Motion Misperception in Anisomyopia Before and After Optical Correction.

PURPOSE: To investigate interocular delay in anisomyopes at different spatial frequencies.

METHODS

Interocular delay (difference in processing speeds between eyes) was measured psychophysically in 21 anisomyopes (observers with a large refractive difference), 20 isomyopes, and 19 emmetropes at 0.5, 1, and 2 cycles per degree (c/deg). During the visual task, small Gabor elements with lateral movements were shown to both eyes. When interocular delay was present, the stimuli created an illusory percept of a cylinder rotating in depth (motion misperception) despite no depth cues. Anisomyopes and isomyopes were tested before and after optical correction; emmetropes were tested only before. Clinical differences between eyes in anisomyopes, including axial length, visual acuity, and spherical equivalent, were also measured.

RESULTS

Anisomyopes showed interocular delay at 2 c/deg, with the more myopic eye faster before optical correction (Cohen's d = 0.48), correlating with clinical differences (P < 0.05). Optical correction abolished this delay at 2 c/deg. At 0.5 and 1 c/deg, anisomyopes showed no delay before optical correction, although there were spatial differences between the eyes. Surprisingly, they showed interocular delay after optical correction (more myopic eye faster) when the images of both eyes were spatially equal (P < 0.05). Isomyopes and emmetropes showed no interocular delay at any spatial frequency before and after optical correction.

CONCLUSIONS

Anisomyopes experience motion misperception at 2 c/deg before optical correction and at 0.5 and 1 c/deg after correction, suggesting optical and neural origins of interocular delay. Tailored interventions based on clinical characteristics may help improve visual function such as motion perception.