3D shape perception in strabismus subjects

Abstract

AbstractPurpose To evaluate 3D shape perception in strabismus subjects, psychophysical experiment was performed using 3D shapes extracted from four different visual cues (shading, texture, motion and disparity), comparing normal and strabismus subjects.Methods The 11 randomly generated complex 3D shape visual stimuli were created and rendered in 4 modalities (3D shape from shading, texture, motion and disparity) and displayed on a PC monitor. The subjects were required to indicate the global maximum of the 3D shape as accurately as possible by displacing a red cross using the computer mouse. The distance in depth (cm) between the global maximum indicated by the subject and the true global maximum was calculated. Strabismus subjects (n=43; 6‐65 years of age) and normal subjects (n=18: 6‐57 years of age) participated in the task. All the subjects have normal or corrected normal visual acuity. Stereo acuity was also evaluated by titmus stereo test.Results 3D shapes extracted from disparity were more difficult to perceive than those extracted from texture (ANOVA, p<0.03), motion (p<0.01) and shading (p<0.01) in both normal and strabismus subjects. The 3D shape perception in normal and strabismus subjects differed only for the binocular stereopsis cue, not the other visual cues of motion, shading and texture. In addition, 3D shape perception of motion, shading and texture was not affected by the stereo acuity in either normal or strabismus subjects.Conclusion Even the strabismus patients with weak or no stereopsis can use other visual cues, such as motion, texture and shading to perceive 3D shape to the same degree as normal subjects.