Regaining Visual Acuity Does Not Restore Motion Extrapolation Deficits in Amblyopia.

Purpose: We previously reported that amblyopes exhibit deficits in motion extrapolation and in correcting for overextrapolation. In this study, we explored whether these motion deficits remain when normal visual acuity is restored after successful standard treatment in adults with former unilateral amblyopia. Methods: Eleven clinically treated adult amblyopes and 11 control subjects participated in the study. We assessed visual motion processing functions by using two motion illusion paradigms: the flash-lag effect (FLE) and the flash-grab effect (FGE). We measured the monocular FLE and FGE magnitudes for all participants. Two contrast conditions (0.2 and 1) of FLE and two spatial frequencies (2 and 8 cycles) of FGE were tested. Results: Compared to controls, treated amblyopes still exhibited a smaller FLE magnitude at the 0.2 contrast (F1,20 = 5.69, P = 0.027) in both the former fellow eye (FFE) and the former amblyopic eye (FAE). Treated amblyopes had a larger FGE magnitude than controls (P ≤ 0.008) in both eyes, and the FGE magnitude of FAE was larger than that of FFE (F1,20 = 15.9, P = 0.003). The FLE and FGE magnitudes were significantly correlated in most conditions in controls (P ≤ 0.035) but not in treated amblyopia (P ≥ 0.201). Conclusions: We observed a smaller FLE and a larger FGE in treated amblyopes, suggesting that the motion extrapolation and the correction for extrapolation remain impaired in their brain. These may be due to processing delays and defective temporal integration from residual abnormal cortical connections in the amblyopic visual system.