Physical characteristics of various intraocular lenses

Physical characteristics of 15 posterior chamber lenses from 15 companies were examined for residual ethylene oxide gas; the content varied from 13 ppm to 78 ppm. Seven lenses met the FDA regulation of less than 25 ppm. Scanning electron microscopic study revealed that molded-type lenses had the smoothest optic surface and cast-molded lenses had a less smooth surface than the plano side. The lathe-cut lens with barrel polishing also had a smooth optic surface. Neodymium: YAG laser shots were delivered to the optic and the spots were examined by phase contrast microscopy. The lenses made of high molecular weight polymethylmethacrylate were more resistant to YAG laser damage. It was concluded that lathe-cut posterior chamber lenses with barrel polishing made of high molecular weight polymethylmethacrylate would be preferable but further studies of polishing compounds are necessary.