Abstract: A mixture of a specified siloxanylalkyl ester monomer and a specified vinyl monomer is polymerized by exposure to an ionizing radiation at low temperatures and the resulting polymer is worked with a lathe cut to form a contact lens. The contact lens obtained is free from any optical distortion, has good dimensional stability and exhibits high oxygen permeability. In a preferred embodiment, a monomer mixture comprising a siloxanylalkyl ester, a methacrylate or acrylate, N-vinylpyrrolidone, and a small amount of a dimethacrylate or diacrylate is exposed to a total dose of 1.times.10.sup.5 -5.times.10.sup.6 roentgens at a low temperature (-80.degree. C. to -20.degree. C. and at a dose rate of 8.times.10.sup.4 -2.times.10.sup.6 roentgens per hour, and the resulting polymer is worked into a contact lens by a suitable forming process involving cutting, grinding and polishing operations.