Patent ID: 6199982
Filing Date: 2001-03-13
Classification: G02C

Abstract:
A presbyopia correction contact lens including an optical zone which consists of a substantially circular central optical portion and an annular peripheral optical portion which is radially outwardly of said central optical portion, said central and peripheral optical portions having respectively determined mutually different optical power values, so that said central and peripheral optical portions provide one and the other of a near vision correction region and a distant vision correction region, respectively, wherein the improvement comprises:said central optical portion providing said near vision correction region while said peripheral optical portion provides said distant vision correction region, said optical zone including a front surface having a generally arcuate configuration with a substantially constant degree of curvature in cross section taken in a plane parallel to a diametric direction of said contact lens, and a back surface consisting of a central portion corresponding to said central optical portion and a peripheral portion corresponding to said peripheral optical portion, said central portion of said back surface having a generally arcuate configuration with a substantially constant degree of curvature in cross section taken in said plane, which curvature is made smaller in all diametric directions of said contact lens than that of said peripheral portion of said back surface, said back surface of said optical zone being formed so as to be spaced apart from a corneal surface of an eye of a lens user at and in the vicinity of a boundary between said central and peripheral optical portions, so as to form a clearance between said back surface and the corneal surface, which clearance has a predetermined radial width corresponding to adjacent radial end sections of said central and peripheral optical portions.