Ocular torsion position and the perception of visual orientation

Previous studies have shown that in patients with unilateral vestibular deafferentation (UVD) there is a close relationship between the change in ocular torsional position consequent on the UVD, and the visually perceived orientation of short dim lines in an otherwise darkened room (1). However that result may have been confounded because the UVD may have affected both ocular torsion and sensory information about head position re gravity which must be used in making the visual perceptual judgement. Therefore we have sought a means of testing the relationship between ocular torsional position and the visual perception of orientation which was not confounded by the possible effect of changes in perceived head position.