Abstract
Goal. Amblyopia is a neural developmental disorder characterized by a decrease in visual acuity and contrast sensitivity. Microsaccades are thought to play an important role in visual perception (e.g., enhancing visual acuity). Only one quantitative study (Shi et al., 2012), and one qualitative study (Ciuffreda et al., 1979) have examined microsaccades in amblyopia. Both reported that, under conditions of passive visual fixation –i.e., no visual stimulation other than fixation and no perceptual discrimination– microsaccade rate is suppressed. Purpose. To examine whether, under conditions of active visual fixation –i.e., visual stimulation and perceptual discrimination– the rate of microsaccades is suppressed in amblyopia. Methods. Thirteen amblyopic observers (8-strabismic, 5-anisometropic) and 13 age-matched controls were tested monocularly (amblyopic or fellow eye, left or right eye, respectively). Four Gabor patches appeared along the vertical and horizontal meridians and observers discriminated the orientation of a post-cued Gabor. Task difficulty was equated between eyes and across observers by adjusting stimulus contrast. Eye position was monitored at 1000 Hz. A standard velocity-based detection algorithm was used to detect microsaccades. Results. The peak velocity and amplitude of microsaccades in the amblyopic eye were significantly greater than those of fellow and control eyes, consistent with previous research (Shi et al., 2012). Both groups demonstrated the hallmark biphasic response (i.e, suppression followed by enhancement of microsaccade rate) following visual stimulation. In contrast to previous research (Shi et al. 2012; Ciuffreda et al., 1979), the microsaccade rate of observers with amblyopia was, overall, greater than that of control observers. Conclusion. The present results indicate that the microsaccade rate in amblyopia is not suppressed overall, but rather is enhanced relative to the control eyes. We are currently evaluating whether the increased rate of microsaccades is a compensatory mechanism of visual perception.
Meeting abstract presented at VSS 2015