Abstract
Purpose :
Purpose: In previous studies, we observed that amblyopes present deficits in motion extrapolation and motion extrapolation correction. However, we attributed those to two different mechanisms: a global horizontal connectivity defect for the extrapolation, and a low-level delay of the amblyopic eye information processing for the correction. To reconcile those results, we wanted to test amblyopic motion extrapolation and correction for extrapolation using a paradigm which involves these two mechanisms: the High-phi illusion. In the High-phi illusion, an annulus with a random texture (the inducer) rotates and will be suddenly replaced by uncorrelated textures (the transient), leading to the perception of rotational motion in the same or opposite direction depending on the duration of inducer.
Methods :
Methods: Ten adults amblyopes and 10 control subjects were tested monocularly in a two-alternative forced choice High-phi jump task where they had to report the direction of the perceived motion of the transient. Two spatial frequencies (SF) were tested: low (0.7 c/d) and high (2.8 c/d). In addition, control subjects were tested in reduced luminance conditions with different neural density filters. A double logistic function was used to fit the data. The point of subjective equality (PSE) of the drop curve characterized the point where the subject would give 50% same direction and 50% opposite direction response.
Results :
Results: Compared to low SF, the high SF condition exhibited a larger PSE in both control (P < 0.001) and amblyopic (P = 0.005) groups. In the high SF condition, the PSE for the amblyopic eye was significantly larger than the non-dominant eye of controls (P = 0.002), but there was no difference between the fellow eye and the dominant eye (P = 0.096). We also found a larger PSE in the amblyopic eye than in the fellow eye (P = 0.012). However, there was no significant difference of PSE under the low SF condition neither between the two groups nor between the eyes. In addition, we observed that the PSE increased when luminance was decreased at both low (F2,18 = 79.5, P < 0.001) and high SF (F1.2,11.1 = 28.6, P < 0.001).
Conclusions :
Conclusion: Our observations confirm an abnormal interaction of motion extrapolation and correction mechanisms specific to the amblyopic eye which may be due to a visual processing delay.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.