Abstract. Perspex, a polymer of methyl methacrylate, possesses all the attributes, except hardness, desirable in a material for spectacle lenses. It is especially resistant to impact and splintering and is extraordinarily light in weight. Experiments are described illustrating (a) that surface scratches, arising because of the relative softness of Perspex, are not so troublesome to vision as might be supposed; (b) the resilience and resistance to splintering of Perspex. The manufacture of plastic lenses, in which the lapping operations necessary with glass are replaced by a simple moulding operation, is briefly described. Plastic lenses for binoculars, telescopes and photography, as well as plastic spectacle lenses, are in production.

Print publication: Issue 4 (1 July 1943)