The transmittance and absorption properties of contact lenses

The transmittance and absorption properties of certain soft-lens materials with a low and a high water content and a hard-lens material were analyzed by a spectrophotometric technique over a broad spectrum from ultraviolet (195 nm) to far infrared (40,000 nm) radiation. The dry lens materials not only showed marked absorption within the short-wave region of ultraviolet, but also very strong absorption within the infrared range, especially medium and far infrared. Wet soft-lens material showed greatly increased absorption within the infrared regions in which water shows absorption maximums. Therefore the wet soft-lens materials absorbed nearly 100% of the radiation within the greater part of the medium and far infrared ranges. Transmittance and absorption were inevitably affected by the thickness of the material, but differences between the various makes of lens were minor. It is clear that sources of high-energy radiation, particularly within the infrared spectra, may constitute hazards with regard to the absorption of radiation and the consequent generation of heat in contact lenses.