Multifocal contact lens with a difference power on the back surface

摘要

Disclosed is a multifocal contact lens having a first optical power on a portion of the optical region of the back surface of the lens, a second optical power on another portion of the optical region of the back surface portion of the lens, and a third optical power over the entire optical region of the front surface of the lens. The first optical power, in combination with the third optical power produces a basic, distance corrective optical power while the second optical power, more positive than the first, produces in combination with the third optical power a difference corrective power to provide the appropriate near focal length for an individual requiring bifocals. This type of bifocal contact lens can be readily manufactured by molding with a convex mold surface containing the inverse of the first and second optical powers selected for the back surface of the lens and a concave mold piece containing the inverse of the third optical power selected for the front surface of the lens.