Abstract: A polymeric bifocal lens production process including the steps of selecting a single vision lens or lens blank with a convex surface, and a bifocal mould with a smaller radius of curvature; toughening the convex surface of the lens or lens blank; assembling the mould and lens or lens blank with catalysed monomer between the mould and the lens or lens blank; holding the lens or lens blank and the mould in position relative to one another so that the lens or lens blank contacts the mould; curing the monomer; removing the mould and post-curing to relieve stress in the bifocal lens and to allow the cured monomer to shrink in a controlled manner thereby causing a power decrease in the bifocal segment, whereby the cured monomer cast on to the lens or lens blank is of higher refractive index than the lens or lens blank.