Occipital pole surface area reduction found in patients with glaucoma
Patients with glaucoma showed significant reduction in the occipital pole surface area in the left and right hemispheres, according to a cross-sectional study published in the Journal of Glaucoma.
“This study has shown that the surface areas of right and left occipital poles measured using 3T MRI is correlated with structural and functional parameters of glaucoma,” Carolina P. Gracitelli, MD, PhD, of the department of ophthalmology and visual sciences at Paulista School of Medicine in São Paulo Hospital at Federal University of São Paulo, and colleagues wrote.
Ninety-six eyes of 48 patients (30 with glaucoma, 18 healthy) from the Glaucoma Unit of the Federal University of São Paulo were included in the study. Each patient underwent a comprehensive ophthalmologic examination and was categorized as control if he or she had normal results on the examination.
All participants underwent standard automated perimetry (SAP), spectral domain OCT and 3.0-Tesla MRI.
Results showed that patients with glaucoma had significantly lower SAP mean deviation values, retinal nerve fiber layer (RNFL) thicknesses, IOP and cup-to-disc ratios compared with the control group.
Investigators observed differences between the occipital pole surface area in the left hemisphere in patients with glaucoma and the control participants (P = .043). They saw a similar difference in occipital pole surface area of the right hemisphere between patients with glaucoma and the control group (P = .029). The results also revealed a difference in the left (P = .003) and right (P < .032) occipital pole surface areas between mild glaucoma and moderate to severe glaucoma.
The occipital pole surface area in the left and right hemispheres correlated with SAP 24-2 mean deviation values (P =.001 and P < .001), RNFL thickness(P = .006 and P = .007), visual acuity (P < .001 and P < .001) and age (P = .01 and P = .046).
“There is a correlation between the occipital pole surface areas of both hemispheres and functional and structural ocular parameters in glaucoma patients, even after adjusting for age,” Gracitelli wrote. “These findings corroborate previous findings, which indicate that damage caused by glaucoma involves not only ocular structures, but the entire visual pathway.” – by Erin T. Welsh
Disclosures: The authors report no relevant financial disclosures.
Perspective
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While the exact pathophysiology of glaucoma remains a mystery, recent studies suggest a neurodegenerative process that extends to the brain. This enigmatic disease does not limit itself to ocular damage but affects the entire visual pathway. Gracitelli and colleagues contributed further and found that cortical brain changes are correlated with functional and structural ocular parameters. Is it time to add MRI to our glaucoma work-ups?
Ordering an MRI is certainly not justified or cost effective for glaucoma diagnosis and management, but further research may determine other markers that can be used for a fraction of the cost.
Neuroprotective drugs could be an important way to preserve the optic nerve and brain function. When do cortical changes occur? While brain damage seems to occur early in the disease, future studies will attempt to understand the exact relationship. Is there atrophy in an area that is no longer needed due to decreased ocular function? Is it a simultaneous neurodegeneration across the visual pathway or does brain damage actually precede optic nerve damage? If it is the latter, it may be useful to selectively employ MRIs in those hard-to-diagnose cases. Time, and more studies, will tell.
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