Motion in depth perception of strabismic patients

Abstract

Purpose: In strabismus clinics, stereoscopic depth perception is usually examined with static stimuli. However, ability of perceiving motion in depth cannot be accessed with the method. We compared detectability of motion in depth for strabismic patients with the ability of static depth perception with a conventional stereo test. Experiment: To investigate the motion in depth perception of patients, we used random dot stereograms that represented a rotating cylinder. The upper and lower parts of the cylinder rotated in the opposite directions from each other and the patients were asked the location of the border between the two parts. Threshold disparity ( between the nearest and farthest points of the cylinder) was defined as the disparity which gave a critical level of performance with the method of limit. As a conventional stereo test with static stimuli Titmus stereo test was used. The measurement was performed for fourteen strabismic patiants from 4 to 38 years old.Results: The correlation between the result of the stereo motion test and that of Titmus stereo test was poor. For example, ability to perceive motion in depth was revealed (disparity threshold < 2.5 min of arc) for two of the patients who was not able to detect depth in static stimuli (0/9 for Titmus circle). The results suggest that the process for the dynamic aspect of binocular depth perception is preserved for some of the strabismic patients who lack static stereopsis. Conclusion; The results showed the importance of testing the ability for motion in depth perception (as well as for static depth perception) to assess the stereopsis of strabismic patients.