US Patent 7810925 Bifocal contact lens

A contact lens having near vision and distance vision portions, the lens being movable on the eye between first and second positions, those positions corresponding with aligning the wearer's vision through the near vision and distance vision portions respectively. The lens is positionally stable on the eye in each of the two positions, and requires a force to be applied to the lens to move between the first and second positions. Preferably the lens has a back surface and a front surface, and said back surface has either one or two major back curve zones occupying a major portion of the lens back surface.