Myopia development among young schoolchildren: The myopia investigation study in Taipei

PURPOSE. To investigate the annual incidence of myopia and associated factors among young schoolchildren in Taipei City. METHODS. The Myopia Investigation Study in Taipei was a citywide, population-based cohort study. During the fall 2013 semester (baseline), a total of 11,590 grade 2 schoolchildren completed ocular examination and were included for further analysis. A parent-completed questionnaire was administered to collect data on risk factors for myopia development. Follow-up visits were arranged biannually over 3 years. The first-year results are reported here. Schoolchildren who were emmetropic/hyperopic at baseline and had myopia (spherical equivalent ≤ -0.5 diopters) in either eye at follow-up were identified as having incident myopia. RESULTS. Among 7376 baseline nonmyopic participants, 6794 (92.1%) were examined during the first-year follow-up, and 1856 (25.2%) with incident myopia were identified. The incidence density of myopia was 31.7 (95% confidence interval [CI]: 30.6-32.8) per 100 person-years. Cox hazard proportional regression analysis revealed that participants who were emmetropic at baseline (hazards ratio [HR]: 19.37; 95% CI: 4.84-77.57), who had two myopic parents (HR: 1.21; 95% CI: 1.04-1.42), and who spent ≥5 hours every week on afterschool tutoring programs (HR: 1.12; 95% CI: 1.02-1.22) had greater risk for incident myopia. By contrast, protective factors included suburban area of residence (HR: 0.91; 95% CI: 0.83- 1.00) and spending ≥30 minutes outdoors after school every weekday (HR: 0.90; 95% CI: 0.82-0.99). CONCLUSIONS. This study provides population-based data on the annual incidence of myopia among Taiwanese schoolchildren, and found that baseline refractive status, parental myopia, area of residence, time outdoors after school on weekdays, and time spent on after-school tutoring programs are associated with risk of new-onset myopia.