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Matthew Roche, Brian Keane, Sabine Kastner, Thomas Papathomas, Steven Silverstein; Visual acuity differences within the normal range strongly alter visual perception: A cautionary tale for studies of special populations. Journal of Vision 2015;15(12):324. doi: https://doi.org/10.1167/15.12.324.
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© ARVO (1962-2015); The Authors (2016-present)
The majority of studies that examine visual processing in special populations ensure that subjects have normal or corrected-to-normal vision, without also reporting whether subject groups are matched on visual acuity (VA) within the normal range. This is problematic because many factors compromise VA (e.g., aging, schizophrenia) and optimal VA among healthy younger adults is better than 20/20. Therefore we ask: Do VA differences within the normal range alter visual performance? To consider the question, we measured binocular VA with a logarithmic eye chart, and compared healthy adults with 20/20 vision (N=13) to those with better-than-20/20 vision (SharpPerceivers, N=23) on three behavioral tasks. In the contour integration (CI) task, subjects located an integrated shape embedded in varying quantities of randomly-oriented noise elements; in the collinear facilitation task, subjects detected a low-contrast element flanked by collinear or orthogonal high-contrast elements; in the discrimination task, subjects discerned the orientation of four briefly-presented, high-contrast pac-man elements. The SharpPerceivers integrated contours under noisier conditions (p< .001), benefited more from collinear flankers (p< .05), had higher contrast sensitivity (p=.002) and discriminated orientation more accurately than the 20/20 group (p=.02). To verify that refractive error generated these results, 5 additional observers ran the above tasks, once with 20/20 uncorrected vision (logMAR=-.04) and once with optical correction (better than 20/20; logMAR=-.14). Even with this small sample, we found worse CI and lower contrast sensitivity when subjects were not wearing their corrective lenses (ps< .05). Therefore, previous studies reporting contour integration, collinear facilitation, contrast sensitivity, or orientation discrimination in aging, development, or mental disorders may need to be re-evaluated if they did not match for VA within the normal range. Our results also offer a surprisingly powerful explanation of individual differences and show that residual refractive error strongly alters visual performance for observers with 20/20 vision or better.
Meeting abstract presented at VSS 2015
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