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Joanne Malek, Cristi Llerena, Benjamin T. Backus; Stereoacuity Practice In Children And Adults. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4870. doi: https://doi.org/.
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The child’s visual system is usually more plastic than the adult’s. Fendick and Westheimer (Fendick and Westheimer, Vision Research 1983) reported 23-73% improvement in foveal stereoacuity thresholds in two adults. We aimed to determine whether improvement in stereoacuity (disparity thresholds) that occur over time with practice occur at different rates in children and older adults.
Data were collected from ten older adults (mean age: 59.3 ± 14.7) and ten children (9.1 ± 0.9) using a two alternative forced choice task, where disparity was controlled by a 2 down 1 up psychophysical staircase procedure. Participants were screened for visual acuity (>20/60 in each eye) and stereo vision (qualitative Randot). Each subject participated in four sessions (35-60 minutes each), 320 trials per session. The task required reporting which of two rectangles (6 cm wide and 12 cm tall, vertically separated by the width of an occluding bar, a gap of 1.5 cm, with a total display time of 1 second per trial) appeared closer. After the response a "yoked" feedback trial was presented that had the same disparity but also an occlusion (overlap) cue. There was no other feedback.
Two adults and three children could not reliably see depth in the stimulus and were excluded. Performance was close to 100% correct on feedback trials. 12 out of 15 participants showed a significant improvement in stereoacuity across sessions, but there was no statistically significant difference between children and adults.
Our study employed a larger group of participants, from the general population, than previous studies of perceptual learning for stereoacuity. We confirmed that improvement occurs with practice in normally sighted individuals, as was also recently reported for stereoblind subjects (Ding and Levi, PNAS 20l11). This finding could be useful to clinical rehabilitation of binocular vision following strabismus surgery. Differences between individuals accounted for much of the variance in our study.
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