plastic spectacle frame
spectacle frame, plastic
A structure in plastic for enclosing or supporting ophthalmic lenses. Common materials include carbon fibre composite materials, which are a mixture of principally carbon and nylon in different percentages, cellulose acetate, cellulose propionate, nylon, epoxy resin (trade name Optyl), and Perspex and Plexiglas (which are both trade names for acrylic plastics containing mainly polymethyl methacrylate). Most of the plastics used are thermoplastic, i.e. a material which softens with heat and can thus be manipulated to fit the patient's head and to insert and remove the lenses. See frame heater; polymethyl methacrylate.