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Luminita Tarita-Nistor, Taylor Brin, Esther G Gonzalez, Graham Eric Trope, Martin J Steinbach; Disruption of binocular rivalry processes in patients with mild glaucoma. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2837.
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© ARVO (1962-2015); The Authors (2016-present)
Glaucoma affects neural structures in the visual system beyond the retina. Recent imaging reports indicate neurodegeneration of the corpus callosum—a deep neuronal bundle that connects the two brain hemispheres. Its dysfunction should be evident during binocular rivalry. The purpose of this study was to test binocular rivalry processes in patients with mild glaucoma and age-matched controls. We hypothesize that there is a disruption in alternation rates and in stimulus dominance in the glaucoma group relative to age-matched controls.
Thirteen patients with mild glaucoma (mean age 68 ± 6 years) and 12 age-matched controls (mean age 63 ± 6 years) participated. All subjects underwent a thorough visual assessment including visual acuity, standard perimetry, and optical coherence tomography. Then they participated in 4 one-minute-long psychophysical tests designed to measure binocular rivalry. The stimuli were orthogonal gratings with a spatial frequency of 0.5 c/deg and a size of 10 x 10 deg, presented on a computer screen and shown dichoptically through a double-mirror stereoscope. The participants pressed different buttons of a button-response box when they perceived only one orientation, the other, or both. Alternation rates and stimulus dominance were recorded.
The retinal nerve fiber layer was significantly thinner (p < .05) and the cup-to-disc ratio significantly higher (p < .05) in the glaucoma group versus the control group, but the standard perimetry results were comparable. Visual acuity (monocular and binocular) was normal in both groups, although it was significantly better in controls than in patients. For example, mean binocular acuity in control group was -.06 ± .08 logMAR and in the glaucoma group .02 ± .07 logMAR.The difference in exclusive dominance of the stimulus presented to the right and left eyes was small for controls (mean 5.5 ± 3s) and significantly higher (p = .003) for the patients (mean 18.2 ± 12s). The mean alternation rate was 9 ± 2 times/min for the control group, but the patients appeared to have two distinct responses: one (n = 2) with very high rates (mean 17 ± 1 times/min) and another (n = 11) with significantly lower rates (mean 6 ± 3 times/min) than controls (p = .02).
The results show major differences in rivalry responses between the glaucoma and control groups which may indicate dysfunction of the inter-hemispheric transfer of visual information.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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