Participants who spent more time outdoors were less likely to be myopic. Thus, outdoor activity may protect against development of myopia in children, supporting recent Australian data. As near work did not predict outdoor activity, this can be viewed as an independent factor and not merely the reciprocal of near work.

PURPOSE. To determine the prevalence of amblyopia and strabismus in young Singaporean Chinese children. METHODS. Enrolled in the study were 3009 Singaporean children, aged 6 to 72 months. All underwent complete eye examinations and cycloplegic refraction. Visual acuity (VA) was measured with a logMAR chart when possible and the Sheridan-Gardner test when not. Strabismus was defined as any manifest tropia. Unilateral amblyopia was defined as a 2-line difference between eyes with VA < 20/30 in the worse eye and with coexisting anisometropia (> or =1.00 D for hyperopia, > or =3.00 D for myopia, and > or =1.50 D for astigmatism), strabismus, or past or present visual axis obstruction. Bilateral amblyopia was defined as VA in both eyes <20/40 (in children 48-72 months) and <20/50 (<48 months), with coexisting hyperopia > or =4.00 D, myopia < or = -6.00 D, and astigmatism > or =2.50 D, or past or present visual axis obstruction. RESULTS. The amblyopia prevalence in children aged 30 to 72 months was 1.19% (95% confidence interval [CI], 0.73-1.83) with no age (P = 0.37) or sex (P = 0.22) differences. Unilateral amblyopia (0.83%) was twice as frequent as bilateral amblyopia (0.36%). The most frequent causes of amblyopia were refractive error (85%) and strabismus (15%); anisometropic astigmatism >1.50 D (42%) and isometropic astigmatism >2.50 D (29%) were frequent refractive errors. The prevalence of strabismus in children aged 6 to 72 months was 0.80% (95% CI, 0.51-1.19), with no sex (P = 0.52) or age (P = 0.08) effects. The exotropia-esotropia ratio was 7:1, with most exotropia being intermittent (63%). Of children with amblyopia, 15.0% had strabismus, whereas 12.5% of children with strabismus had amblyopia. CONCLUSIONS. The prevalence of amblyopia was similar, whereas the prevalence of strabismus was lower than in other populations.

The prevalences of myopia and astigmatism in young Singaporean Chinese children are high, but that of hyperopia is low. Age effects were observed for each refractive error category, but differences between the sexes were not significant. Age-related variation in myopia prevalence may be influenced by ocular development, environment, and/or testability.