Abstract
Glaucoma is considered a progressive optic neuropathy because of the damage and death of the retinal ganglion cells. It is also a neurodegenerative disease because it affects neural structures in the visual system and beyond, including the corpus callosum–the largest white matter structure involved in inter-hemispheric transfer of information. In this study we probed the dysfunction of the inter-hemispheric processing in patients with mild glaucoma using the phenomenon of binocular rivalry. Patients with mild glaucoma and no measurable visual field defects and age-matched controls underwent a thorough visual assessment. Then they participated in a series of psychophysical tests designed to examine the binocular rivalry derived from intra- and inter-hemispheric processing. Static horizontal and vertical sinewave gratings were presented dichoptically using a double-mirror stereoscope in 3 locations: centrally, to probe inter-hemispheric processing, and peripherally to the left or to the right, to probe intra-hemispheric processing. Although the two groups were matched in functional measures, rivalry rate of the glaucoma group was significantly lower than that of the control group for the central location, but not for the peripheral location. These results were driven mainly by the patients with normal tension glaucoma whose average rivalry rate for the central location (from which information reaches the two hemispheres) was almost half (46% lower) that of the controls. These results indicate a dysfunction in inter-hemispheric transfer in mild glaucoma that can be detected behaviourally before any changes in standard functional measures.
Highlights
Glaucoma is the second leading cause of blindness affecting more than 60 million people worldwide.[1]
The purpose of this study was to probe the integrity of the inter-hemispheric transfer using binocular rivalry in patients with mild glaucoma and no detectable deficits on standard functional measures
A diagnosis of mild glaucoma was made by an experienced glaucoma specialist and was based on 1) changes consistent with the diagnosis of mild glaucoma shown by consecutive clinical examinations of the status of the optic disc, 2) intraocular pressure level, and/or 3) a family history of Binocular rivalry in glaucoma glaucoma
Summary
Glaucoma is the second leading cause of blindness affecting more than 60 million people worldwide.[1] It is considered a progressive optic neuropathy because of the damage and death of the retinal ganglion cells (RGCs),[2] as well as a neurodegenerative disease because it affects neural structures in the visual system far beyond the retina.[3] Histopathological examination of the brain from patients with advanced glaucoma has revealed degeneration of the intracranial optic nerve, the lateral geniculate nucleus, and the visual cortex,[4] while neuroimaging studies have shown changes in the entire primary visual pathways
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