Retinal input is continually perturbed by small eye movements during periods of visual fixation. Though it is known that visual percepts tend to fade when retinal image motion is eliminated, limitations in instrumentation and technique have prevented researchers from effectively addressing whether, during natural viewing, fixational eye movements have any function beyond preventing fading.;To overcome past methodological obstacles and investigate the role of fixational eye movements in fine spatial vision, a new means of high-precision visual psychophysics was developed. A thorough survey of the capabilities of this system, dubbed EyeRIS, leveraging psychophysics and computational simulations, effectively demonstrates a robust and flexible real-time system for gaze contingent display and experimentation.;Using EyeRIS, subjects' acuity of visual discrimination was explored in a forced-choice task by employing retinal stabilization to rigorously compare perception in the presence and absence of fixational motion. It was discovered that performance was significantly degraded when the influence of fixational eye movements was removed in the discernment of high, but not low frequency stimuli. These findings support a critical role for fixational eye movements in fine spatial vision.
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