(RxWiki News) Glaucoma, a leading cause of blindness in the U.S., may not start in the optic nerve of the eye as previously believed. Researchers indicate the first sign of the disease may appear in the brain.
Glaucoma, an eye disease in which pressure from ocular fluid build-up damages the optic nerve, causing blindness if not detected and treated early. Damage initially affects peripheral vision, occurring gradually, making degeneration in the disease hard to detect.
But recent research from the Vanderbilt Eye Institute indicates glaucoma, rather than behaving strictly as an eye disease, acts very much like other central nervous system diseases, creating "a paradigm shift on how we think about this disease," said David Calkins, Ph.D., director of Research and associate professor of Ophthalmology at VEI.
The research lends insight into where neuronal injury first occurs in the disease and how the loss of sensory function occurs in normal aging (glaucoma risk increases with age).
In other ager-related diseases such as Alzheimer's disease and Parkinson's disease, the injury to neurons occurs very early in the distal projections in a process called dying back in which the neuronal axon loses its ability to communicate with its target, according to Calkins.
In glaucoma, researchers found that the optic-nerve axons lose their ability to communicate with their projection site in the mid-brain. They also found in mice models that the connectivity between the optic nerve and the brain dies first, before optic nerve damage is present.
Calkins said glaucoma works backward from traditional understanding of the disease. The disease, he said, "starts in the brain and works its way back to the retina" so that in the last stages of the disease, the structures nearest the eye are the last to malfunction.
The finding could lead to better diagnostic tools and earlier treatment techniques.
"This study confirms our understanding that they optic nerve is really an extension of the brain itself and perhaps our traditional view of glaucoma as an eye disease needs to be reexamined," said Dr. Christopher Quinn on behalf of DailyRx.
More than 2 million Americans have the most common form of glaucoma, and of these, as many as 120,000 are blind. A projected 3.4 million of Americans could have the disease by 2020, according to the American Health Assistance Foundation.