Ophthalmic lens retention in safety frames.

Lens retention in metal and zyl safety frames was tested using both a high mass (500 g), low velocity impact (HM-LV), and a low mass (1.04 g), high velocity impact (LM-HV) for plano polycarbonate lenses of various thicknesses. The results showed that the metal safety frames retained lenses better than the zyl (p < 0.01) after a HM-LV impact. For the LM-HV impact, metal and zyl frames performed equally (p = 1.00). Lens thickness was not a factor in lens in frame retention for the HM-LV impact (p = 0.958). However, for the LM-HV impact, 1.6-mm thick lenses were more easily displaced than lenses with thicknesses of 2.0, 2.4, and 3.2 mm (p = 0.003).