Optically induced eye torsion. II. Optostatic and optokinetic cycloversion.

Using a synoptophore and an objective photographic method, it was demonstrated that the eyes undergo a tonic cycloversion under the influence of a pattern with slanting stripes. A slight tilt with respect to the vertical had a greater effect than a tilt with respect to the horizontal. The maximum amplitude was of the order of 1 degree. This optostatic eye torsion is considered to be the optomotor analogue of the "ophthalmostatic" otolithic reflex. Optokinetic torsion was also investigated. To this end, rotating discs that were divided into sectors were presented in a synoptophore. The maximum amplitude observed in the 4 subjects was 6 degrees. Optokinetic torsion may be viewed as the optical superstructure above the semicircular canal reflex. Non-fusional cyclovergence, for which purpose counter-inclined or counter rotating contours were presented to both eyes, could not be demonstrated with certainty.