Epidemiologic study of the prevalence and severity of myopia among school children in Taiwan in 2000

Background and Purpose: A nationwide survey was performed in 2000 to determ ine the prevalence and severity of myopia among schoolchildren in Taiwan an d to compare these findings with the results of the last survey, performed in 1995. Methods: We first divided the whole island into regions according to develo pmental grade scores and their sampled with the probability proportional to the size of tile population,, within each stratum. A total of 10,889 stude nts were enrolled, including 5,664 boys and 5,225 girls, with ages ranging from 7 to 18 years. 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 using biometric ultrasound. Results: The myopia rate increased from 20% at 7 years, to 61% at 12 years, and 81% at 15 years. A myopic rate of 84% was found for schoolchildren age d 16 bears through 18 years. The mean refractive index reached myopic statu s at the age of 8, and increased to -4.12 D in girls and -3.15 D in boys at the age of 18-years. The prevalence of high myopia (> -6.0D) at the age of IS years was 24% in girls and 18% in boys. The increase in axial length co rresponded with the progression of myopia. The anterior chamber depth was s lightly deeper from 7 years to 13 years and their remained stable. The lens thickness decreased from 7 years to I I years. After age 15, further thick ening of the lens was correlated with both age and severity of myopia. Howe ver, the cortical curvature was not related to age or severity of myopia. G irls had a higher prevalence and more severe degree of myopia than boys. Ch ildren in urban areas had a higher prevalence and more severe degree of myo pia than children in rural areas. Conclusion: The prevalence and severity of myopia in schoolchildren in Taiw an in 2000 increased compared to 1995, with the most severe increases occur ring in younger age groups. Thus, preventing schoolchildren developing myop ia at a young age may slow clown the increase in severity Of myopia in Taiw an.