Perceptual Grouping During Binocular Rivalry in Mild Glaucoma

Published on May 25, 2022

Imagine your eyes doing a dance, trying to make sense of the world around you. That’s what researchers did in a study on patients with mild glaucoma. They wanted to understand how the brain processes visual information when there is damage to the optic nerve. They used a technique called binocular rivalry, where participants viewed different images with each eye and their brain had to decide which image to focus on. They found that both the glaucoma group and the control group were able to group similar images together, but there were some differences between the two groups. The control group had higher rivalry rates and longer periods of exclusive dominance for grouped images in certain conditions. This suggests that patients with mild glaucoma may have subtle impairments in their ability to perceive visual information, which could have implications for tasks like recognizing objects or understanding scenes. Further research is needed to fully understand these deficits and how they affect higher-level visual processing.

PurposeThis study tested perceptual grouping during binocular rivalry to probe the strength of neural connectivity of the visual cortex involved in early visual processing in patients with mild glaucoma.MethodsSeventeen patients with mild glaucoma with no significant visual field defects and 14 healthy controls participated. Rivalry stimuli were 1.8°-diameter discs, containing horizontal or vertical sine-wave gratings, viewed dichoptically. To test the grouping, two spatially separated identical stimuli were presented eccentrically to the same or different eyes and to the same or different hemifields. The outcome measures were the time of exclusive dominance of the grouped percept (i.e., percept with synchronized orientations), the rivalry rate, and the epochs of exclusive dominance.ResultsFor both groups, the grouping occurred primarily for the matching orientations in the same eye/same hemifield (MO SE/SH) and for the matching orientations in the same eye/different hemifield (MO SE/DH) conditions. Time dominance of the grouped percept of the glaucoma group was similar to that of the control group in all conditions. The rivalry rates in the MO SE/SH and MO SE/DH conditions were significantly larger in the control group than in the glaucoma group. The epochs of exclusive dominance of the grouped percept in the MO SE/SH condition were a median of 48-ms longer for the control group, but a median of 116-ms shorter for the glaucoma group when compared to those in the MO SE/DH condition.ConclusionPatients with mild glaucoma show clear impairments in binocular rivalry while evidence for deficits in perceptual grouping could be inferred only indirectly. If these deficits truly exist, they may have implications for higher levels of visual processing, such as object recognition and scene segmentation, but these predictions remain to be tested in future studies.

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