Correlation between Visual Acuity, Contrast Sensitivity and Depth of Vision before and after Partial Time Occlusion Therapy in Strabismic and Anisometropic Amblyopes

Abstract

Background Amblyopia is known as the visual developmental disorder that follows selective disruption of the visual input to one eye early in life. It is considered the second most common cause of decreased visual acuity in both children and adults affecting greatly both economic and social life. It affects most of the visual parameters, so great efforts are carried out in developing effective methods controlling different deficits in amblyopia, being a great concern for all the society. However, monocular occlusion therapy remains the easiest and most popular way despite that there are many doubts in its reliability in controlling visual abnormalities other than acuity. Purpose To compare the different performance of anisometropic and strabismic eyes with moderate amblyopia, using partial occlusion therapy regarding visual acuity, contrast sensitivity and depth of vision. Methods Forty-nine children between 7 and 12 years old suffering from moderate amblyopia were classified into two groups: 25 anisometropic amblyopes and 24 strabismic ones. Two hour occlusion regimen with near activity was conducted by patients, assured by parents monitoring. Evaluation of visual acuity, contrast sensitivity and stereoacuity was conducted at each visit throughout the treatment regimen which was continued for 6 months on monthly follow up basis. Results Children in both groups improved significantly in visual acuity. There was a considerable difference among the distribution of improvement within each group where 9% of strabismic amblyopes achieved full visual recovery as compared to 40% in the anisometropic group, and 62.5% had residual amblyopia as compared to 36% in the anisometropic one, in spite of no significant difference of average improvement between groups (<0.0001). Only 42% of the strabismic amblyopes improved in stereoacuity as compared to 88% of the anisometropic ones, however, the difference in mean improvement was not significant between the two groups. Conclusion Children with moderate anisometropic or strabismic amblyopia 7-12 years old, can get considerable benefits from part time occlusion therapy in different visual aspects. The anisometropic amblyopes have better contrast sensitivity improvement and more reliable expectations of recovery being largely dependent on the initial visual acuity.