Risk factors for amblyopia

Purpose: To evaluate risk factors for unilateral amblyopia and bilateral amblyopia. Materials and Methods: In October 2019, a total of 1126 pre-school children and 1st grade elementary school students were scanned with a pediatric autorefractometer in Zonguldak Province, Turkey. 125 children whose refractive errors either above the predetermined levels or unable to be measured were sent for a comprehensive eye examination. The referred children underwent comprehensive eye examination. Those detected with amblyopia risk factors were analyzed using the multivariate 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 3.1%. In regression analysis, <2 D and 2-4 D hyperopia, <1 D, 1-2 D and ≥2 D astigmatism were isolated risk factors for unilateral amblyopia (p<0.05). When the value of anisometropia in incrementing diopters were evaluated, its relationship with amblyopia was not found to be significant. 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). Astigmatism was a risk factor unilateral and bilateral amblyopia in univariate analysis (p=0.001, p=0.001 respectively). Myopia association with amblyopia was not statistically significant. Discussion and 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.