Effect of induced dynamic aniseikonia on fixation performance during oblique gaze

This is a sequel to other papers dealing with the effect of induced aniseikonia and optical anisophoria on fixation eccentricity during bifixation. To stimulate the effect of induced anisophoria, controlled amounts of differential prism were induced in the vertical meridian. At the same time, stimuli were presented at various angles from the subject's straight ahead orientation. As demonstrated in other studies, it was found that a vertical prismatic difference will cause the eyes to fixate slightly eccentrically in the horizontal meridian. The eccentricity was measured with the border enhancement method, described and tested in other studies. In addition, it was found that the fixation deviation is increased further by oblique gaze, the greatest obliquity having the greatest effect. It was also found that whereas short-term adaptation reduces the prism effect somewhat, it has less influence on the effect of oblique gaze. In general, the study demonstrates the potential oculomotor problems inherent in optical anisophoria.