Studies of Genetic and Environmental Factors in the Occurrence of Myopia Based on Epidemiologic Data
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The present study investigated the role of genetic and environmental factors in the occurrence of myopia based on epidemiologic studies performed in Shanghai, China. The prevalence of myopia in high school students in one district of Shanghai in 1965 was 56%. During the “Cultural Revolution” (1966–1976), students lost their diligent study habits, and the need for the use of near vision was decreased. By 1977, the prevalence of myopia was reduced to 27%. After the Cultural Revolution ceased, the prevalence of myopia increased to 62% by 1983 and to 70% by 1985. In a retrospective study, the prevalence of myopia in 515 students (average age, 14 years) was 55% with 4–5 h near work per day, 39% with 3 h per day, and 28% with 1–2 h per day. The prevalence of myopia was 59% when both parents were myopic, 41% when one parent was myopic, and 31% when both parents were not myopic. In the prospective study, after 2 years of follow-up, the incidence of myopia in the previously nonmyopic eyes was 26% in the 4- to 5-h group, 17% in the 3-h group, and 8% in the 1- to 2-h group. In a study of 82 pairs of twins with simple myopia, the concordance rate of myopia was 82% in monozygotic twins and 58% in dizygotic twins. The heritability index of myopia was 61%. Our studies indicate that both genetic and environmental factors play an important role in the occurrence of myopia.
Key WordsMyopia Genetics Environment Epidemiology Twin study
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