ULTRAVIOLET RADIATION OCULAR EXPOSURE DOS/MErRY OF THE EYE

Acareful studyof ocularexposure to environmental sunlight demonstrates that it is not at all simple to accurately determine the level of solar ultraviolet radiation exposure of the human eye. Epidemiological studiesof cataract depend heavily upon realistic and reasonably accurate dosimetry of UVR exposure. Unfortunately, most pastattempts to measure or calculate UVR exposure of theeyeforsuch studieshave generally relied upon monitors to measure the ambient UVR insunlighL falling upona horizontal surface (i.e.,theglobal UVR), Thisapproach is insufficient to properly assess the large role of ground reflection, the horizon skycontribution! the degree of lidopeningand the extreme lateral component of UVR incident on the eye. Currentdosimetric estimates may leadto incorrect assignment of lifetime exposures to different cohorts. This report summarizes a series of recent oculardosirnetry studies undertaken La assess all of these factors. Analgorithm is developed for calculating ocularexposure for a given environment AddilioI'1ally, the value of different types of eye protection isshownto vary widely depending upon frame design. Thedosimetry studiescanbeconfirmed bya biological dosimeter the human cornea. Because the action spectrum and threshold for the human corneaare well defined, the living cornea actually serves as a biological dosimeter to callbrate this method for calculating ocular exposure. More accurate dosimetric methods are expected to aid in the resolution of the current controversy as to theeuologic role ofUVR in cataract andotheroculardiseases. Concerns about the depletion ofstratosphenc ozoneand the related increase in terrestrial UVR exposure have emphasized the importance of resolving thiscontroversy.