrow opening of the incision. To reduce this surface tackiness of the IOLs, the addition of surface energy lowering agents or plasma treatment processes have been used. However, this additional step cannot only be costly but could also alter the properties such as the biocompatibility of this IOL.

Thus, although both the rigid PMMA IOL and deformable IOL made from silicones, hydrogels and acrylics have desirable properties they also have inherent disadvantages, which may render them unsuitable for use as an IOL. For the foregoing reasons, there is a need to provide a biocompatible, intraocular lens and lens material, which has superior optical characteristics and can be used to form a flexible intraocular lens which can be simply rolled or folded into a configuration that will fit through a small incision. These properties include a relatively high refractive index, optical clarity, and sufficient characteristics and properties to provide a flexible intraocular lens, which is adequately deformable for insertion through a small incision. Additionally, it would be advantageous to provide an intraocular lens and lens material having the aforementioned properties and for the lens to also have appropriate elasticity, elastic memory, mechanical properties and possess a non-sticky surface and/or have reduced tackiness. The present invention includes polymeric materials, which are useful in the production of deformable lenses, including but not limited to intraocular lenses (IOL's), refractive intraocular contact lenses, and standard contact lenses, the latter type being useful for correcting aphakia, myopia and hypermetropia.

Summary of the Invention

This invention is related to a novel deformable intraocular lens (IOL) and its composition derived from the copolymers of methacrylate ester monomers where the copolymer comprises either general formula I or II, wherein n = at least 1 monomer unit:

For formula I, R and R' are independently selected from the group consisting of n- alkyl, .sec-alkyl, ώo-alkyl, tert-alkyl and other isomeric alkyl radicals, substituted alkyl radicals containing oxygen and substituted alkyl radicals containing nitrogen. Preferably, R and R' are C1-C20, branched or linear alkyl radicals, wherein R' contains only aliphatic alkyls and more preferably, R= CH₃ so that one of the monomers is methylmethacrylate (MMA). For formula II, a third monomer of a different methacrylate ester (R") is included to modify the hydrophobicity of the copolymer. In formula II, third monomers include, but are not limited to, hydroxyethyl methacrylate, hydroxypropyl methacrylate, 2-aminoethyl methacrylate. Also, optionally included for both formulas I and II is a cross-linking monomer having a plurality of polymerizable ethylenically unsaturated groups, for instance ethylene glycol dimethacrylate. Still optionally, an ultraviolet absorbing material (UN absorber) with a polymerizable functional group, such as 2-[3-(2 H-benzotriazol- 2-yl)-4-hydroxyphenyl]-ethylmethacrylate is also included in the composition.

These methacrylate copolymers can be used to form intraocular lenses that have an essentially tack- free surface, a glass transition temperature (T_g) below about 37°C and more preferrably, below 20°C, a tensile strength from about 100 psi to about 1000 psi, and a refractive index from about 1.47 to about 1.49. These lenses are flexible and transparent, capable of being inserted into the eye through a relatively small incision, and recover to their original shape after insertion.

Further objects of the invention will be apparent from the description of the invention which follows.

Detailed Description

The present invention describes a biocompatible, intraocular lens and lens materials, which have superior optical characteristics and balanced physical properties. These properties include a relatively high refractive index, optical clarity, and sufficient characteristics and properties to provide a flexible intraocular lens, which is adequately deformable for insertion through a small incision. In addition to having the aforementioned properties, the intraocular lens and lens materials of this invention also have the appropriate elasticity, elastic memory, mechanical properties and possesses a non-sticky surface with reduced tackiness.

Definitions

Throughout the disclosure, unless the context clearly dictates otherwise, the terms "a" "an" and "the" include plural referents. Thus, for example, a reference to "a copolymer" includes a mixture of polymers and statistical mixtures of polymers which include different weight average molecular polymers over a range.

Unless defined otherwise, all technical terms and scientific terms used herein have the same meaning as commonly understood by one ordinarily skilled in the art to which this invention belongs. Although any methods and materials similar or equivalent to those described herein may be used in the practice or testing of the present invention, preferred methods and materials are described below. All publications mentioned herein are incorporated by reference. Further, specific terminology of particular importance to the description of the invention is defined below.

The term "biocompatible" is intended to mean that no acute physiological activity is observed in response to the presence of the material or substance described as possessing such a property. Examples of unacceptable physiological activity would include surface irritation, cellular edema, etc.

