A Pilot Study on Amblyopic Children for Possible Quantification of the Left/Right Mismatch

Amblyopia is a childhood eye condition with low vision in one or rarely both eyes, due to suppression at the visual cortex, that persists after rectification of risk factor at eye level. For an amblyopic child, the visual inputs from the amblyopic eye (AE) is suppressed at the brain. This leads to reduced visual acuity and poor or complete loss of stereopsis. Conventional clinical tests such as Worth 4-dot test and Bagolini striated lens test can only detect the presence of suppression but cannot quantify the extent of suppression, which is important for quantifying and identifying the effectiveness of treatments for amblyopia. In this paper, we propose a possible cost-effective and child-friendly method for quantifying the level of ocular suppression in amblyopia. The procedure is based on the fact that for amblyopic subjects, there is an asymmetry in the amount of ocular suppression experienced by the AE and this suppression leads to an inferior performance of the AE in an image recognition task. Preliminary studies performed on six each of control and amblyopic subjects are presented in this paper. We have shown that the absolute value of the deviation of the ratio of accuracies of both eyes in an image recognition task from unity can be used as a measure of the suppression. Paired t-test revealed a significant difference between the means of the accuracies of amblyopic and fellow eyes (p=0.03) in the case of amblyopic subjects. Equivalence test done using `two-one-sided t-tests' procedure shows that the equivalence of the accuracies of left and right eyes for control is statistically significant (p = 0.008, symmetric equivalence margin of 5 percentage points).