Functional Amblyopia; A Blinding Disease in a Normal Eye

Amblyopia is reduction of vision with the proper optical correction either in one or both eyes.. The diagnosis of Amblyopia requires both the demonstration of visual acuity loss and the absence of an organic cause. A visual defect screening program was conducted on children aged 3-14 years of Bope-Poddala health unit area of the city of Galle Sri Lanka. Children aged 5-14 years were examined at each respective school. Children aged 3-5 years were examined at the pre schools .Children not attending to pre schools were examined in the community. All possitives and difficult to handle cases with a 10% of normal were referred to the ophthalmology clinic for secondary screening, investigation and diagnosis. Cases of diagnosed Amblyopia were called after one year for re-assessment. A total of 6685 school children and 934 preschool children were enrolled for this study. After exclusion, 5649 children were screened.Out of the total of 5649 children who were screened 439 (7.8%) were found to have eye diseases with or without visual defects giving a prevalence of 78/1000 children. Of those with such diseases, 88.8% had visual defects. The prevalence of visual defect was 6.9% (69/1000 children). Of the children with visual defects 90.0% (351) were due to refractive errors. The prevalence of refractive errors was 6.2% (62/1000 children).The analysis of the prevalence of different types of refractive errors showed that the prevalence of myopic astigmatism was 52.3%, Simple myopia was 24.6%, simple hypermetropia was 12.5%. Myopic astigmatism was the commonest type of refractive error in unilateral or bilateral involvement. The second commonest was simple myopia. It was found that out of 223 children with bilateral refractive errors 11.6% had unilateral Amblyopia and 17.5% had bilateral Amblyopia giving a total of 29.1%. Of all children with unilateral refractive errors 39.8% had Amblyopia. The development of Amblyopia among unilateral refractive errors was higher than bilateral refractive errors (p<0.05).The total prevalence of refractive Amblyopia was 2.1% of the population. Of them 1.4% had unilateral Amblyopia and 0.7% had bilateral Amblyopia. This difference was statistically significant. (P<0.05) Highest prevalence was observed in the age group of six and seven years (3.4% and 3.0%.). Distribution of Amblyopia among males and females were almost equal. The total prevalence of Amblyopia among children was 2.3%. Refractive Amblyopia calculated was 2.1% that consisted of 1.9% of Anisometropic Amblyopia.The strabismic Amblyopia was 0.2%. Deprivation Amblyopia was 0.2%. There were no Amblyopes found in the group of strabismic Amblyopia without refractive errors.