Abstract
Purpose:
We investigated the role of interocular luminance difference on supra-threshold binocular phase combination, from which we wanted to derive the functional balance index between the two eyes, for both normals and amblyopes. We also attempted to determine whether we can artificially simulate “amblyopic” behaviour in normal subjects and recover “normal” response pattern in amblyopic subjects by inducing luminance difference in the two eyes, and to understand the theoretical basis of such effects.
Methods:
Using a binocular combination paradigm developed by J. Ding and G. Sperling (2006) and neutral density (ND) filters of varied intensities, the effect of unilateral mean luminance on binocular combination in 3 normal and 4 amblyopic observers were quantified.
Results:
In normal observers, attenuation of one eye’s stimulus luminance with ND filters produces binocular combination similar to those of amblyopic subjects. Correspondingly, in amblyopic observers, reduction of the fellow eye’s stimulus luminance produces binocular combination similar to those of normal subjects. These results can be well explained by a modified contrast gain-control model, which suggests that decreasing the mean luminance in one eye reduces the efficiency of gain-control from that eye to the other eye, thus lower its contribution in binocular combination.
Conclusions:
Our manipulation of interocular luminance difference provides a simple and effective way to modulate interocular imbalances in amblyopia by reducing the effectiveness of the signal originating from the fellow fixing eye, which might bear upon any future binocular treatment of amblyopia.
Keywords: 417 amblyopia •
434 binocular vision/stereopsis •
473 computational modeling