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Anna Kosovicheva, Emily Wiecek, Melanie Kazlas, David G Hunter, Peter J Bex; Modulation of stereopsis and sensory eye dominance by gaze direction in strabismus. Invest. Ophthalmol. Vis. Sci. 2020;61(7):1730.
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© ARVO (1962-2015); The Authors (2016-present)
Previous work has shown that gaze direction influences sensory eye dominance and stereoacuity in normally-sighted observers. On average, stereoacuity is highest for straight-ahead gaze (Schreiber et al, 2001) and observers show greater right-eye dominance at rightward gaze directions (Khan & Crawford, 2001), which could be attributed to interocular differences in retinal image size (Banks, Ghose, & Hillis, 2004). We examined whether patients with strabismus show comparable changes in binocular function at different gaze directions, and whether these variations in eye dominance and stereopsis are correlated with one another.
We estimated sensory eye dominance and stereoacuity with bandpass spatial frequency filtered targets (SFpeak 3 c/deg) at seven gaze directions (-18° to +18° horizontally and -12° to +12° vertically, relative to primary gaze) in 5 observers with strabismus (5 - 45 prism diopters) and 6 normally-sighted controls (ages 6- 53). Eye dominance at each location was estimated by measuring the interocular contrast ratio (ICR) of a pair of dichoptic bandpass optotypes that produced perceptual reports of each optotype with equal frequency (Kwon et al., 2015). Stereopsis thresholds were measured as the disparity at which subjects identified a front-depth bandpass ring target with 80% accuracy in a 4-alternative forced-choice task.
Controls showed greater right-eye dominance for rightward gaze directions, consistent with previous findings. Based on linear fits to control observers’ ICRs at each location, the average change was +0.14% ± 0.05% contrast per degree of horizontal gaze change. Observers with strabismus showed greater variability in eye dominance (-2.83 %/deg to +0.25 %/deg), with some participants showing greater left-eye dominance for rightward gaze directions. In addition, gaze directions with greater sensory imbalance (i.e., more skewed ICRs) were not associated with poorer stereo performance across all observers (Pearson’s r = 0.11 p = 0.46).
In observers with strabismus, variation in sensory eye dominance at different horizontal gaze directions cannot be explained solely by changes in retinal image size. In addition, within observers, variations in stereopsis thresholds can be dissociated from variations in eye dominance at different gaze directions, indicating that these tasks measure different functional endpoints.
This is a 2020 ARVO Annual Meeting abstract.
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