San Antonio (Feb. 17, 2004) – A research group at The University of Texas Health Science Center at San Antonio is examining the intriguing possibility of a link between glaucoma and Alzheimer’s disease. The group is working with rat and mouse models of glaucoma to seek a possible connection. Glaucoma is a blinding disease that is difficult to detect until substantial vision loss has occurred.
Alzheimer’s includes an increased incidence of cerebral vascular disease and hemorrhagic stroke marked by abnormal deposits of a toxic protein called amyloid in blood vessel walls, said Stuart McKinnon, M.D., Ph.D., department of ophthalmology. “There is debate about what causes the process. We have found that amyloid also is deposited in the eyes, optic nerves and brains of rats in an experimental animal model of glaucoma.”
Other groups have shown that patients with Alzheimer’s have higher incidence of glaucoma (as much as five times higher) and progression of their glaucoma is faster. “Glaucoma is a neurodegenerative disease, so why should its mechanism be different from other neurodegenerative diseases?” Dr. McKinnon said. “We’ve been finding that glaucoma seems to share similarities with Alzheimer’s.”
Dr. McKinnon’s lab is looking at the eyes and brains of rats and transgenic mice that produce proteins known to be mutated in the inherited forms of Alzheimer’s. The group recently developed a mouse glaucoma model, one of the first for glaucoma, to examine mice that over- or under-express proteins involved in Alzheimer’s. The researchers are checking to see whether these mice are overly susceptible to glaucoma damage.
If a connection is found, it is possible that treatments for Alzheimer’s could be used to treat glaucoma and vice versa. It’s also possible that physicians one day might be able to diagnose Alzheimer’s disease early by looking at the eye.
There is a push to diagnose Alzheimer’s before patients lose their cognitive abilities. Scientists are working on ways to image the amyloid plaques. “In the animal models we use, amyloid shows up early, so we hope we can take advantage of that and develop a test to diagnose glaucoma in humans earlier, before vision loss occurs,” Dr. McKinnon said. Small animal imaging devices at the Health Science Center will be used, he said.
The McKinnon group also is one of the first to explore gene therapy as a potential treatment for glaucoma. The inserted gene modulated the process of programmed cell death in ganglion cells, the retinal cell type damaged in glaucoma.