Study design, rationale and methods for a population-based study of myopia in schoolchildren: The Myopia Investigation study in Taipei

Background: To describe the study design, rationale and methodology of the Myopia Investigation Study in Taipei (MIT). Design: The MIT was a citywide, population-based cohort study. Participants: Participants were grade 2 students (Fall 2013) of all 153 elementary schools in Taipei City. Methods: The baseline data on the risk factors for myopia development was collected by parent-administered questionnaire surveys covering demographics, medical history, parental myopia, time spent on near work and outdoor activities, reading habits and eye care-seeking behaviour. Ocular examinations focused on the measurement of visual acuity (unaided and best-corrected) and refractive status (before and after cycloplegia), which will be carried out for the eligible schoolchildren biannually for 3 years consecutively. Once myopic children are identified, case manager-led telecoaching for health-care instructions and reminders will be delivered to parents or caregivers. Main Outcome Measures: To build a comprehensive database for prevalence, incidence and risk factors of early childhood myopia over a 3-year follow-up period. Results: Of all 19374 eight-year-old schoolchildren (10210 [52.7%] boys) eligible for the MIT, 16486 (85.1%) responded to the questionnaire, 12019 (62.0%) were examined during the third quarter of 2013 and 11590 (59.8%) (6267 [52.9%] boys) completed cycloplegic autorefraction on both eyes and were enrolled for further data analysis. There was no significant difference in terms of demographics between the analysed participants and all grade 2 students in Taipei City. Conclusions: Data from the MIT will provide population-based information concerning the prevalence, incidence and risk factors for myopia development among young schoolchildren in a metropolitan area of Taiwan.