Method for making colored photochromic prescription ophthalmic lenses

Claim 1

A process for providing a colored photochromic prescription ophthalmic lens which comprises the steps of: (a) providing a photochromic glass cap blank for a thin lens cap element to be provided with a convex front surface and a concave back surface; (b) finishing the back surface of the cap blank to a standard base curvature in the range of about 2 to 10 diopters to provide a semifinished cap blank with a concave back surface; (c) subjecting the semifinished cap blank to a heat treatment in a reducing atmosphere to cause the reduction of selected metallic constituents therein and the formation of an integral colored layer on the surfaces of the blank; (d) finishing the front surface of the cap blank to generate a front surface curvature matching the standard base curvature of the back surface, to remove front surface color, and to provide a finished cap element having a thickness not exceeding about 1.5 mm and having a convex front surface and a concave back surface; (e) providing a glass base element for the lens, said base element having a convex front surface with a standard base curvature matching that of the back surface of the finished cap element, and having a prescription-finished back surface imparting selected elements of power, cylinder, multifocal and prism correction to the base element; and (f) cementing the back surface of the colored cap element to the front surface of the base element such that the standard base curvatures mate, to provide a finished tinted prescription ophthalmic lens.