Refractive Errors and Amblyopia in Children Entering School: Shahrood, Iran

Purpose. To determine the prevalence of amblyopia, strabismus, and refractive errors in children entering school. Methods. In this cross-sectional population-based study, 6-year-old children enrolling in Shahrood schools were randomly sampled. Those with organic blindness or mental retardation were excluded. Ocular alignment, visual acuity, stereopsis, cover testing, and cycloplegic refraction were recorded for all children by an optometrist. A diagnosis of amblyopia was based on a best-corrected visual acuity of 6/12 or less in one or both eyes, or a bilateral difference of at least two best-corrected visual acuity lines. Results. A total of 902 children were invited for optometry examinations, among which 827 (91.7%) responded and 815 children (98.5%) were included in the study. The prevalence of significantly reduced visual acuity (uncorrected VA <= 6/12 in either eye) and amblyopia was 3.6 and 1.7%, respectively. The prevalence of hyperopia (+2.00 D or worse), myopia (-0.50 D or worse), astigmatism (0.75 D or worse), and anisometropia (1.00 D or more) were 20.5, 1.7, 19.6, and 2.2%, respectively. Significant refractive error, defined as hyperopia >+3.50 D, myopia >-3.00 D, astigmatism >1.50 D in the orthogonal meridian or >1.00 D in the oblique meridian, or anisometropia (hyperopic >1.00 D, myopic >3.00 D) was detected in 2.1, 0.1, 5.0, and 0.9% of the sample, respectively. Strabismus was diagnosed in 1.2% of children. Overall, 52 children (6.4%; 95% confidence interval [CI], 4.7-8.1%) were at risk of amblyopia; of these, 81% had significant refractive errors, 11% had strabismus, and 8% had both. Conclusion. A considerable proportion of 6-year-old children have strabismus and/or significant, potentially amblyogenic refractive errors. The relatively high rate of hyperopia and astigmatism in the studied population needs more attention. The results of the study emphasize the need for adequate diagnostic and therapeutic eye care services for preschool children.