The Reykjavik Eye Study - Prevalence of lens opacification with reference to identical Japanese studies

Purpose: A population-based cataract epidemiological study, the Reykjavik E ye Study, was conducted to determine the prevalence and characteristics of lens opacities in Iceland. The results were compared with those from previo us surveys in Japan to determine the influence of race and environmental fa ctors. Methods: 1,635 randomly selected residents of Reykjavik, Iceland, we re enrolled, and among them, 1,045 responded and took part in the study. Th e subjects received ophthalmological examination of both the anterior and t he posterior segments. Changes in the crystalline lens were examined and ph otographed under maximal pupillary dilation. Classification of the opacity types and grading of the extent of lens opacificiation were done using a st andardized scheme, and the data were analyzed with Student's test, the chi (2) test and the Mantel-Haenszel test. Results: The prevalence of lens opac ities in subjects in their 50s, 60s, 70s and in those 80 years and older wa s 42.7, 61.0, 85.3 and 100%, respectively. Grade II and III lens opacities were found in 2.2% of subjects in their 50s and in 10.5, 35.9 and 62.3% in their 60s, 70s, and over 80 years, respectively. Cortical opacities predomi nated in all age groups followed by nuclear opacities; subcapsular opacitie s, on the other hand, were quite rare. A unique type of opacity, i.e., gran ular opacity, seldom seen among the Japanese, was found in 6.6% of the Icel andic subjects. Conclusions: Our results show that cortical opacity is the major type of opacity in Icelandic subjects, although its prevalence was lo wer than that in the Japanese subjects. Interestingly, the first appearance of lens opacities of grades II and III in Icelanders was delayed by 10 yea rs compared to the Japanese suggesting fewer or less severe risk factors fo r cataract formation in Iceland. Copyright (C) 2000 S. Karger AG, Basel.