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Akosua Asare, Kimberly Meier, En Cheng Chang, Conor Mulholland, Christopher Lyons, Laurie M. Wilcox, Deborah Giaschi; Coarse stereopsis prior to strabismus surgery is associated with post-surgical ocular alignment in children. Invest. Ophthalmol. Vis. Sci. 2022;63(7):3668 – A0325.
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© ARVO (1962-2015); The Authors (2016-present)
Depth information can be extracted from small retinal disparities (fine stereopsis) and from large disparities that give rise to diplopia (coarse stereopsis). Previously, we showed retrospectively that some children with strabismus have intact coarse stereopsis when fine stereopsis is disrupted, and these children have better ocular alignment after strabismus surgery. Here we describe a prospective study to assess three pre-surgical measures that may predict ocular alignment after strabismus surgery: fine stereopsis, coarse stereopsis, and global motion thresholds, all of which have been shown to be sensitive to disruption of binocular vision.
Eleven children aged 4-14 years were assessed before and 4-15 months after alignment surgery. Depth-discrimination accuracy (nearer/farther) was measured for cartoon characters relative to a 0-disparity reference frame. 3D stimuli were presented using shutter glasses, with disparities categorized as fine (0.02, 0.17, 0.67 deg) or coarse (2.0, 2.5, 3.0 deg), based on previous work. The stimuli were aligned for each child and presented 20 times per disparity in random order. Global motion direction-discrimination (left/right) coherence thresholds were measured using a staircase procedure. The clinical outcome measure was ocular alignment (prism diopters) after surgery.
Prior to surgery, depth-discrimination accuracy in the fine disparity range was near chance in all children regardless of post-surgical alignment. In the coarse disparity range, the association between pre-surgical depth-discrimination accuracy and post-surgical alignment was large (r = -0.65): children with higher accuracy showed smaller misalignment after surgery. For pre-surgical motion direction-discrimination, children with lower thresholds (better performance) showed smaller misalignment after surgery (r = 0.82). The association between coarse depth discrimination and motion direction discrimination prior to surgery was moderate (r = -0.47).
Our preliminary findings suggest that coarse, but not fine, stereoscopic performance may be useful for predicting ocular alignment outcomes after strabismus surgery. Coarse stereopsis matures before fine and may be important for coordinated binocular eye movements. Future research will determine if pre-surgical global motion perception provides independent information for predicting alignment outcomes.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.
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