Prevalence, incidence, and progression of myopia of school children in Hong Kong.

PURPOSE To determine the prevalence, incidence, and progression of myopia of Chinese children in Hong Kong. METHODS A cross-sectional survey was initially conducted. A longitudinal follow-up study was then conducted 12 months later. RESULTS A total of 7560 children of mean age 9.33 (95% confidence interval [CI] = 9.11-9.45; range, 5-16) participated in the study. Mean spherical equivalent refraction (SER) was -0.33 D (SD = 11.56; range, -13.13 to +14.25 D). Myopia (SER <or= -0.50 D) was the most common refractive error and was found in 36.71% +/- 2.87% (SD) of children. Prevalence of myopia correlated positively with older age. Children aged 11 years were almost 15 times more likely to have myopia than were children younger than 7 years (Odds ratio [OR] = 14.81; 95% CI = 14.17-15.48). Incidence of myopia was 144.1 +/- 2.31 (SD) per 1000 primary school children per annum. Increasing age was correlated with increased incidence of myopia, with highest risk in children ages 11 years (OR = 2.27; 95% CI = 2.11-2.44). The average annual change in SER for children with myopia (SER <or= -0.50 D) was -0.63 D (SD = 3.44) compared with -0.29 D (SD = 2.96) for those who were not myopic at the beginning of the study (P < 0.001). CONCLUSIONS The results show that the prevalence and progression of myopia in Hong Kong children was much higher than those previously reported in Western countries. The long-term socioeconomic impact of these findings warrants further studies.