OXYGEN PERMEABLE CONTACT LENS AND METHOD OF MANUFACTURE THEREFOR

摘要

An oxygen permeable bifocal contact lens which has a distance vision portion and a near vision portion is made from materials having differing refractive indexes. The near vision portion has a higher refractive index than the distance portion with a Dk of at least 10. The distance portion forms the major portion of the lens and is formed as a crosslinked copolymer with a refractive index of not more than 1.49 from monomeric materials which impart oxygen permeability to the finished lens, and the near vision portion similarly is formed as a crosslinked copolymer from a monomer mixture which includes one or more monomers at a concentration and with a refractive index such that the near vision portion has a refractive index of at least 1.54. The monomer of the near vision portion includes at least one vinyl monomer having a substituted aromatic ring structure to make the monomer bulky and ensure there is only a limited shrinkage on polymerization of such monomers and mixtures containing them.