Binocular treatment of amblyopia: from the laboratory to clinical trials

Over the last 10 years, numerous psychophysical studies have indicated that binocular mechanisms are structurally intact but functionally suppressed in amblyopia (1-8). Many of these studies have used a contrast balancing approach, whereby the contribution of each eye to binocular vision is equated or “balanced” by presenting higher contrast stimulus elements to the amblyopic eye than the fellow eye (6). Using this approach, the strength of suppression can be quantified by measuring the magnitude of interocular contrast difference required for normal binocular combination. When suppression strength has been correlated with other clinical measures, stronger suppression has been associated with worse stereoacuity and worse amblyopic eye visual acuity indicting a link between the monocular and binocular deficits in amblyopia (5,7).