The terms "polymer," "copolymer," and "polymeric material" are used interchangeably and herein to refer to materials formed by linking atoms or molecules together in a chain to form a longer molecule, i.e., the polymer. The polymers used in the present invention are preferably biologically inert, biocompatible and non-immunogenic. The particularly preferred polymeric materials are copolymers which, are biocompatible, non-immunogenic and not subject to substantial degradation under physiological conditions. The term "glass transition temperature" (T_g) refers to the temperature at which the amorphous domains of a polymer take on the characteristic properties of the glassy state-brittleness, stiffness, and rigidity. At the glass transition temperature, the solid, glassy polymer begins to soften and flow (see Encyclopedia of Polymer Science and Engineering, 2^nd edition, vol. 7, pp. 531-544).

General Physical Characteristics for Deformable IOLs

The size and mechanical characteristics of deformable IOLs play an integral role in the effectiveness of the device. The deformable IOL should have sufficient structural strength, elasticity and elongation to allow the lens to be folded without fracturing. The IOL must also be small enough to permit adequate deformation for insertion through a small incision (less than about 3.5 mm). After insertion, the lens should regain its original shape at a controlled rate. The slow return allows the surgeon adequate time to locate the folded IOL in the eye before the lens body returns to its original shape and resolution and insures that the unfolding of the lens will not damage or otherwise traumatize surrounding ocular tissue. The IOL should also have sufficient structural integrity to retain such shape under normal use conditions. In general, the thinner the deformable IOL, the smaller the incision that is typically required. Further, in order for the IOL to function as desired after implantation, the lens must have sufficient optical refractory power. The refractive power of a lens is a function of its shape and the refractive index of the material from which it is made. A lens made from a material having a higher refractive index can be thinner and provide the same refractive power as a lens made from a material having a relatively low refractive index.

Intraocular lenses which are designed to be rolled or folded for insertion through a small incision, have a thinner cross-section and are inherently more flexible. Because of the high refractive index of the copolymers from which the flexible IOLs of this invention are made, such IOLs can be manufactured with a thinner lens made from a polymer or copolymer with a lower refractive index, such as silicone. Accordingly, the IOLs of the present invention have thinner cross- sections than known silicone IOLs, and therefore permit the use of a smaller incision. Selection of Polymeric Materials for Deformable IOLs

A primary object of this invention is to define a new soft methacrylate copolymer composition suitable for deformable IOL fabrication. It is also an object of the present invention that the polymer backbone structure of the soft methacrylate copolymer include a methyl group in order to structurally mimic the backbone of PMMA. It is a further object of this invention that the side chain ester group attached to the polymer backbone is selected to be structurally similar to a methyl group, as in other R-alkyl groups. Additionally, selection of the side chain ester group should result in a methacrylate ester copolymer which has a glass transition temperature (T_g) less than body temperature (i.e. 37°C), and preferably less than 20°C. It is still a further object of the present invention that the methacrylate ester copolymer composition of this invention be essentially tacky- free through the appropriate selection of starting co-monomers, thereby, eliminating the use of surface energy lowering agents or using a plasma surface modification process. The polymers of the present invention are prepared by generally conventional polymerization methods (see Encyclopedia of Polymer Science and Engineering, Second Edition, Volume 1, pages 265-276, John Wiley & Sons, 1985.) The methacrylate copolymer composition used for the preparation of the foldable IOLs is derived from a variety of methacrylate ester monomers comprising a general formula of:

wherein R can independently be «-alkyl, .seoalkyl, -so-alkyl, tert-alkyl, or other isomeric alkyls, or R may be substituted alkyls which contain heteroatoms, such as oxygen or nitrogen. Preferably, R is a C 1 -C20, branched or linear alkyl radical, and more preferably, one monomer of the mixture is methylmethacrylate, so that R= CH₃. Suitable monomers include, but are not limited to, methyl methacrylate, ethyl methacrylate, butyl methacrylate, hexyl methacrylate, lauryl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxylhexyl methacrylate and N,N-dimethylethyl methacrylate.

The soft, methacrylate ester copolymer composition of the present invention is preferably crosslinked with suitable crosslinkers comprising copolymerizable cross- linking monomers having a plurality of polymerizable ethylenically unsaturated groups. Suitable crosslinkers include, but are not limited to, ethylene glycol dimethacrylate, 1,3-propanediol dimethacrylate, 1 ,4-butanediol dimethacrylate, 1,6- hexanediol dimethacrylate and allyl methacrylate. The co-polymerization reaction can be induced by traditional free radical initiators, such as azobisisobutyronitrile (AIBN), benzoylperoxide, as well as other free radical initiators.

