Method for preparing a crosslinked graft copolymer of silicone and polyvinylpyrrolidone for use as a contact lens, and a contact lens produced thereby
AssigneeEssilor International (Compagnie Generale d'Optique)
InventorsGeorges Wajs, William Lenne
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Abstract
An improved flexible contact lens is provided having hydrophilic and lipophobic properties which allow extended duration of wear by eliminating or greatly reducing the risk of rupture of the natural tear film produced by the cornea. These properties are achieved by crosslinking a selected water soluble polymer which has been grafted onto a pre-formed substrate, for example crosslinking polyvinyl pyrrolidone which has been previously grafted onto a silicone substrate. The grafting and the crosslinking are accomplished in separate stages.
Claims8
A method for preparing a contact lens adapted to be worn on the cornea comprising preparing a substrate of generally concavo-convex shape, said substrate consisting essentially of a graft copolymer of about 75 to 99% by weight of a polyorganosiloxane having about 1 to 25% by weight of polyvinylpyrrolidone grafted thereto;
- and irradiating said substrate to crosslink said polyvinylpyrrolidone units, said irradiating being of sufficient intensity and duration to cause a sufficient amount of crosslinking of said polyvinylpyrrolidone units to substantially reduce the risk of rupture of a pre-corneal lachrymal film, while said graft copolymer remains capable of being rendered transparent and has the optical properties necessary to function as a contact lens.
A contact lens of generally concavo-convex shape adapted to be worn on the cornea produced by the method comprising the steps of preparing a substrate of generally concavo-convex shape, said substrate consisting essentially of a graft copolymer of about 75 to 99% by weight of a polyorganosiloxane having about 1 to 25% by weight of polyvinylpyrrolidone grafted thereto;
- and irradiating said substrate to crosslink said polyvinylpyrrolidone units, said irradiating being of sufficient intensity and duration to cause a sufficient amount of crosslinking of said polyvinylpyrrolidone units to substantially reduce the risk of rupture of a pre-corneal lachrymal film, while said graft copolymer remains capable of being rendered transparent and has the optical properties necessary to function as a contact lens.
Dependencies are inferred from the claim text.