Motion Perception in Central Field Loss

Healthy peripheral retina is exquisitely sensitive to fast speeds. Individuals with central field loss (CFL) typically only have residual peripheral vision and studies suggest they become adept at using peripheral motion information, as in the case of vection (Tarita-Nistor et al. 2008). However, we showed that smooth pursuit in CFL is impaired across a range of speeds and visual acuity cannot explain this decrement in performance (Shanidze et al. 2016). Thus, the question remains whether this deficiency is due to oculomotor limitations, or a potential impairment of peripheral motion processing, as indicated by Eisenbarth et al. 2007. We compared the ability of CFL participants (6) and age-matched controls (3) to discriminate speed and direction of motion in a two spatial alternative forced-choice design. Participants fixated a central dot (0.5) and viewed moving dots on the left and right of fixation for 500 ms. (The central 2 vertical strip of the display was blank). The reference dots moved 45° clockwise of rightward at 5 or 10 °/s (in separate blocks). For speed discrimination, observers judged which interval had the faster test speed, and for direction discrimination they judged which had more clockwise test direction. We found no significant difference in mean velocity or direction discrimination thresholds of CFL participants and controls for either dot speed. Our results indicate that for 5-10 /s speeds, velocity and direction discrimination are intact in the periphery of individuals with CFL. Therefore, CFL participants’ deficits in smooth pursuit are likely not due to motion perception deficits.