Abstract: Although special attention to children’s myopia by society and government, and taking many measures for its control, the prevalence of children’s myopia is not decrease but continuously increases. This paper will explain the causes of high prevalence of children’s myopia with plot of epidemiological surveys in deferent regions. Firstly, the prevalence of children’s myopia is correlated with age. Secondly, civilization, modernization and smaller activity space are risk factors of myopia. Thirdly, for recent 10 years the prevalence of myopia has significantly been increasing. Fourthly, the prevalence of primary students is correlated with strong preschool education. We quote some researches and illustrate that myopia is caused by long-term near-distance activity and lacking of outdoor activity. (Ophthalmol CHN, 2012, 21: 1-2)

Key words: myopia control, epidemiology, outdoor activity