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Kimberly Meier, Brian Sum, Laurie M Wilcox, Deborah Giaschi; Sparing of coarse stereopsis in stereodeficient children depends on amblyogenic factors. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3091. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
We have shown that children with amblyopia and/or strabismus who routinely fail clinical tests of stereopsis which assess fused disparities (fine stereopsis) can perform as well as controls on laboratory tests using large disparities that give rise to diplopia (coarse stereopsis). This finding is consistent with the view that coarse stereopsis develops early in life before amblyogenic factors exert their full effect. Because disrupted binocular vision is often more common in amblyopia caused by strabismus than by anisometropia, the current study examined fine and coarse stereopsis as a function of etiological subtype.
Accuracy on a depth order judgment task was assessed in 58 children with anisometropic, aniso-strabismic, or strabismic amblyopia; strabismus without amblyopia; and controls. All patients were stereodeficient on the Randot Preschool clinical test. On each trial, participants viewed a dichoptically-presented cartoon character with crossed or uncrossed disparity and reported the depth sign relative to a reference frame. Stimuli were adjusted to correct eye misalignment. Three disparity ranges were assessed 1) small disparities (0.02-0.17 deg) within the range assessed by the clinical test, 2) disparities (0.33-1.0 deg) larger than those assessed in the clinical test but still fused, and 3) coarse disparities (2.0-3.5 deg) that give rise to diplopia.
There was an effect of subtype in each of the three disparity ranges (p < .01). In the smallest range, controls performed better than all subtypes (p < .038). In the middle range, controls performed better than the three strabismus subtypes (p < .001); the anisometropic group did not perform differently from other groups (p > .10). In the coarse range, only the aniso-strabismic group performed significantly worse than controls (p = .046). The latter subtype performed at chance on all three disparity ranges (p > .18), suggesting these children have no access to stereoscopic information at any scale. Performance in patients was not correlated with interocular acuity differences (p > .25).
The sparing of coarse stereopsis in stereodeficient children varies as a function of the etiological subtype. In particular, coarse stereopsis may be absent in children with ansio-strabismic amblyopia. This is not due to the depth of amblyopia, but may depend on other clinical variables such as age of onset of the amblyogenic factors.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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