Abstract: A method of producing a blank for the primary member of a glass mould in which an organic polymer, multifocal, ophthalmic lens is cast. A glass major element is formed that has a raised countersink zone on one surface, the remainder of the glass major element being thinner than the countersink zone, but of such thickness that it can form the far vision surface of a mould. A countersink is formed in the countersink zone and a segment element is formed and fused in the countersink. This forms a lens mould assembly which, when ground and polished to the predetermined far vision curvature and countersink size, produces a mould in which an organic lens may be cast.

Abstract: There is disclosed a method of producing a multifocal, ophthalmic lens blank wherein a glass major element is formed that has a raised countersink zone on one surface, the remainder of the glass major element being thinner than the countersink zone, but of such thickness that it can be ground and polished to form a lens, a countersink is formed in the countersink zone, a segment element is formed and is fused in the countersink to form a lens blank assembly.

Abstract: A method is disclosed for constructing a glass mould, and particularly the primary glass mould member, for use in casting multifocal, ophthalmic lenses from organic polymers. The method comprises pressing a glass segment with a cavity, removing the base portion of the segment to form a perforation, mounting the perforated segment on a second glass body, and fusing the assembly to form a blank for finishing. For trifocal lenses, a composite, perforated segment is formed and sealed in a depression on a major element to form a blank.

Abstract: There is disclosed a low expansion glass-ceramic substrate for supporting a glass multifocal lens assembly during a fusing or sagging heat treatment. The substrate has baked on its supporting surface a paint composed essentially of titania, alumina and a mica.

Abstract: There is disclosed an improved method of assembling and fusing the segment and major elements of a multifocal lens blank that employs glass spacer members to space the segment from the major element and allow the segment to progressively slump into sealing relationship with the major as fusion temperature is approached. The glass spacer member has a softening point that is lower than that of the major element glass and may approximate that of the segment glass.