Polycarbonate Versus CR-39 Lenses: A Field Study

During the Indochina hostilities, prescription-wearing U.S. military members were issued conventional spectacle lenses which were worn in the combat zone. These lenses, if shattered by impact, could produce secondary missiles which could be eye threatening. Polycarbonate Lexan lenses could provide significant impact protection in hazardous environments. This study explored the response by industry to a request to produce a range of prescription lenses in dress thickness and the scratch-resistance capability of a state-of-the-art protective coating applied to the polycarbonate-lense surfaces. In their usual pursuits over a years period in desert-type environment, 100 subjects wore prescription spectacles containing CR-39 and companion polycarbonate lenses. The polycarbonate lenses with coating protection were more scratch-vulnerable than conventional plastic spectacle lenses CR-39. The eye-protection property of the polycarbonate lens warrants the issue of plano or prescription spectacles containing this material to military members who are likely to be in a combat area.