Abstract
Amblyopia is a developmental disorder characterized clinically by decreased visual acuity in one eye that cannot be corrected with glasses; the fellow eye usually has normal visual acuity. Deficits on clinical measures of binocular vision, including stereoacuity are also common. Psychophysical measures have revealed 1) disruptions in motion perception, particularly at slow speeds, that affect both eyes, and 2) spared stereopsis for large disparities. Neuroimaging studies have implicated regions of the dorsal and ventral streams in both motion perception and stereopsis, but their shared processing has not been demonstrated. The aim of the current study was to determine whether behavioural measures of motion perception and stereopsis are correlated in typical or atypical vision. Accuracy on a stereoscopic depth discrimination task (0.2 – 3.5 deg disparity range), and coherence thresholds on global motion direction discrimination (0.3 – 30 deg/s dot speed) and motion-defined form orientation discrimination (0.1, 0.9, 5 deg/s dot speed) tasks were obtained from 369 participants (299 with healthy vision and 70 with amblyopia, age: 3–32 years). Visual acuity and stereoacuity were assessed using standardized tests. After controlling for age, significant correlations were found between stereoacuity and slow motion-defined form thresholds, and between small-disparity accuracy and slow global motion thresholds. Stereoacuity was shown to be a predictor, independent of visual acuity, of whether an individual has amblyopia. Overall, our results indicate an association between slow motion perception and fine stereopsis, suggesting a shared processing mechanism. There are also treatment implications; deficits in stereopsis and motion perception often persist following standard patching therapy for amblyopia. We hypothesize that these deficits contribute to treatment failure, to amblyopia recurrence, and possibly to the development of deficits in everyday activities such as hand-eye coordination and reading.
Acknowledgement: NSERC Discovery Grant Canada