Water plasticized high refractive index polymer for...

Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...

Reexamination Certificate

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C526S320000, C526S323000, C526S323200, C526S326000, C526S327000, C526S328500, C526S346000, C526S347000, C623S006110, C623S006120, C623S006580

Reexamination Certificate

active

06635731

ABSTRACT:

BACKGROUND OF INVENTION
This invention relates to copolymer materials which are useful as ophthalmic devices, such as contact lenses, intraocular lenses (IOLs), keratoprostheses, and corneal rings or inlays, and a process for making and using such copolymer materials. In particular, this invention relates to intraocular foldable lenses formed from acrylic copolymer materials.
With recent advances in small-incision cataract surgery, increased emphasis has been placed on developing soft, foldable materials suitable for use in artificial ophthalmic lenses. In general, these materials fall into one of three categories: hydrogels, silicones, and generally, others.
The refractive power of a lens is a function of its shape and the refractive index of the material of 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 lower refractive index. Thinner lenses are easier to insert and cause less trauma during surgery.
Hydrogel materials are hard or rigid when dry, and absorb a large amount of water (e.g., up to 20-70% by weight) when hydrated, which lowers the refractive index of the material. These materials tend to be brittle when dry, and have poor mechanical properties for ophthalmic applications. In a hydrated state, hydrogel materials become soft and pliable. Known hydrated hydrogels have a relatively low refractive index, for example, less than 1.48. In addition to adversely affecting the refractive index, the absorbed water also significantly increases the diameter and thickness of the IOLs, for example, by as much as about 15 percent.
Silicone materials have a slightly higher refractive index (for example, 1.51), but tend to unfold too rapidly after being placed in the eye in a folded configuration. The biocompatibility of silicone materials may also be a concern.
U.S. Pat. No. 5,290,892 (Namdaran et al.), U.S. Pat. No. 5,331.073 (Weinschenk, III et al.), and U.S. Pat. No. 5,693,095 (Freeman et at.), the complete disclosures of which are hereby incorporated by reference, discuss forming foldable lenses out of a polymer material derived from an ethoxyaryl (meth)acrylate with a crosslinker or with a second acrylate monomer and crosslinker. Since the polymer material is soft/foldable, those patents discuss mold forming the polymer material to individually form the lens. Likewise, U.S. Pat. No. 5,433,746 to Namdaran et al., which is herein fully incorporated by reference, discloses forming flexible intraocular lenses by molding polymeric materials which have a relatively low glass transition temperature. Such molding requires specialized equipment and expensive customized molds. In addition, the resulting molded lenses tend to have poor surface quality since they generally cannot be polished. Alternatively, U.S. Pat. No. 5,331,073 discusses forming lenses from a soft foldable material by machining the lenses at cryogenic temperatures. Such a process is cumbersome and expensive.
A foldable, high refractive index material, which may be machined and polished using conventional technology, would be a significant advancement in the art.
SUMMARY OF THE INVENTION
The present invention provides a foldable, high refractive index material which may be machined using inexpensive conventional lathe cutting techniques, such as those used in the manufacture of polymethyl methacrylate (PMMA) lenses. The polymeric materials are useful for forming ophthalmic devices, particularly intraocular lenses, comprising polymer units derived from at least three different monomeric components. The resulting polymeric materials are also useful for other ophthalmic devices, such as contact lenses, keratoprostheses, intracorneal lenses (ICL), and corneal rings or inlays, as well as for other applications.
A significant novel aspect of polymeric material of the invention is that it both (a) is hard enough to machine at room temperature, and (b) may be rendered foldable through a controlled hydrating process. Further, the IOL may be hydrated to a suitably flexible state with minimal water uptake. The relatively low water uptake allows efficient hydration without affecting mechanical or optical properties and without changing the dimensions or the refractive index of the foldable lens. Another major advantage of the invention is the ability to tumble polish the lenses to provide smooth and rounded edges. This is facilitated, in part, by the relatively high glass transition temperature (Tg) of the material.
One aspect of the present invention is a composition comprising a hydratable copolymer. The copolymer includes:
a) a first monomeric component which is an aryl acrylate or an aryl methacrylate;
b) a second monomeric component which is a monomer having an aromatic ring with a substituent having at least one site of ethylenic unsaturation, wherein the second monomeric component is other than an acrylate; and
c) a third monomeric component which is a high water content hydrogel-forming monomer. Preferably, the copolymer further includes a crosslinking agent.
Another aspect of the invention is an ophthalmic device made from the copolymer of the invention.
The invention also provides a process for making ophthalmic devices such as intraocular lenses from the polymer(s) disclosed. The process generally involves forming a rigid polymer work piece from the copolymer of the invention, forming an ophthalmic device from the work piece, and hydrating the ophthalmic device to a sufficiently soft and flexible state so that, if desired, the device can be folded.
A further aspect of the invention is a method of implanting an ophthalmic device within an eye. The method involves providing a hydratable ophthalmic device which is rigid at room temperature when dry, and foldable at room temperature when hydrated. The ophthalmic device is hydrated and a syringe is provided which contains the hydrated ophthalmic device. The ophthalmic device is then injected into the eye.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The polymer material of the present invention comprises polymer units derived from the polymerization of first, second, and third monomeric components. These components may include aryl (meth)acrylate monomer, an aromatic monomer, and a high water content hydrogel-forming monomer, respectively. Preferably a crosslinking agent is included. Each of the components is described below in more detail.
The composition may optionally include other monomeric components, an initiator, or an ultraviolet (UV) absorbing material. The proportions of the monomers should preferably be chosen to produce a substantially rigid polymer having a glass transition temperature of at least about normal room temperature. Each of the three different monomeric components is preferably present in the copolymer in an amount of at least about 10 weight percent, more preferably, at least about 20 weight percent. This invention contemplates preparation of random and block copolymers of the monomeric components discussed herein. Unless otherwise stated, all weight percents are based on the total weight of the composition prior to polymerization.
In a highly preferred embodiment, the composition comprises a hydratable copolymer which includes:
a) at least about 20 weight percent of a first monomeric component such as ethylene glycol phenyl ether acrylate or polyethylene glycol phenyl ether acrylate;
b) at least about 10 weight percent of a second monomeric component such as styrene or substituted styrene;
c) at least about 10 weight percent of a third monomeric component such as hydroxy ethyl methacrylate, hydroxyethoxy ethyl methacrylate, or methacrylic acid; and
d) less than about 10 weight percent of a crosslinking agent such as a diacrylate or a dimethacrylate. The resulting copolymer has a refractive index greater than about 1.50 and is foldable at normal room temperature (that is, about 20-25° C.) when hydrated.
Monomers
Generally, the first monomeric component is an aryl acrylate or an aryl methacrylate. These compounds may als

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