Abnormal Monocular and Dichoptic Temporal Synchrony in Adults with Amblyopia

We investigate temporal synchrony within one eye and between both eyes in adults with amblyopia. Eight adult amblyopes (range, 19.88-27.81 years old; median, 22.86 years old) and 12 age-matched adults with normal vision (range, 21.2-50.30 years old; median, 23.78 years old) participated in the experiment. We showed two pairs of Gaussian blobs flickering at 1 Hz as visual stimuli, one pair with the same temporal phase modulation (i.e., the reference) and another pair with a distinct temporal phase (i.e., the signal). We employed the constant stimuli method to measure the minimum degree of temporal phase (temporal synchrony threshold), at which participants were able to discriminate the signal pair under binocular, monocular, and dichoptic viewing configurations. The temporal synchrony threshold was different across the six configurations (P = 0.001). There was also an interaction between the configuration and the group (P = 0.004). The synchrony threshold was significantly higher in amblyopes than in controls under the configurations where two pairs of blobs were presented to the amblyopic eye (136.52 ± 50.19 vs. 97.08 ± 22.02 ms, P = 0.027) and where the paired blobs were presented to different eyes (163.15 ± 80.85 vs. 111.61 ± 22.46 ms, P = 0.049). The visual deficits in these two configurations were significantly correlated (r = 0.824, P = 0.012). The threshold for detecting temporal asynchrony increased when the stimuli were presented only to the amblyopic eye and when they were dichoptically presented to the amblyopic and fellow eyes.