Abstract: A method for forming a thermoplastic preform into a lens by compression molding between a pair of molds is provided. In another aspect of the invention a set of novel preforms made from a thermoplastic material is provided. The preforms have different radii of curvature. Preferably each different curvature preform comes in different weights desirably two or three different weights. A series of mating concave and convex mold halves are provided for use with the preforms. According to the invention a limited number of concave mold halves are provided. A wide range of single vision and multifocal lenses can be supplied from three (3) to six (6) base curve concave molds halves having different radii of curvatures. According to the invention a first concave mold half with a radius of curvature of less than two (2) diopters is provided. Each successive concave mold half has a radius of curvature of from one (1) to three (3) diopters greater than the previous mold half in the series.