Refractive Risk Factors for Amblyopia in Turkish Preschoolers: A School-Based Vision Screening Study of 1126 Children.

Purpose: To evaluate refractive risk factors for unilateral and bilateral amblyopia. Methods: In October 2019, 1126 preschool and primary school 1st grade students in Kozlu district of Zonguldak province underwent eye screening with a pediatric autorefractometer in a school environment. 125 children who were above the threshold values determined for refractive errors or for whom measurements could not be taken due to patient compliance were referred to us for eye examination. The referred children underwent a comprehensive eye examination. Amblyopia risk factors were analyzed with a logistic regression model. Results: Of the 125 referred children 106 were examined comprehensively. Of those 99 were analyzed. A total of 30 amblyopic children were identified (Unilateral amblyopia n=20, bilateral amblyopia n=10). The prevalence of amblyopia was found to be 2.6%. In regression analysis, presence of <2 D and 2-4 D hyperopia were found to be isolated risk factors for amblyopia (p<0.05). Astigmatism was a risk factor unilateral and bilateral amblyopia in univariate analysis (p=0.001, p=0.001 respectively). Incrementing values of anisometropia did not influence the development of amblyopia. However, the incidence rate of amblyopia increased in the incrementing diopters of anisometropia (11.4% at 0.5 D and below, 25.9% at 0.5-1 D range, 54.5% at 1-2 D range, 100% for 2 D and above). Myopia association with amblyopia was not statistically significant. Conclusion: We found lower than the generally accepted threshold values of hypermetropia, astigmatism and anisometropia to be risk factors for amblyopia. Our data can help shape threshold values and screening policies for refractive errors. More population-based studies are needed in different regions of our country in order to make guidelines consisting of optimal threshold values that can be used in amblyopia screening programs.