Preferably, an ultraviolet absorber with a polymerizable functional group is also included in the copolymer composition. Ultraviolet absorbers useful for IOL fabrications are, for example: 2-[3-(2 H-benzotriazol-2-yl)-4-hydroxyphenyl]ethyl- methacrylate.

Discussion

IOLs made of silicone-based polymeric materials have refractive indices which are generally about 1.46 or less. Consequently, the center or thickness of these IOLs is substantially greater than IOLs composed of materials having higher refractive indices.

Those who are skilled in the art understand that polymers of acrylate esters tend to have lower glass transition temperature (T_g), thus, these polymers can be soft and sticky (or tacky) while polymers of methacrylate esters generally tend to have higher glass transition temperature, and therefore can be hard, resulting in their inability to fold at room temperature. Typically, polymers of methacrylate esters can be less sticky or nonsticky compared to acrylate esters. Additionally, copolymers engineered from the combination of acrylate esters with methacrylate esters can have a glass transition temperature below body temperature. Therefore, IOLs made of this type of copolymer can provide flexibility so that the lens can be folded requiring a small incision. On the other hand however, such a copolymer can be sticky (or tacky), which can be an undesirable property for IOL manipulation.

It is well understood by those skilled in the art that the inherent tackiness of the acrylate/methacrylate copolymer can be caused by the presence of a low T_g acrylate in the copolymer composition. When the low T_g acrylate is removed form the copolymer composition leaving only methacrylate units, the resulting copolymer will be non-tacky but it may also inflexible, and therefore not suitable for deformable IOL materials. However, copolymer compositions of the present invention are selected from monomeric methacrylate esters wherein the combination of methacrylate ester monomers is such that the resulting copolymer material will have a T_g below 37°C. With this approach, the undesired tackiness of the IOL material is avoided while maintaining the needed flexibility of the IOL material.

Further, the selection of methacrylate esters for the present invention provides a copolymer with a refractive index in the range of about 1.47 to about 1.49. Those who are skilled in the art will appreciate the fact that a refractive index in the range of about 1.47 to about 1.49 can also be sufficient for lenses designed for cataract patients. Accordingly, for the present invention, it is therefore undesirable for the refractive indices of the copolymers to fall below about 1.46. In light of the foregoing discussion, it would be advantageous to design a new soft copolymer composition derived from monomers of methacrylate esters which overcome the shortcomings of polymers derived from PMMA or other acrylate ester- based copolymers.

Therefore, a methacrylate ester-based copolymer should provide similar desirable properties as that of PMMA since both polymers are a methacrylate ester- based polymer composition, which contain identical polymer backbone structures in terms of the incorporation of an appended methyl group off the tertiary carbon atom. The only structural alteration from PMMA is the nature of the R group(s) appended from the ester side chains of the second and possibly the third methacrylate ester monomers. This engineering principle for a new soft, methacrylate ester copolymer composition is illustrated by the following general formulas: (wherein n = at least 1 monomer unit):

Structure of PMMA

Structures of the Methacrylate Ester-based Copolymers, I, II

A copolymer of methacrylate esters can be made non-sticky if appropriately substituted monomers of the methacrylate esters are selected in such a way that the T_g of the copolymer is lower than body temperature. It would also be desirable for the first monomer of the methacrylate ester copolymer to be methyl methacrylate (MMA).

The selection of the R group in the copolymer is preferably limited to alkyl or substituted alkyl groups. In this way, the similarity in polymer structure between the soft methacrylate copolymer composition and that of PMMA can be maintained to the highest degree. Accordingly, this new soft, methacrylate ester copolymer composition has a structure which resembles as closely as possible the structure of a PMMA. Also, analogous to the PMMA lens, the biocompatibility of this new soft, methacrylate ester lens mirrors that of the PMMA lens due to the close structural similarities. However, unlike PMMA lens, IOLs made from this new methacrylate ester copolymer composition are soft so they can be easily folded thereby requiring only a small incision for insertion. Furthermore, this new soft methacrylate copolymer composition is not sticky or tacky. In addition, this methacrylate-based lens will have balanced properties of optical clarity, high refractive index, flexibility, elasticity, elastic memory, mechanic properties, and a nonsticky surface. All of these properties are required for a deformable IOL.

