Disconjugate and conjugate adaptation of saccades in a patient with presumed bilateral MLF syndrome

Abstract

Saccades of a patient with presumed bilateral MLF syndrome, who enjoyed good binocular alignment, were recorded before and after habitual monocular viewing. In the right eye, the gain of the rightward saccade was much larger than 1, while that of the leftward saccade was much smaller than 1.The saccadic gain of the left eye was 0.9 in both horizontal directions, which indicated that the saccadic system was mainly adjusted to the left eye. Despite the dysmetria of the right eye, binocular fusion was attained early after these saccades. The gains of each eye and the vergence angles early after the horizontal saccades changed significantly after habitual monocular viewing. Analysis of these results demonstrated that the conjugate adaptation to the left eye was modified by the disconjugate ocular motor adaptation mechanism in order to attain good binocular fusion early after the saccade. Disconjugate adaptation had limitations in overcoming the binocular disparity which was produced during the paretic saccade. The residual disparity was nullified by the disconjugate drift that followed the saccade. Some part of the drift was suggested to come from the disconjugate adaptation. These adaptational changes may be found in other patients with MLF syndrome who maintain good binocular alignment.