Human amblyopia: consequence of chronic interocular suppression.

In human strabismic amblyopes, visual acuity is selectively impaired in the central part of the visual field of the deviated eye. The acuity loss is usually asymmetric and depends on the direction and magnitude of the interocular misalignment. By contrast, in anisometropic amblyopes, the loss of acuity extends symmetrically in both the nasal and the temporal fields of the defocussed eye. Binocular interaction, including stereopsis, is selectively lost in the central part of the visual field of both strabismic and anisometropic amblyopes, but preserved in the periphery. For both groups of subjects, the areas of acuity and binocularity loss correlate well with the regions of interocular suppression. These findings support the idea that amblyopia arises at a central locus in the visual system, as a consequence of chronic interocular suppression.