Estimating the solar ultraviolet radiation exposure to an intraocular lens implant

A study of the stability of ultraviolet radiation (UVR) absorbers in intraocular lenses (IOLs) upon exposure to UVR is necessary to determine efficacy. Ultraviolet stability is conventionally tested by placing the UV-absorbing IOLs in a solar simulator exposure chamber to determine any degradation of the absorber. To interpret any change requires a method of correlating the UVR exposure rate in the test chamber with the UVR exposure of the IOL in vivo. A method is derived that permits a determination of the upper limit of daily UVR exposure of the in-vivo IOL (or, for that matter, the crystalline lens) based upon knowledge of the ambient outdoor UVR exposure to the head and the threshold for photokeratitis.