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 (366KB)
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17,305,000 Yen (FY1998; 6,252 Yen)
Cataract figures may differ among races and environmental conditions, including climate, but only a few studies with a reliable approach have been made to confirm these differences. Since the early 1990s, the influence of solar UV rays on human eye diseases, cataract in particular, has become a global concern. In order to clarify this scenario of UV-induced cataract formation in human eyes, further experimental and epidemiological studies have been required. Based on the above concept, epidemiological cataract studies have been carried out in two places in Japan (Noto and Amami) and three places overseas (the cities of Reykjavik, Iceland, Singapore, and Melbourne, Australia, for apreliminary survey). The methodology applied in each survey was the same as that of the Noto study. The examiners were the same throughout each survey. Among the items examined, a decrease of physiological lens transparency with ageing, prevalence of cataract including whole types, pterygium and the preventative effect of wearing sunglasses against pterygium formation are discussed in this report. Although the decrease of lens trans parency with ageing was different in each group, there were similarities between the lcelanders and Japanese, and Noto, Amami and Singapore, respectively. There were however, clear differences between the former two and latter two groups in the subject, in their 60s and 70s. The clinical definition of cataract generally includes cortical, nuclear and subcapsularlens opacification, even though their formation mechanisms are not the same. The comparison of cataract prevalence (including whole types) with rather progressed stages among the Noto, Singapore and Reykjavik groups showed a significant relationship with the irradiation dose of solar UV-B . Cataract progression seemed to appear in the Noto subjects about 10 years earlier than in the Reykjavik subjects and 10 to 15 years later than in the Singapore subjects. Among the three types of lens opacification, cortical was most frequently seen. The prevalence of cortical cataract was significantly lower in the Reykjavik subjects than in Noto, Amami and Singapore, In addition, the prevalence of nuclear cataract was significantly higher in Amami and Singapore than in Noto and Reykjavik. From this study, the authors would like to consider that the scenario of UV-induced cataract is acceptable at least for the cortical type of cataract. The prevalence of pterygium in Noto, Amanri, Singapore and Reykjavik was 6.4%, 25.4%, 11.2% and 0.2%, respectively. The preventative effect of wearing sunglasses against pterygium formation was noticed in the subjects of Singapore by a case and control study.
cataract, UV-B, risk factors, Iceland, Singapore, Noto Japan, epidemiological survey