Different patterns of retinal correspondence in the central and peripheral visual field of strabismics

We tested the state of retinal correspondence at different positions in the visual field of ten observers with strabismic and/or anisometropic amblyopia, four strabismic subjects with alternating fixation and three normal controls. Correspondence was evaluated by the subjective displacement of dichoptic stimuli; to estimate the displacement, we used red-green filters, Bagolini striated glasses, polarizing filters and a phase-difference haploscope. Strabismic observers (amblyopes and alternators) frequently showed variations in the angle of anomaly (ie, the amount of shift of space coordinates in the squinting eye) between different regions of the visual field. Correspondence tended to be closer to normal in the central field and more anomalous in the periphery. These findings cannot be explained by the progressive loss of localization sensitivity with increasing eccentricity. We suggest that the different patterns of retinal correspondence in the central and peripheral visual field of some strabismic observers might be due to a mechanism of selective stabilization of binocular connections in the peripheral visual field, where the larger corresponding areas overcome a limited misalignment of the eyes. In the central visual field, normal correspondence is preserved, and diplopia has to be prevented by interocular suppression.