Abstract: PURPOSE: A psychophysical paradigm involving parallax and lateral motion processing found that human motion perception is tuned by lateral motion. However, it is unclear whether deficits in dynamic stereo vision exist in amblyopes whose monocular vision has been fully normalized. Here we use a similar paradigm to investigate the dynamic stereoscopic vision in unilateral anisometropic amblyopia when normal visual acuity is restored.
METHODS: Twelve clinically treated subjects with anisometropic amblyopia (mean age 23.61 ± 3.00 years) with best-corrected visual acuity ≤ 0.1 logMAR, 8 non-amblyopic anisometropes (mean age 22.22 ± 2.57 years), and 12 age-matched emmetropes (mean age 23.38 ± 2.81 years) with normal vision participated in this experiment. We presented 50 moving Gabor elements with a spatial frequency of 3 c/d as visual stimuli to measure the stereoscopic performance at six motion speeds (0.17°/s, 0.33°/s, 0.67°/s, 1.33°/s, 2.67°/s, and 5.33°/s). During the experiment, the six motion speeds were presented in a random order and the presentation time of the stimuli was set to 1000 ms. The stimuli were presented at two depth planes (25 Gabor elements were presented at the fixation plane and the other 25 Gabor elements were presented at an uncrossed disparity relative to the fixation plane). Observers were asked to report whether the Gabor elements in the front fixation plane were moving in the right or left direction without a time limit. We applied the staircase method to quantify the dynamic (lateral motion) stereo performance in the experiment.
RESULTS: There were significant differences in the stereo thresholds of emmetropes at different speeds (P = 0.001). There were also significant differences in the stereoacuity of subjects in the anisometropes at different speeds (P = 0.003), while the differences in stereo thresholds of treated amblyopes at different speeds were not significant (P = 0.054). There was a significant difference in stereo thresholds between the treated amblyopes and the emmetropes and anisometropes (P < 0.001). Two-tailed Spearman correlation analysis showed that the correlations between dynamic stereo thresholds and the degree of anisometropia in anisometropes were not significant for the five speeds (P > 0.05), except for 2.67°/s (P = 0.013), and the correlations between dynamic stereo thresholds and the degree of anisometropia for the six speeds were not significant in the treated amblyopes (P >0.05). The correlations between the dynamic stereo thresholds and the degree of anisometropia were not significant in the amblyopic group with normal vision recovery(P >0.05) In the emmetropes, the correlations between dynamic stereo thresholds and RDS thresholds for the six speeds were not significant (P >0.05); in the anisometropes, the correlations between dynamic stereo thresholds and RDS thresholds for the six speeds were not significant (P >0.05). The correlations between dynamic stereo thresholds and RDS thresholds in the six velocity conditions were also not significant in the treated amblyopes (P >0.05).
CONCLUSIONS: There is a deficit in dynamic (lateral motion stimulation) stereo vision in refractive parallax amblyopes with normal visual acuity after patching treatment.

Key words: anisometropic amblyopia, speed tuning function, binocular vision, dynamic stereopsis, lateral motion