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Kimberly Meier, Grace Qiao, Laurie M. Wilcox, Deborah Giaschi; Coarse stereopsis reveals residual binocular function in children with strabismus. Journal of Vision 2014;14(10):698. doi: https://doi.org/10.1167/14.10.698.
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Depth information can be extracted from small retinal disparities (fine stereopsis), or large disparities that give rise to diplopia (coarse stereopsis). Stereopsis for large disparities may be spared when stereopsis for small disparities is disrupted by amblyopia, possibly due to the early development of coarse stereopsis (Giaschi et al. 2013, J Vision). Here we extend these findings to include children with strabismus alone with no confounding visual acuity deficits. Further, we evaluate the link between stereopsis and eye alignment following strabismus surgery. Stereoscopic stimuli were presented using liquid crystal shutter glasses to children (4-12 years) with poor stereoacuity due to strabismus or strabismic amblyopia. The task was to indicate whether a cartoon character was nearer or farther than a zero-disparity reference frame. Test disparities were categorized as fine (0.02, 0.08, 0.17, 0.33, 0.67, 1.0 degrees) or coarse (2.0, 2.5, 3.0, 3.5 degrees) based on a preliminary diplopia assessment. A subset of children had undergone strabismus surgery and a retrospective chart review was performed to classify them as eyes-straight or eyes-misaligned, based on eye alignment one year post-surgery. Performance was similar in both groups of children, and matched that previously obtained from anisometropic and mixed amblyopia groups. In the coarse range, all groups of stereodeficient children were statistically indistinguishable from age-matched control children. However, the stereodeficient children showed significantly degraded performance in the fine range. Accuracy was higher in the eyes-straight group than in the eyes-misaligned group, particularly in the coarse range. Our results add to growing evidence that coarse stereopsis may be spared when fine stereopsis is disrupted, in this case from early visual deprivation due to strabismus. We propose that the coarse stereoscopic mechanism acts to keep the eyes aligned following surgery, and that it plays essentially the same role in the typical development of coordinated binocular eye movements.
Meeting abstract presented at VSS 2014
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