Dynamic strain gage measurements on ophthalmic lenses impacted by low energy missiles

Strain distributions on impacted ophthalmic lenses were measured with strain gages. The strain distributions, which resulted from impacts produced with a special apparatus, were shown to be comparable to those which arise in the FDA drop-ball test. The measured strain drops off very rapidly away from the impact point, implying that only a small part of the lens is really being tested. The results are in good agreement with the quasi-static predictions. The effect of differences in lens power, of input kinetic energy, and of inserting the lens in a polyethylene bag are also investigated.