The prevalence of functional amblyopia and its related risk factors in preschool children in North-Eastern Iran.

Background: Purpose was to determine the prevalence of amblyopia and its related risk factors in children aged 3-6 years in Bojnurd, north-eastern Iran.

Materials and methods: In this cross-sectional study, from 12,331 children aged 3-6 in Bojnurd, 6600 children participated in annual amblyopic screening program and among them, around 1100 suspected cases were referred for full ophthalmic examinations. Measurement of visual acuity, cycloplegic refraction, subjective refraction, and cover test were performed for all participants. Amblyopia was defined as CDVA of 0.2 LogMar or less in each eye or 2-line difference or more in best-corrected visual acuity between two eyes.

Results: The prevalence of amblyopia was estimated 0.95% (95% confidence interval [CI]: 0.73%-1.2%). There was no relationship between amblyopia with age and genders. Most amblyopic children were hyperopic (61.9%; 95% CI: 48.7-73.8). Strabismus was found in 17.4% of amblyopic patients (95% CI: 9.05%-29.09%). Approximately half of the amblyopic children were anisometropic (55.5%; 95% CI: 42.40%-68.08%). The most common type of amblyopia was anisohyperopic (55.56%; 95% CI: 42.5%-67.5%). The prevalence of bilateral amblyopia was more than unilateral amblyopia. The assessment of data showed that hyperopia, astigmatism, and anisometropia were the most common causes of amblyopia in this study.

Conclusions: The prevalence of amblyopia was estimated about 1% in north-eastern Iran. Our study indicated a valuable information around the effect of refractive error and anisometropia on amblyopia which could be helpful in designing a comprehensive vision screening program for preschool children.