Examples

In order that the present invention may be more fully understood, the following examples and other comparative results are given by way of illustration only and are not intended to be limiting.

General Method: The general method for forming a biocompatible deformable intraocular lens comprises the steps of: (1) mixing suitable methacrylate esters; (2) partially polymerizing the methacrylate esters with an appropriate free radical initiator to form the pre-polymer; (3) forming a lens body with the polymer from step (2); and (4) curing the product of step (3). This process will produce a polymeric material, which has an essentially tack-free surface, a glass transition temperature (T_g) below about 37°C, a tensile strength from about 100 psi to about 1000 psi, and a refractive index from about 1.47 to about 1.49. Example 1

To a round-bottomed flask, equipped with a magnetic stirring bar, is added a mixture of 5.9 grams of MMA (methylmethacrylate), 15 grams of lauryl methacrylate, 0.07 grams of ethylene glycol dimethacrylate, and 0.02 grams of benzoyl peroxide. The flask is purged with nitrogen gas for about two minutes and subsequently maintained under positive N₂ atmosphere. The reaction mixture is then heated to about 100-110°C in a silicone oil bath with occasional stirring. After approximately 20 minutes, evolution of gas is observed, indicating decomposition of the benzoylperoxide initiator to form benzoyloxy radicals initiating the polymerization reaction. After approximately 5 minutes from when the initial gas evolution was first observed, the reaction mixture becomes obviously viscous, indicating the polymerization and crosslinking reaction has occurred. Before the mixture becomes too viscous to be poured out from the flask, the mixture is transferred to a glass plate with a Teflon gasket. A second glass plate is placed over the reaction mixture in order to sandwich the reaction mixture in between the two glass plates. The glass plates are clamped together and placed in a preheated oven at 110°C overnight (about 15 hours). The temperature is then raised to about 130°C for approximately 3 hours. The glass plates are subsequently removed from the oven and opened while still warm. A transparent, non-tacky elastic sheet (approximately 3.5 inch x 4.5 inch) is obtained.

A lens can be made in a similar manner when a stainless steel mold is used instead of the glass plate.

The mechanical properties of the resulting elastic copolymer are measured by standard ASTM test methods: tensile strength 150 psi; elongation 450%. The glass transition temperature is 0°C and refractive index is 1.48. The hardness, as measured by durometer Shore A is 20. The component composition of Example 1 is summarized in Table 1.

Table 1

*percent based on total percent of monomer

Example 2 The same procedure as in Example 1 is followed with the exception of the reactants:

7.8 g of methylmethacrylate is combined with 13.2 g of lauryl methacrylate, 0.02 grams of benzoyl peroxide, and 0.07 g of the crosslinker ethylene glycol dimethacrylate, is also added to the reaction mixture. The co-polymerization is initiated by benzoyl peroxide. The component composition is summarized in Table 2. The mechanical properties of the resulting elastic copolymer are: tensile strength: 550 psi; elongation %: 488%; T_g: 9°C; Refractive index: 1.484; hardness (Shore A): 33.

Table 2

Example 3

The same procedure as in Example 1 is followed with the exception of the reactants: 10.3 g of methylmethacrylate is combined with 9.2 g of lauryl methacrylate, 0.02 grams of benzoyl peroxide and 0.07 g of the crosslinker ethylene glycol dimethacrylate, is also added to the reaction mixture. The co-polymerization is initiated by benzoyl peroxide. The component composition is summarized in Table 3. The mechanical properties of the resulting elastic copolymer are: refractive index: 1.486; glass transition temperature (T_g): 28°C; hardness (Shore A): 88.

Table 3

Example 4

The same procedure as in Example 1 is followed with the exception of the reactants: 7.8 g of methylmethacrylate is combined with 13.2 g of lauryl methacrylate, 0.02 grams of benzoyl peroxide, 0.2 g of the crosslinker ethylene glycol dimethacrylate, and 0.3 g 2-[3-(2 H-benzotriazol-2-yl)-4-hydroxyphenyl]ethyl methacrylate, as a UN absorber. The co-polymerization is initiated by benzoyl peroxide. Table 4 summarizes the composition. The elastic copolymer has the following properties: refractive index: 1.485; tensile strength: 725psi; elongation 324%; hardness (Shore A): 46; T_g: 9°C. Table 4

ylmethacrylate

Example 5

The same procedure as in Example 1 is followed with the exception of the reactants: 4.8 g of methylmethacrylate is combined with 15.2 g of hexyl methacrylate, 0.02 grams of benzoyl peroxide, and 0.07 g of the crosslinker ethylene glycol dimethacrylate. The co-polymerization is initiated by benzoyl peroxide. Table 5 summarizes the composition. The elastic copolymer has the following properties: refractive index: 1.482; Durometer (Shore A): 47; glass transition temperature: 23°C; tensile strength: 579 psi; elongation: 444%.

