title: Material and thickness: the important factors in the impact resistance of spectacle lenses.
abstract: The identify the population at risk of permanent visual impairment from injuries associated with spectacles, we analysed 446 cases of penetrating ocular injury occurring over a ten year period. Sixteen injuries (3.6%) were due to spectacles; 40% of these were adult male amateur athletes. We used the drop-ball test to determine the important factors in the resistance to impact of 177 used spectacle lenses (29 plastic C39, 40 heat-tempered glass, 108 non-tempered glass). We found that material and thickness were the most important. The plastic lenses were the most impact resistant and non-tempered glass lenses the least, with heat-tempered glass lenses falling between. Plastic lenses of adequate centre thickness mounted in plastic frames are recommended for all children and all adults involved in athletics.
mesh_terms: D000293:Adolescent; D000328:Adult; D001265:Athletic Injuries / Q000209:etiology*; D002648:Child; D005131:Eye Injuries / Q000209:etiology*; D005139:Eyeglasses / Q000592:standards*; D005260:Female; D005898:Glass / Q000592:standards; D006801:Humans; D008297:Male; D010969:Plastics / Q000592:standards; D012306:Risk; D013177:Sports
chemical_list: D010969:Plastics