Earlier contact lenses were made from glas, and were heavy and bulky. Only in the 1960s were they made from acrylic and thus small and light enough to stay in place. Polymethylmethacrylate, known either as acrylic or by the trade name 'Perspex', was introduced just before World War II. Its transparency made it immediately useful for aircraft glazing. Acrylic can be coloured and being a thermoplastic, can be easily moulded and shaped.
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