BINOCULAR ENHANCEMENT OF THE VISUAL-EVOKED POTENTIAL IN PATIENTS WITHDUANES-SYNDROME

Monocular and binocular visual evoked potentials were recorded in eigh t patients with Duane's syndrome who used an abnormal head posture to maintain binocular single vision. With their abnormal head posture, al l patients had stereoscopic vision, although with mildly reduced stere oacuity, and the visual evoked potential showed binocular enhancement (mean binocular to monocular ratio, 1.44). Without their head posture, the patients experienced diplopia or suppressed vision in one eye. Bi nocular visual evoked potentials recorded under these conditions were of lower amplitude (mean binocular to monocular ratio, 1.05). However, without the abnormal head posture, a manifest strabismus was present and the deviating eye was not fixating the stimulus screen. Monocular visual evoked potentials recorded with the eye fixating just to one si de of the screen gave little or no response, and this lack of fixation may account for the loss of binocular enhancement of the visual evoke d potential in strabismus.