Binocular counterrolling during sustained body tilt in normal humans and in a patient with unilateral vestibular nerve section.

Two normal persons and a patient with unilateral vestibular nerve section were held motionless for ten minutes in the upright position, at 60 degrees tilt right ear down, and at 60 degrees tilt left ear down. In addition, one normal subject was held for ten minutes at each of 30, 60, and 90 degrees tilt left ear down. Photographs were taken of both eyes every ten seconds. Measurements of ocular counterrolling during these trials revealed torsional eye movements in all positions, including the upright, even though the head and body were stationary. Variations in torsion in the upright position ranged up to 2.75 degrees. At the tilt positions, variations ranged up to 4 degrees. Disconjugate movements were seen in all subjects in all positions. There were no significant differences in measurements of ocular counterrolling during static tilt between the normal subjects and the patient with the vestibular nerve section, in contrast to measures obtained during slow velocity dynamic testing.