KINGSTON, R.I. (CBS) – Researchers in New England are developing a screening process that could help detect Alzheimer’s disease decades before any symptoms appear. The University of Rhode Island and Butler Hospital in Providence have announced a five-year clinical trial to develop a low-cost and less-invasive retinal scan.

They hope the scan will allow doctors to identify the signs of Alzheimer’s 20 years or more before symptoms develop. Microscopic changes in the retina could indicate that changes are also taking place in the brain that put someone at high risk for the disease.

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Right now, researchers say, a single Alzheimer’s test costs up to $4,500 and often isn’t done until symptoms start appearing and it’s too late for treatments that could have helped.

“We believe this could significantly lower the cost of testing,” URI vice president for research Peter Snyder said in a statement. “We may then identify more people in the very earliest stage of the disease, and our drug therapies are likely to be more effective at that point and before decades of slow disease progression.”

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The study is seeking 300 volunteers between the ages of 55 and 80. Learn more about volunteering here.