The Prevalence of Amblyopia and Strabismus among Schoolchildren in Northeastern Iran, 2011

To determine the prevalence of amblyopia and strabismus in the schoolchildren of the city of Bojnourd, Iran In 2010, randomized stratified cluster sampling was employed in a cross-sectional study on primary and junior high schoolchildren. All the examinations were performed in schools. All students received refraction, vision and subjective refraction tests. The cover test was used to determine tropia. Amblyopia was defined as best corrected visual acuity (BCVA) 20/30 or less or a 2-line interocular optotype acuity difference with no pathology. Of 2,020 selected students, 1,551 participated in the study (response rate: 76.7%). The prevalence of amblyopia was 2.3% (95% CI: 1.6-3.1); 2% of the male students and 2.5% of the female students had amblyopia (P=0.508). Amblyopia decreased significantly with age (P=0.032). The most common type of amblyopia was anisometropic followed by isometropic amblyopia. Hyperopia and astigmatism were the most common refractive errors in individuals with amblyopia. The prevalence of strabismus in the students was 2% (95% CI: 1.3-2.7). Of female and male students, 2.4% and 1.4% had strabismus, respectively (P=0.160). Of the students with strabismus, 67.7%, 25.8% and 6% had exotropia, esotropia and vertical deviations, respectively. The prevalence of amblyopia and strabismus in the current study was intermediate. However, correction of refractive errors at young ages can largely prevent amblyopia and strabismus in children.