Design, Methodology and Baseline Data of a School-based Cohort Study in Central China: The Anyang Childhood Eye Study

Purpose: To report the design, methods and baseline data of the Anyang Childhood Eye Study (ACES), aiming to determine the prevalence, incidence and risk factors of myopia and other ocular diseases in children in central China. Methods: The ACES was a school-based cohort study conducted in Anyang city. Students have been examined and will be followed-up annually for 3-5 years. Ocular examinations included visual acuity, identification of amblyopia and strabismus, ocular biometry, optical coherence tomography, retinal photography, cycloplegic autorefraction, accommodative response, peripheral refraction, visual perception and so on. A questionnaire survey was performed to collect risk factors for myopia including near work, outdoor activity, parental myopia, birth history, habits of wearing spectacles and reading, living habits, food habits and so on. Results: Of 3112 grade 1 and 2363 grade 7 students eligible for the ACES, 2893 (93.0%) and 2267 (95.9%) participated in the study, with a mean age of 7.1 years (range 5.7-9.3 years) and 12.7 years (range 10.0-15.9 years), and proportions of male to be 57.8% and 50.0%, respectively. The prevalence rates of myopia, high myopia, emmetropia and hyperopia were 3.9%, 0.1%, 72.9% and 23.3% in grade 1, and 67.3%, 2.7%, 31.4% and 1.2% in grade 7, respectively. Similar data were found in the children confined in 6-year-old and 12-year-old ages. Conclusions: The ACES is the first large-scale cohort study in China with baseline response rates over 90%. Continuous documentation of changes and risk factors of refractive errors in these cohorts would provide new insights into myopia control in school-aged children.