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Kimberly Meier, Deanna Sell, Eric Seemiller, Deborah Giaschi, Laurie Wilcox, Rowan Candy; Reflexive vergence responses to absolute disparity stimuli in 3- and 5-year old children. Journal of Vision 2019;19(8):61. doi: https://doi.org/10.1167/19.8.61.
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Typical binocular vision requires both motor and perceptual operations: humans use vergence eye movements to align the two retinal images and then integrate the information in visual cortex. We know that the ability to make front/back depth-order judgements with short-duration stereoscopic stimuli is adult-like in children by age 5 years for large (diplopic) retinal disparities, but immature for small retinal disparities. The goal of the current study was to understand the relationship between motor and perceptual binocular function in the presence of misalignment of short duration retinal images (320 ms) for children with typically developing visual systems. Ten five-year-olds and ten adults were presented with a zero-disparity fixation plane, followed by a 2.2 deg wide stimulus with binocular disparity (ranging between +/− 16 deg). In one condition we assessed the perception of diplopia, and in another we recorded vergence eye movements. Ten 3-year-olds participated in the eye movement recording condition. We found that the perceptual fusional range was larger in 5-year-olds (3 deg) than it was in adults (1 deg). Further, the latency of the vergence response was shorter in adults than in children, but the velocity of the response was similar for all ages, with the most robust responses for disparities of 2 deg and smaller. Thus, reflex vergence responses are consistent with reports of single vision by age 5, and 3-year-olds demonstrate reflex vergence responses over a similar range of disparities. These data have important implications for the development of amblyopia and strabismus during this preschool period.
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