Prevalence of amblyopia and strabismus in Eastern China: results from screening of preschool children aged 36–72 months

Abstract

PURPOSE: To determine the prevalence of amblyopia and strabismus in preschool children in Eastern China. METHODS: The Nanjing Pediatric Vision Project was a cross-sectional, population-based cohort study conducted in preschool children aged 36-72 months from 2011 to 2012 in Yuhua District, Nanjing, China, using an age-stratified random sampling procedure. A questionnaire totalling 117 items was sent to be completed by the corresponding parents or legal guardians of each eligible child. Comprehensive eye examinations, including visual acuity, anterior segment examination, autorefraction, cover test and ocular motility, were conducted. Postcycloplegic refraction and fundus examinations were performed if necessary. RESULTS: Amblyopia was present in 68 children (1.20%, 95% CI 0.92% to 1.48%), with no statistical differences in gender (p=0.903) and age (p=0.835). Among these, 27 had bilateral amblyopia and 41 had unilateral amblyopia, including 26 anisometropic without strabismus, 26 binocular refractive, 7 strabismic, 6 combined strabismic/anisometropic and 3 deprivation amblyopia. Strabismus was found in 320 children (5.65%, 95% CI 5.05% to 6.25%), including 43 with concomitant esotropia, 259 with concomitant exotropia (1 esotropia at near but exotropia at distance), 8 with microtropia (3 esotropia and 5 exotropia), 10 with pure vertical strabismus (3 dissociated vertical deviation and 7 oblique muscle dysfunction) and 1 with Type I Duane syndrome. The prevalence of strabismus had no statistical differences in gender (p=0.952), but had significant statistical differences between different age groups (p=0.021). CONCLUSIONS: The prevalence of amblyopia and strabismus in preschool children in Eastern China were 1.20% and 5.65%, respectively. The refractive and strabismus are the main factors associated with amblyopia.