To compare the prevalence and risk factors for myopia in 6-and 7-year-old children of Chinese ethnicity in Sydney and Singapore. Methods: Two cross-sectional samples of age-and ethnicity-matched primary school children participated: 124 from the Sydney Myopia Study and 628 from the Singapore Cohort Study on the Risk Factors for Myopia. Cycloplegic autorefraction was used to determine myopia prevalence (spherical equivalent Յ −0.5 diopter). Lifestyle activities were ascertained by questionnaire. Results: The prevalence of myopia in 6-and 7-year-old children of Chinese ethnicity was significantly lower in Sydney (3.3%) than in Singapore (29.1%) (PϽ.001). The prevalence of myopia in 1 or more parents was 68% in Sydney and 71% in Singapore. Children in Sydney read more books per week (PϽ.001) and did more total nearwork activity (P =.002). Children in Sydney spent more time on outdoor activities (13.75 vs 3.05 hours per week; P Ͻ.001), which was the most significant factor associated with the differences in the prevalence of myopia between the 2 sites. Conclusions: The lower prevalence of myopia in Sydney was associated with increased hours of outdoor activities. We hypothesize that another factor contributing to the differences in the prevalence of myopia may be the early educational pressures found in Singapore but not in Sydney.

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Retinal vessel diameter may predict risk of CHD and stroke deaths in middle-aged persons.