Manufacturing of positive power opthalmic lens

Abstract From the Canadian patent

Multifocal ophthalmic lenses may be manufactured by either injection molding and casting methodologies. The use of two opposed tools (mold faces) with relatively, centered faces, but with significantly differing diameters can be used to provide, multifocal ophthalmic lenses. The process is surprisingly capable of providing multifocal lenses with good control of the thickness of the lenses with , relatively thin, center thicknesses (e.g. less than 4.7 mm or less than 3.5 mm) and , relatively thin edge thicknesses (e.g. 0.5 to 2.5 or to 2.0 mm). The tool faces (the molds for the, front and rear surfaces) may be readily replaced within the mold to enable manufacture of a wide range of lens …