Estimation of the position of the center of the fovea relative to fixation in normal subjects and in patients with amblyopia. Use of the visually evoked potential.

A new method to measure eccentric fixation based on differences in the wave-forms of visually evoked potentials to stimuli presented to different parts of the visual field was studied in ten normal and 13 amblyopic subjects. In all of the 20 normal eyes, fixation corresponded to the horizontal position of the center of the fovea within the resolution of the method, approximately 30 minutes of arc. In seven of the 13 amblyopic eyes, fixation did not correspond to the horizontal position of the center of the fovea. Only one of these amblyopic eyes was found to have eccentric fixation by visuscopy. The vertical position of fixation relative to the center of the fovea was not well defined by the method in either the normal or the amblyopic eyes.