High refractive index polymers for ophthalmic applications

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of the priority of provisional application Ser. No. 60/552,548 filed Mar. 12, 2004 which is incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

This invention relates to novel copolymers preferably for intraocular lenses (“IOL”), contact lens, and other ophthalmic and optical applications.

SUMMARY OF THE INVENTION

This invention, in one aspect, relates to copolymer compositions comprising limited amounts of a monomer having a naphthyl moiety or naphthyl functionalities, naphthalene, or a naphthyl group. Naphthyl moiety monomers are added to the comonomer to increase the refractive index of the comonomer and to increase the ability of the copolymer material to block blue light (wavelength up to 475 nm). IOLs made from the materials of this invention have very high refractive index, and may be machined at around room temperature. IOLs of this invention may be folded and used to replace a defective natural lens of the eye by insertion of the IOL through a small incision without the need for further processing or hydration. A particular advantage of the materials of this invention, especially when used for ophthalmic applications, is their ability to block blue light, believed to be harmful to the retina, without the need for inclusion of additional dyes or pigments and without interfering with a user's color perception.

The compositions comprise copolymers of monomers including: an aryl acrylate first monomer, a homopolymer of the aryl acrylate first monomer having a refractive index of at least about 1.5, the first monomer being present in the copolymer in an amount of at least about 50 weight percent, preferably about 70-90 weight %. The composition further includes a second monomer containing a naphthyl moiety, the naphthyl moeity monomer being present in the composition at a concentration of at least 10% and preferably up to about 60%. The composition then includes a crosslinking monomer, the crosslinking monomer being present at a concentration in the range up to 10 weight percent, preferably of about 1 weight % to about 8 weight %. One skilled in the art will appreciate that the weight percentages of the classes of monomers, including any additional added monomers, processing agents, additions, etc., will equal 100 weight percent.

The copolymers polymerized from the monomers stated above are rigid enough to be machined at around room temperature. A unique aspect of the copolymers of this invention is that their refractive indices are so high that lenses can be made thin enough to be folded without further processing or hydration.

Another unique aspect of the compositions of the present invention is their ability to block harmful blue light (475 nm) without the need for additional UV inhibitors, dyes, or pigments in the copolymer.

A method of this invention includes producing a copolymer material in a convenient rod configuration by copolymerizing the above mentioned monomers using radical polymerization. Blanks in the form of disks are cut from the rod and lathe cut into lenses. One skilled in the art will be generally familiar with these steps. Lathing operations are performed at temperatures approximately room temperature. Due to the unique combination of high refractive index and mechanical properties, lenses made from these materials are thin enough (i.e., they have a thickness in the range of about 0.2 mm to about 0.7 mm) to be folded without breakage.

Preparation of Copolymer Rods

The monomers are mixed in a glass flask using a magnetic stir bar, at room temperature, 15° C., for at least 20 minutes. A total of 20 g of the comonomer mixture is used to prepare a 6-inch rod. A radical polymerization initiator trade named Vazo is added at a concentration of 0.1% and the mixture stirred for an additional 20 minutes. The comonomer solution is filtered through a 0.2 micron filter, poured into a glass tube, and then vacuum/argon degassed for 5 minutes. The test tubes are placed in a water bath at 55 degrees C. for 12 hours and then cured in an oven at 70 degrees C. for an additional 12 hours. The copolymer rods are removed from the glass test tubes and stored until use.

IOL Lathe Cutting

Blanks with a 15 mm diameter and a 2 mm thickness are cut from the polymer rod and lathed into a lens optic with diopters ranging from 4 to 40. These lenses have good optical properties including clarity, visible light transmission, and resolution. The lenses can easily be folded using forceps or conventional IOL injectors without breakage. The lenses unfold slowly and controllably in the eye without damaging surrounding tissue. They also do not exhibit any substantial “memory” returning to their unfolded configuration.

Preferred aryl acrylate monomers for use in the present invention include 2-phenyl ethyl acrylate (PEA) and benzyl acrylate (BA). Other aryl acrylate monomers include aryl (meth)acrylate monomers such as, for example: ethylene glycol phenyl ether acrylate (EGPEA), poly(ethylene glycol phenyl ether acrylate) (polyEGPEA), phenyl methacrylate, 2-ethylphenoxy methacrylate, 2-ethylphenoxy acrylate, hexylphenoxy methacrylate, hexylphenoxy acrylate, benzyl methacrylate, 2-phenylethyl methacrylate, 4-methylphenyl methacrylate, 4-methylbenzyl methacrylate, 2-2-methyphenylethyl methacrylate, 2-3-methylphenylethyl methacrylate, 2-4-methylphenylethyl methacrylate, 2-(4-propylphenyl)ethyl methacrylate, 2-(4-(1-methylethyl)pheny)ethyl methacrylate, 2-(4-methoxyphenyl)ethylmethacrylate, 2-(4-cyclohexylpheny)ethyl methacrylate, 2-(2-chlorophenyl)ethyl methacrylate, 2-(3-chlorophenyl)ethyl methacrylate, 2-(4-chlorophenyl)ethyl methacrylate, 2-(4-bromophenyl)ethyl methacrylate, 2-(3-phenylphenyl)ethyl methacrylate, 2-(4-phenylphenyl)ethyl methacrylate), 2-(4-benzylphenyl)ethyl methacrylate, and the like, including the corresponding methacrylates and acrylates, and including mixtures thereof. Other aryl acrylate monomers and aryl methacrylate monomers are likely to occur to one skilled in this art in light of the present disclosure.

A preferred naphthyl moieties or naphthalene derivatives includes 2-vinyl naphthylene 2-VN. Other naphthalene moieties include naphthyl acrylate, naphthylmethacrylate. A preferred crosslinker for use in the present invention is ethylene glycol dimethacrylate EGDM. One skilled in this art will appreciate that there are numerous other cross-linking monomers which are likely to be successfully used herein.

EXAMPLES 1-6

Using the general method described above, the following 6 comonomers were used to prepare copolymers.

The copolymer rods of Examples 1-6 were lathe cut into discs approximately the size of an IOL optic i.e., about 15 mm in diameter. The refractive indices of the discs (RI) were determined and are shown in the table. The thicknesses of the optic discs also were measured and are listed in the table. As a comparison, the highest refractive index material available is that of Acrysof lens (1.55). The thickness of a 20D Acrysof lens is 0.8 mm. which makes a substantial difference in incision size.

EXAMPLE 7

IOLs made from materials of the present invention are stored in a dry state in a sterile tray. Employing the copolymer of the invention, cataract surgery may be carried out through an incision of 2.0 mm or less. After applying topical anesthesia to the eye, an IOL made of the new copolymer materials may be injected into the eye using an inserter or a folding device.

The IOL will unfold slowly to allow the surgeon to optimize placement. The IOL will unfold completely within 30 seconds to 1 minute. The memory of the materials of the present invention are such that the IOL recovers all optical and physical properties upon unfolding.