Bifocal contact lens

Abstract

A bifocal contact lens is formed from a material having a uniform index of refraction and includes a concave posterior surface shaped in conformity with a patient's cornea and defining a lens optical axis. The bifocal contact lens includes two separate vision correction surfaces on the anterior side of the lens. A convex distance correction surface has a distance correction radius of curvature with its center of curvature at a point on a line extending parallel to, or coinciding with, the optical axis of the lens. A convex near correction anterior surface has a near correction radius of curvature with its center of curvature at a point also on the line extending parallel to, or coinciding with, the lens optical axis. The junction between the distance correction surface and the near correction surface has an upwardly opening crescent shape and comprises a step or ledge out from the distance correction surface. A method of producing the anterior surfaces for the bifocal contact lens comprises fixing a lens blank on a lathe spindle with the lens blank axis intersecting and forming an acute angle to the lathe spindle rotational axis, rotating the lens blank about the spindle rotational axis, and then cutting both the convex distance correction surface and the convex near correction surface.

Dependencies are inferred from the claim text.