LXIII A Comparison of Ocular Counter-Rolling Movements between Normal Persons and Deaf Subjects with Bilateral Labyrinthine Defects

Publisher Website
Google Scholar
Abstract
Ocular counter-rolling as a function of head (body) tilt in the frontal plant was measured in nine healthy persons and ten deaf subjects with bilateral loss of function of the semicircular canals; the functional status of the otoliths was unknown. A photographic technique was used taking advantage of natural landmarks on the iris which ensured a high degree of reliability in measuration. Measurements of several photographs at each body position disclosed a small but significant variation in both groups of subjects which was interpreted as "instability" of torsional eye position; it was approximately the same upright as in the tilt positions (25[degree], 50[degree], and 75[degree] left and right). The findings in the normal subjects revealed a characteristic pattern of counter-rolling. Torsion as a function of tilt rightward or leftward was greatest in the first 25 degrees from the upright, less from 25 to 50 degrees where it usually reached peak value, and thereafter in most cases tended to reverse direction. There were significant right-left differences in some cases but not in others. The average maximum value (counter-rolling "index" CI, of otolith function) calculated as one-half the difference between right-left torsion, ranged from 286 to 465 minutes of arc. The findings in the L-D subjects did not disclose the characteristic pattern found in normal subjects in most instances, and the CI ranging from 30 to 176 minutes of arc, showed no overlap with the normals. In some instances, there was no definite evidence of counter-rolling, in others it was limited to one direction of tilt, and in still others there was a small but regular dependence of counter-roll with the successive increases in bodily tilt. The highly significant group differences must have been due to loss of function of the auricular sensory organs, and intraindividual differences in the L-D group are best explained by the presence of some residual otolith function.