Method of manufacturing an implantable intraocular planar/convex, biconvex, planar/concave or convex/concave lens and a lens made using this method

#The invention addresses a method of manufacture of an implantable intraocular planar/convex, biconvex, planar/concave or convex/concave lens, an open mold used for the execution of this method, and a lens made using this method.

#Intraocular lenses are lenses implantable into the eye for the purpose of the change of correction. They can be implanted into various parts of the eye, such as the posterior chamber, anterior chamber, or stroma. Intraocular lenses are made of material of various rigidity. In case of hard materials, such as certain poly(alkylmethacrylate)s, especially polymethylmethacrylate, or dehydrated hydrogels, also called xerogels, the most common manufacturing process is lathe machining with subsequent polishing. Soft intraocular lenses are usually made by casting in appropriate molds. Casting is based on filling the mold with a liquid polymer precursor, such as for instance a mixture of specific monomers, a melted polymer, or a liquid pre-polymer with a cross-linking capability, and on the subsequent conversion of this material into a solid state, known as solidification. In case of soft materials for intraocular lenses, this solidification generally includes cross-linking, i.e. the formation of a three-dimensional covalent network, which stabilizes the shape of the lens. For example, this network can be formed by either the copolymerization of bi-functional monomers with multi-functional cross-linking co-monomers, known as cross-linking agents or cross-linkers, or the additional cross-linking of the liquid polymer.

#The transition from a liquid to a solid state is accompanied by a greater or lesser volumetric contraction, which greatly complicates the casting of the product, for which a great shape accuracy is required, such as in case of intraocular lenses.

#In the drawings

#FIG. 1 is a preferred cross-section of the mold according to the invention, whose cavity is formed by a combination of an open concave cavity and a transitional open cylindrical cavity;

#FIG. 2 is a partial cross-section of another preferred open mold according to the invention, whose cavity is formed by the combination of an open concave cavity and a transitional open frustum-of-a-cone cavity;

#According to the invention, intraocular lenses can be made according to the invention from various cross-linked polymers. Within the scope of the invention, advantageous polymers are such, whose temperature of softening while in an equilibrium state with intraocular fluids is lower than the body temperature. Such polymers can be based on silicones, for example such as are described in U.S. Pat. No. 5,519,070. Further, those polymers can be hydrophobic and hydrophilic acrylic or methacrylic polymers, polyurethanes or polyureas, which are described in U.S. Pat. No. 6,165,408. Especially advantageous are hydrogels suitable for ophthalmic uses, which are, for instance, described in U.S. Pat. Nos. 2,976,576, 3,220,960, 5,224,957, 4,775,731, 4,994,083, 4,997,441, 5,002,570, 5,158,832, 5, 270, 415, 5,910,519, 5,698,636, 5,391,669, 5,674,283, 5,158,832 and 6,372,815. Of these, especially appropriate are the covalently cross-linked copolymers containing acrylic and/or methalcrylic acid and their derivatives, such as esters, amides, or salts. The most suitable are cross-linked copolymers of hydrophilic methacrylates.

#At least a part of a copolymer is formed by a copolymerizable monomer able to absorb radiation of a wavelengths between 290 and 500 nanometers, preferentially between 300 and 400 nanometers. Such monomers, based for example on the derivates of benzophenone or benz-triazole are well known to experts in the field. An example are copolymers absorbing ultraviolet radiation described in U.S. Pat. No. 5,133,745.

#Solidification of the liquid precursor can be accomplished by the polymerization of a mixture of basic and cross-linking monomers. Suitably, such polymerization is a radical polymerization and is initiated by either the usual free-radial initiators or by a photoinitiation mechanism. Radical polymerization can be initiated by electromagnetic radiation in various areas of the spectrum, for example in the visible radiation area, ultraviolet radiation, x-rays, or gamma radiation. Free radicals can potentially be created even by absorbance of free electrons from beta-radiation or electrons accelerated using an electrical field. Solidification can also be performed by cross-linking by liquid polymer precursors, for instance such as reactive silicone pre-polymers or polyvinylalcohol solutions. Photo-initiated polymerization or cross-linking are especially advantageous methods, and are described, for example, in U.S. Pat. Nos. 6,190,603 and 5,224,597. It is desirable that the metering of the liquid precursor is performed with the accuracy better than 1 mg, and preferably with accuracy better than 0.1 mg. The rotation of the open mold, containing the liquid polymer precursor, can be implemented using various techniques and while using various equipment, which are described in U.S. Pat. Nos. 3,660,545, 4,517,138, 4,517,139, 4,517,140 and 4,551,086. If certain components of the precursor polymer mixture are relatively volatile, it is possible to limit evaporation by keeping the mold with the liquid precursor in an enclosed system with a very small space for the gas phase while undergoing solidification. Such methods and equipment suitable for rotary casting of lenses made from volatile monomers are described in U.S. Pat. No. 4,680,149.