OXYGEN PERMEABLE TWO FOCUS CONTACT LENS AND METHOD OF ITS MANUFACTURE

摘要

PURPOSE: To cost effectively produce a bifocal contact lens which makes it possible to obtain a sharp visual field in both near and far sight and has oxygen permeability and the resistance to protein deposition. CONSTITUTION: The far sight part and near sight part of this bifocal contact lens consist of materials having different refractive indices. This far sight part has Dk of at least 10×10<-11> and the near sight part has the refractive index higher than the refractive index thereof. The far sight part is formed as a crosslinking copolymer having a refractive index of <=1.49 from a monomer material including a monomer which imparts oxygen permeability to the lens. The near sight part is similarly formed as the copolymer from a monomer mixture. The vinyl monomer having a substd. arom. cyclic structure is included in the monomer of the near sight part. This vinyl monomer makes the monomer bulky and assures only the limited shrinkage at the time of polymerizing the monomer and the mixture contg. the monomer.