Abstract: Polymeric replica molds formed from certain specific polymeric compositions are disclosed. The polymeric compositions impart properties to the replica molds which allow the casting of high-quality plastic optical components such as ophthalmic lenses.Among the polymeric compositions which have been found useful are: (1) cross-linked polymethyl methacrylate; (2) a copolymer of 99-20 parts methyl methacrylate and 1-80 parts acrylonitrile, preferably but not necessarily cross-linked; (3) cross-linked polystyrene; (4) a cross-linked copolymer of 90-10 parts styrene and 10-90 parts acrylonitrile; and, (5) a cross-linked copolymer of 90-10 parts styrene and 10-90 parts methyl methacrylate.Replication processes including the steps of forming the polymeric replica molds described herein and subsequently using them in the casting of plastic lenses from materials such as polymerized allyl diglycol carbonate are also disclosed.