Table 5

Example 6

The same procedure as in Example 1 is followed with the exception of the reactants: 8.8 g of methylmethacrylate is combined with 15 g of lauryl methacrylate. and 0.02 grams of benzoyl peroxide. A transparent, non-sticky rubbery material is formed. However, when using this composition, glass plates cannot be used due to strong adhesion between the resulting copolymer and the glass surface. This adhesion problem can be resolved by using Teflon plates instead of glass plates. Table 6 summarizes the composition.

Table 6

Those who are skilled in the art will understand that the present invention through the preceding exemplary embodiments lays the foundation for numerous altςmatives and modifications thereto. For example, it may be possible to select or custom-design a first acrylate of special structure that has a similar property to PMMA and a second acrylate similar to lauryl methacrylate. Those skilled in the art will also understand that the compositions given in the above examples, particularly the one in Example 4, have desirable properties for IOLs. Conventional methods of compression mold or lathe machining can be utilized to fabricate IOLs. Although the present invention has been described in considerable detail with reference to certain preferred versions, other versions are possible.

Claims

What is claimed is:

1) A deformable intraolcular lens (IOL) comprising a biocompatible polymeric acrylate material comprising copolymers of methacrylate esters wherein the acrylic material has: a) a glass transition temperature (T_g) below about 37°C; b) a tensile strength from about 100 psi to about 1000 psi; and c) a refractive index from about 1.47 to about 1.49.

2) The IOL of claim 1 wherein the polymeric acrylate material is comprised of two monomeric units having the formula:

wherein R and R' are independently selected from the group consisting of w-alkyl,

.sec-alkyl, wσ-alkyl, tert-alkyl, other isomeric alkyl radicals, substituted alkyl radicals containing oxygen and substituted alkyl radicals containing nitrogen.

3) The IOL of claim 2 wherein R and R' are independently C1-C20 linear and branched alkyl radicals. 4) The IOL of claim 3 wherein R is a -CH₃ radical.

5) The IOL of claim 4 wherein R' is a C-18 linear alkyl radical.

6) The IOL of claim 3 further comprising a copolymerizable cross-linking monomer having a plurality of polymerizable ethylenically unsaturated groups.

7) The IOL of claim 6 wherein the crosslinking monomer is ethylene glycol dimethacrylate.

8) The IOL of claim 6 further comprising an ultraviolet absorbing material with a polymerizable functional group.

9) The IOL of claim 8 wherein the ultraviolet absorbing material is 2-[3-(2 H- benzotriazol-2-yl)-4-hydroxyphenyl]-ethylmethacrylate.

10) The IOL of claim 1 wherein the polymeric acrylic material is comprised of three monomeric units having the formula:

wherein R and R' are independently selected from the group consisting of «-alkyl. sec-alkyl, wo-alkyl, tert-alkyl and other isomeric alkyl radicals, substituted alkyl radicals containing oxygen and substituted alkyl radicals containing nitrogen; and R" is a group which modifies the hydrophobicity of the said material.

11) The IOL of claim 10 wherein R and R' are independently C1-C20 linear and branched alkyl radicals.

12) The IOL of claim 11 wherein R is a -CH₃ radical.

13) The IOL of claim 12 wherein R' is a C-18 linear alkyl radical.

14) The IOL of claim 11 wherein R" is selected from the group consisting of hydroxyethyl, hydroxypropyl and 2-aminoethyl radicals.

15) The IOL of claim 14 further comprising a copolymerizable cross-linking monomer having a plurality of polymerizable ethylenically unsaturated groups.

16) The IOL of claim 15 wherein the crosslinking monomer is ethylene glycol dimethacrylate.

17) The IOL of claim 15 further comprising an ultraviolet absorbing material with a polymerizable functional group.

18) The IOL of claim 17 wherein the ultraviolet absorbing material is 2-[3-(2 H- benzotriazol-2-yl)-4-hydroxyphenyl]-ethylmethacrylate.

