Two-Year Incidence of Myopia among Schoolchildren in China

Abstract

Purpose : Myopia is the most common type of refractive error affecting children. The WEPrOM (Wenzhou Medical University Essilor Progression and Onset of Myopia) study is a 4-year prospective cohort study that evaluates the incidence and progression of myopia, and associated risk factors in schoolchildren from urban and rural areas in Wenzhou, China. The present work aims to examine the incidence of myopia and associated risk factors over a 2-year period in this population.

Methods : The WEPrOM study is a prospective longitudinal study comprising 1,103 schoolchildren aged 7 to 11 years with complete refraction data at baseline visit. At 2-year follow-up (FU), 1,024 (92.8%) children were re-examined and had complete refraction data. Subjective refraction was measured at baseline and FU. Myopia was defined as a spherical equivalent (SE) of ≤ -0.5 diopters (D). Incident myopia was defined as the development of myopia (non-myopic at baseline and myopic at FU). Lifestyle questionnaires were filled at each visit by the parents.

Results : Among 1,103 schoolchildren at baseline visit, the prevalence rate of myopia was 19.2%. Of 891 non-myopes at baseline visit, 830 attended the 2-year FU. Over a 2-year period, the incidence rate of myopia was 27.6% (95% confidence interval [CI], 24.5-30.6%), with 229 of 830 schoolchildren who developed myopia. Less hyperopic SE (p<0.001), longer axial length (p=0.02), lower positive relative accommodation (PRA) (p<0.001) and female gender (p=0.005) were associated with incident myopia using multivariate logistic regression model. There was no significant difference in 2-year incidence of myopia between rural (27.2%; 95% CI, 21.2-33.2%; N = 217) and urban (27.7%; 95% CI, 24.2-31.3%; N = 613) schoolchildren. Age, parental myopia, outdoor time and nearwork time were not associated with incident myopia among schoolchildren.

Conclusions : The 2-year incidence rate of myopia among schoolchildren in Wenzhou was 27.6% (N = 830 at risk). This finding is in accordance with recent studies in China, where the cumulative incidence of myopia over a 2-year period was 36.2% among 1,385 schoolchildren aged 7 to 9 years in Shanghai. The incidence rates of myopia between schoolchildren residing in rural and urban areas were similar. Longer axial length, less hyperopic SE, lower PRA, and female gender appear to be predictors of myopia onset.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.