Epidemiologic study of ocular refraction among schoolchildren in Taiwan in1995

Purpose. In order to understand and update the prevalence of myopia in Taiw an, a nationwide survey was performed in 1995. Methods. We stratified the c luster sampling by developmental grading of the city, using a size proporti onal to the population, Two cities were randomly selected from each city gr ading. The total number of students enrolled was 11,178, including 5,676 bo ys and 5,502 girls. The refractive status and corneal radius of each studen t were measured with an autorefractometer under cycloplegia and checked wit h retinoscopy, Axial length was measured with biometric ultrasound. Results . The myopic rate was from 12% at the age of 6, it increased to 56% at the age of 12, and then to 76% at the age of 15. A myopic rate of 84% was found for the age range of 16 to 18. The prevalence of high myopia (over -6.0 D) at the age of 18 was 20% in girls and 12% in boys. The mean refractive sta tus became myopic at the age of 9, then increased to -3.92 D in girls and - 2.71 D in boys at the age of 18. The increase of axial length is correspond ent with the progression of myopia. The anterior chamber depth (ACD) was de eper with age and the severity of myopia, whereas the corneal curvature rem ained unchanged. The lens thickness became thinner from age 7 to 13, then i t became thicker with age and the severity of myopia after age 15. The prev alence and degree of myopia in girls was more severe than in boys. Conclusi ons. The prevalence of myopia in Taiwan increased year by year. The increas e in severity and prevalence of high myopia may be due to earlier onset.