Sun exposure and pterygium of the eye: A dose-response curve

PURPOSE: To present a quantitative analysis of pterygium and ocular sun exp osure, a dose-response curve, and a discussion of the health-promotion impl ications of the findings, METHODS: A hospital-based, case-control study was conducted in Perth, Weste rn Australia. Case subjects had surgical removal of a pterygrum; control su bjects had an ear, nose, or throat procedure. A lifetime history of residen ce, sun exposure patterns, and use of hats, spectacles, and sunglasses was obtained at interview. Measures of potential sun exposure included latitude , daily sunshine hours, and daily global solar radiant energy. The most com plex estimate of actual sun exposure was the daily ocular solar radiation d ose, calculated from climatic data, time spent outdoors not under shade, an d the use of hats and spectacles. RESULTS: There were strong positive associations between pterygium and meas ures of potential and actual sun exposure. Associations were as strong for whole-life measures as for those in any specific age range. Pterygium odds ratios increased with exposure level; the odds ratio was 4.0 (95% confidenc e interval, 1.6 to 10.9) for the highest quarter of the daily sun exposure. . The strongest associations were seen for the estimated daily ocular solar radiation dose, with an odds ratio of 6.8 (95% confidence interval, 2.6 to 19.1) for the highest quarter of exposure. CONCLUSIONS: Pterygium is strongly related to ocular sun exposure, with lit tle evidence that exposure during any particular period of life is more imp ortant than in other periods; the implication for prevention of pterygium i s that ocular protection is beneficial at all ages. (Am J Ophthalmol 1999; 128:280-287 (C) 1999 by Elsevier Science Inc. All rights reserved.)