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Sarah J Waugh, Monika A Formankiewicz; Grouping of flankers is similar in children to adults and does not break crowding.. Journal of Vision 2019;19(10):119a. doi: https://doi.org/10.1167/19.10.119a.
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Spatial interactions, including lateral masking and crowding, affect clinical visual acuity scores. Magnitude of interaction is determined by taking the difference in acuity (logMAR) between a flanked versus an isolated letter. It depends on target-flanker separation, target-flanker similarity and flanker grouping. Grouping of flankers, or ungrouping of flankers from the target, also contributes to visual scene perception and could be different in children and adults. We examined the impact of target-flanker similarity and flanker grouping on single letter acuity in normal healthy children aged 3 to 11 years (n=155) and adults (n=32). Visual acuity was measured for isolated letters (HOTV) and single letters (HOTV) surrounded by a box, bars, black letters or red letters (CLUA), placed 1 stroke-width away. No statistically significant effect of age was found on magnitude of spatial interaction when bars or a box surrounded the target letter. Threshold elevation was greater (p< 0.001) for bars (0.15±0.01 logMAR) than a box (0.11±0.01 logMAR). When letters surrounded a black letter, the magnitude of spatial interaction reduced with age (p< 0.05). It was greater for black, than red, surrounding letters (p< 0.001). From 3–5 years to adulthood, threshold elevation fell from 0.27±0.03 to 0.18±0.02 logMAR for black surrounding letters, and from 0.22±0.03 to 0.15±0.02 for red surrounding letters. Grouping of flankers by colour or continuity reduces the magnitude of spatial interaction similarly for healthy young children and adults. In children, target-flanker similarity heightens spatial interactions, demonstrating crowding. Grouping by colour bends but does not break crowding, so could be used to improve visual attention in children without losing diagnostic potency.
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