Psychophysical measures of visual acuity in autism spectrum conditions

Previously reported superior visual acuity (VA) in autism spectrum conditions (ASC) may have resulted from methodological settings used (Ashwin, Ashwin, Rhydderch, Howells, & Baron-Cohen, 2009). The current study re-tested whether participants with (N = 20) and without (N = 20) ASC differ on psychophysical measures of VA. Participants’ vision was corrected before acuity measurement, minimising refractive blur. VA was assessed with an ETDRS chart as well as the Freiburg Visual Acuity and Contrast Test (FrACT). FrACT testing was undertaken at 4 m (avoiding limitations of pixel-size), using 36 trials (avoiding fatigue). Best corrected VA was significantly better than the initial habitual acuity in both groups, but adults with and without ASC did not differ on ETDRS or FrACT binocular VA. Future research should examine at which level of visual processing sensory differences emerge.