Impact Resistance: An Optical Perspective

Abstract

The purpose of this review paper is to provide information about an aspect that is rarely taken into account (mainly due to the lack of documented material, either written or published) at the time of issuing a prescription for someone requiring optical aid. The contribution of an ophthalmic lens to the safety and health of the patient, regardless of the material it is manufactured with, was analyzed from different points of view. The impact resistance of an optical system depends on many aspects, including: lens thickness, the refractive index of the material, the base curve used for its manufacture and the application or not of optical treatments, such as anti-scratch, anti-glare and photosensitive. All analyzes of this issue are performed on studies based on indications given by institutions such as the ANSI (United States), OLA (United States), CSA (Canada) and AS/NZS (Australia), to apply tests that measure lens resistance, such as the Drop Ball Test, as well as speed and high impact ballistic tests. It can be concluded that polycarbonate is the most durable material and that center thickness is directly related to the strength of the lens. Furthermore, the flatter the base curvature is, the greater the fragility of the material, and the antiglare treatment directly affects the decrease in impact resistance, unlike photosensitive treatments, which do not alter this property.