Abstract
Abstract: :
Purpose: To perform a population based epidemiological study on pterygium in Japan, Singapore and Iceland and to investigate the correlation between cumulative ocular UV exposure (COUVest) and pterygium. Methods: 977 subjects from Noto, Japan, 337 from Amami Japan, 514 from Singapore and 1,045 from Reykjavik, Iceland were examined. Pterygium was detected by slit-lamp microscopy as conjunctival tissue covering the surface of the cornea. COUVest was estimated by the amount of time an individual spent outdoors during their lifetime (TSO), obtained from the questionnaire, the ambient UV intensity of their living place, and the wearing of glasses and hats. Total TSO was calculated from TSO on weekdays × years. Since TSO before the age of 20 was difficult to determine, two hours a day was used in all the groups. In this study, the protective rate against UV of wearing glasses and hats was 90% and 20%, respectively, which was estimated by a mannequin model experiment. The ambient UV intensity in Amami, Singapore and Iceland was 1.4, 2.1 and 0.4 times that of Noto. Results: : The prevalence of pterygium in the subjects of Noto, Amami, Singapore and Iceland was 7.1%, 25.5%, 11.2% and 0.2%, respectively. They showed weak age dependency. The mean COUVest was highest in Amami, followed by Singapore and Noto subjects, while that in Iceland was extremely low. In the Singapore, Noto and the Amami, COUVest was higher in the subjects with pterygium and the difference was significant in the Singapore and Noto. In the Singapore, COUVest was 1.3 to 2.0 times higher in the subjects with pterygium for each age group. Conclusion: The prevalence of pterygium was significantly higher in the Amami subjects whose COUVest was the highest. There was a significant correlation between the COUVest and the risk of pterygium. The results suggest that it is important to measure COUVest when considering the effect of UV on ocular diseases.
Keywords: 532 Pterygium • 355 clinical (human) or epidemiologic studies: risk factor assessment • 354 clinical (human) or epidemiologic studies: prevalence/incidence