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J.D. Twelker, I.L. Bailey; Sun Exposure in Unilateral and Bilateral Pterygium Cases . Invest. Ophthalmol. Vis. Sci. 2003;44(13):816.
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Purpose: A pterygium is a triangular corneal lesion, usually located on its nasal and interpalpebral surface. As part of a larger case-control study of risk factors for pterygium, we investigated the sun exposure history and ocular characteristics of cases with pterygium. Methods: We examined 90 study subjects with primary pterygium. The examination included a general health and ocular history, anterior segment examination, latitude of residence, history of sunlight exposure beginning at age 16 years, and some biometric measures. Results: The average age of the subjects with pterygium recruited for this study was 42.7 years (SD=12.7). The average reported age of onset of the pterygium was 31.8 years (SD=11.4). The average length of encroachment onto the cornea was 1.47mm (SD=0.81). Thirty-eight (42%) of cases were unilateral, with 20 (22%) in the right eye and 18 (20%) in the left eye. Fifty-two (58%) were bilateral. All cases had pterygium located on the nasal aspect of the cornea, and in 4 cases there were lesions on the temporal side as well. Cases were stratified into two groups, unilateral and bilateral lesions. Subjects with unilateral cases of pterygium were born in higher latitudes than subjects with bilateral cases (25.8 degrees vs. 21.5, respectively; p=0.02, two-sided unpaired t-test). Subjects with unilateral cases of pterygium received lower sun exposure from the ages of 16 to 19, than bilateral cases (0.09 versus 0.11 Maryland Sun Years (MSY) per year, respectively; p=0.0001, two-sided unpaired t-test). Subjects with unilateral cases of pterygium received lower sun exposure from the ages of 20-29, than bilateral cases (0.07 versus 0.08 MSY per year, respectively; p=0.037, two-sided unpaired t-test). There was no difference in sun exposure between unilateral and bilateral cases for exposures from ages 30-39, 40-49, 50-59, 60-69, or cumulative lifetime exposure. Conclusions: As compared to subjects with unilateral pterygium, subjects with bilateral pterygium were more likely to have received greater sun exposure during their youth (16 to 29 years). To achieve maximum effect, pterygium prevention and education efforts should be targeted toward young persons in occupations or recreations in sunny environments.
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