Stability of retinal correspondence during divergence: evaluation with afterimages and Haidinger brushes.

Retinal correspondence has been described as invariant during normal binocular vision. However, there is substantial evidence that casts doubt on this interpretation and implies that retinal correspondence varies under certain conditions. This article reports the results of two experiments that appraise the stability of correspondence during fusional vergence in persons with normal binocular vision. In the first experiment, afterimages stimulated vertically corresponding retinal meridians prior to divergence. Three of six subjects gave data that indicated a change in the afterimage alignment significantly different from chance. The second experiment determined corresponding retinal areas with Haidinger's brushes. When divergence was maximally maintained, all six subjects who could appreciate the low-contrast Haidinger's brushes on the randomdot background saw two brushes while stereopsis and fusion remained present. Increases in plus lens power increased estimated brush separation.