19) A deformable intraolcular lens material formed by polymerizing methacrylate esters to produce a biocompatible polymeric reaction product comprising copolymers of methacrylate esters wherein the reaction product: a) has a glass transition temperature (T_g) below about 37°C; b) has a tensile strength between about 100 psi and 1000 psi; and c) has a refractive index from about 1.47 to about 1.49.

20) The material of claim 19 wherein the reaction product is comprised of two monomeric units having the formula:

wherein R and R' are independently selected from the group consisting of w-alkyl, seoalkyl, iso-alkyl, tert-alkyl and other isomeric alkyl radicals, substituted alkyl radicals containing oxygen and substituted alkyl radicals containing nitrogen. 21) The material of claim 20 wherein R and R' are independently C1-C20 linear and branched alkyl radicals.

22) The material of claim 21 wherein R is a -CH₃ radical.

23) The material of claim 22 wherein R' is a C-18 linear alkyl radical.

24) The material of claim 21 wherein the reaction product further comprises a copolymerizable cross-linking monomer having a plurality of polymerizable ethylenically unsaturated groups.

25) The material of claim 24 wherein the crosslinking monomer is ethylene glycol dimethacrylate.

26) The material of claim 24 wherein the reaction product further comprises an ultraviolet absorbing material with a polymerizable functional group.

27) The material of claim 26 wherein the ultraviolet absorbing material is 2-[3-(2 H- benzotriazol-2-yl)-4-hydroxyphenyl]-ethylmethacrylate. 28) The material of claim 19 wherein the reaction product is comprised of three monomeric units having the formula:

wherein R and R' are independently selected from the group consisting of n-alkyl, sec-alkyl, /-?o-alkyl, tert-alkyl and other isomeric alkyl radicals, substituted alkyl radicals containing oxygen and substituted alkyl radicals containing nitrogen; and R" is a group which modifies the hydrophobicity of the said composition.

29) The material of claim 28 wherein R and R' are independently C1-C20 linear and branched alkyl radicals.

30) The material of claim 29 wherein R is a -CH₃ radical.

31) The material of claim 30 wherein R' is a C-18 linear alkyl radical.

32) The material of claim 29 wherein R" is selected from the group consisting of hydroxyethyl, hydroxypropyl and 2-aminoethyl radicals.

33) The material of claim 32 wherein the reaction product further comprises a copolymerizable cross-linking monomer having a plurality of polymerizable ethylenically unsaturated groups.

34) The material of claim 33 wherein the crosslinking monomer is ethylene glycol dimethacrylate.

35) The material of claim 33 wherein the reaction product further comprises an ultraviolet absorbing material with a polymerizable functional group.

36) The material of claim 35 wherein the ultraviolet absorbing material is 2-[3-(2 H- benzotriazol-2-yl)-4-hydroxyphenyl]-ethylmethacrylate.

37) A method for forming a biocompatible deformable intraocular lens comprising the steps of: a) mixing suitable methacrylate esters that will produce a polymeric material which has: i) a glass transition temperature (T_g) below about 37°C; ii) a tensile strength below from about 100 psi to about 1000 psi; and iii) a refractive index from about 1.47 to about 1.49; b) partially polymerizing the methacrylate esters of step a) to form the pre- polymer; c) forming a lens body with the product of step b); and d) curing the product of step c).

38) The method of claim 37 wherein the polymeric material has the general formula: wherein R is a -CH₃ radical and R' is a C-l 8 linear alkyl radical.

39) The method of claim 38 wherein the polymeric material is chemically crosslinked with ethylene glycol dimethacrylate.

40) The method of claim 39 wherein the polymeric material further comprises the ultraviolet absorbing material is 2-[3-(2 H-benzotriazol-2-yl)-4-hydroxyphenyl]- ethylmethacrylate.

41) The method of claim 37 wherein the polymeric material has the general formula:

wherein R is a -CH₃ radical, R' is a C-18 linear alkyl radical, and R" is selected from the group consisting of hydroxyethyl, hydroxypropyl and 2-aminoethyl radicals.

42) The method of claim 40 wherein the polymeric material is chemically crosslinked with ethylene glycol dimethacrylate.

43) The method of claim 42 wherein the polymeric material further comprises the ultraviolet absorbing material 2-[3-(2 H-benzotriazol-2-yl)-4-hydroxyphenyl]- ethylmethacrylate.