Prevalence of binocular anomalies among preschool children in Mashhad, Iran

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To determine the prevalence of binocular anomalies among preschool children in Mashhad, Iran


In a cross-sectional study with random cluster sampling, children aged 4 to 6 years old from kindergartens of Mashhad in Iran were selected. Examinations included: visual acuity, objective and subjective refractions, cover test, near point of convergence and stereopsis. Best corrected visual acuity worse than 8/10 or more than two Snellen lines difference between the eyes was defined as amblyopia. Anisometropia was defined as spherical equivalent refraction difference of 1.0 diopter and more between two eyes.


Of the 3765 selected children, 98.3% of them participated in the study. The mean age of the subjects was 5.09 (range: 4-6) years and 51.3% of them were boys. Strabiamus was found in 1.2 % of the children and intermittent exotropia had the highest prevalence. Prevalence of amblyopia and anisometropia were 0.5% and 6% respectively. Heterophoria was found in 62.7% and shift was toward esophoria.The mean near point of convergence was 5.09 ± cm. Stereopsis of 100 sec/arc and better was found in 94.6% of the subjects.


The results of this study indicated that the prevalence of strabismus was similar to other studies in Iran while there was a smaller prevalence of amblyopia. For preventing the incidence of binocular anomalies in children, a careful planning of the basic information is required to check the status of binocular vision.

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