Fusional responses of strabismics to foveal and extrafoveal stimulation.

Horizontal fusional responses of 11 strabismics, with normal or anomalous retinal correspondence, were studied. These included four small-angle esotropes with amblyopia, one intermittent esotrope (overcorrected intermittent exotrope), two intermittent exotropes (preoperative esotropes), one accommodative esotrope, and three microtropes with amblyopia. Fusional stimuli (with a constant accommodative demand) ranging from very small, central stimuli to those that cover the central, the peripheral, and both the central and the peripheral visual fields were used. All 11 strabismics produced fusional vergence responses. Many of the fusional responses included large nonmotor components. Small central stimuli were not effective in producing fusional vergence, whereas stimuli that covered the visual periphery produced fusional responses that were similar to those by subjects with normal stereoscopic vision.