Clinical Testing of Cyclodisparity–induced Slant Perception with the Major Amblyoscope

Abstract

Abstract: : Purpose: To determine the validity and usefulness of a clinical method to investigate disorders of 3–D spatial perception associated with cyclo–torsional strabismus. Methods: A vertical line (31.0 x 0.4 degrees) with binocular cyclodisparities that ranged from 0 to 10 degrees was randomly presented to 17 healthy subjects with the major amblyoscope, Synoptophore (Clement Clarke Ltd., USA), and the perceived slant of the line in the pitch plane was evaluated by the matching method. The range of the cyclodisparities that give a subjective fronto–parallel plane was separately measured using the method of limits. Results: An incyclo–disparity induced top–forward, while an excyclo–disparity induced top–away slant perception. The maximal slant angle of the vertical line was 35 degrees on average at a cyclodisparity of 10 degrees, and the mean slant gain (perceived angle / geometrically calculated angle) was 64±13%. The range of cyclodisparities that give a subjective fronto–parallel plane was ±1.0 degree. The repeatability of the gain and the cyclodisparity measures was ±24% and ±1.0 degree, respectively. Conclusions: Slant perception induced by binocular cyclodisparities was reasonably assessed with the major amblyoscope. The narrow range of cyclodisparities that give a subjective fronto–parallel plane indicates that a considerable number of patients with cyclo–vertical strabismus may have distorted 3–D spatial perception when they achieve binocular fusion.

Keywords: binocular vision/stereopsis • strabismus • space and scene perception