Description
Glaucoma is primarily an ocular disorder, yet damage to the optic nerve causes widespread structural and functional alterations in the visual brain. Prior fMRI work suggests that the visual cortex maintains its coarse-scale retinotopic organization in glaucoma, but shows a significant reduction in BOLD amplitude—an alteration that persists beyond predictions based on perimetry. However, BOLD amplitude reductions alone do not directly quantify how visual processing and function are altered. Here, we address this gap by using fMRI to measure contrast sensitivity in the cortex (the neural contrast sensitivity function - nCSF) in glaucoma patients. We first demonstrate that the nCSF approach accurately predicts visual cortex responses to stimuli varying in spatial frequency and contrast in patients and controls. In five glaucoma patients and six healthy controls we found that patients displayed reduced contrast sensitivity as compared to healthy controls in both neural (nCSF) and behavioral (bCSF) measures, with consistent relationships observed between the two estimates. Notably, these differences were observed in the projection zone of the central visual field (0–5° eccentricity) of patients with early stage glaucoma, a region often considered largely spared by conventional standard automated perimetry. These findings provide preliminary evidence that behavioral contrast sensitivity deficits in glaucoma are reflected in the cortex. This highlights the potential of the nCSF as a tool for quantifying and understanding vision loss allowing the characterization of glaucoma’s impact along the visual pathway beyond the eye.
Lay Abstract
Glaucoma is a common eye disease that damages the optic nerve, causing vision loss. While it begins in the eye, this damage also affects how the brain processes visual information. Standard clinical tests, which map where vision has been lost across the visual field, may not capture the full picture of this impact.
In this study, we used brain imaging (fMRI) to measure contrast sensitivity (how easy it is to see faded vs bold images) directly in the visual cortex. We compared five glaucoma patients with six healthy volunteers and found that patients showed reduced contrast sensitivity in both brain responses and standard behavioural vision tests, with the two measures aligned.
Importantly, these differences were detected in the brain region responsible for central vision, even in these patients with early-stage glaucoma. This is a region that standard eye tests often suggest is relatively unaffected.
These findings indicate that brain imaging can reveal vision deficits in glaucoma that routine clinical tests may miss, and that glaucoma's effects extend into the brain itself. This approach could offer a valuable new tool for understanding vision loss in glaucoma patients.
| Lay Title | Using Brain Imaging to Measure Vision Loss in Glaucoma |
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| Role | Postdoctoral Researcher |