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An Eye Test Aids Early Diagnosis of Alzheimer's Disease

Noninvasive retinal scan shows signs of early stages

En español | A noninvasive scan that measures the width of blood vessels in the back of the eye shows promise as a way to help diagnose Alzheimer's disease in its early stages, an Australian researcher reports.

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Shaun Frost, a scientist at the Australian e-Health Research Center, found that blood vessel changes in the light-sensitive tissue of the retina reflect an accumulation of amyloid plaque in the brain, thought to be an early sign of Alzheimer's.

New study explores retina characteristics as possible biomarkers for Alzheimer’s disease

Photo by: Jacques M. Chenet/Corbis

Noninvasive retinal scan could show early stages of Alzheimer's disease.

"We're seeing signs of the plaque burden increasing in the brain a long time before we see the cognitive deficits of Alzheimer's disease," Frost said during a presentation at the 2011 Alzheimer's Association International Conference in Paris last month.

Frost measured the size of the retinal arteries and veins, then calculated a ratio between the two. He found that in people with Alzheimer's disease, the veins get smaller and the arteries appear to get bigger, proportionately.

"The artery-to-vein ratio in the retina was higher in Alzheimer's disease," Frost told the conference. And, he said, "if we look specifically at just the veins, we see a thinning of those in Alzheimer's disease."

Frost scanned the eyes of 13 older people diagnosed with Alzheimer's and 13 with mild cognitive impairment, comparing them with healthy people. "It's not likely this test would be a stand-alone, definitive test for Alzheimer's disease," he said. But, he added, it could be used in conjunction with other new, very expensive screening tests.

William Klunk, M.D., an Alzheimer's expert at the University of Pittsburgh, agreed, saying in a discussion at the conference that current tests — special scans and spinal taps used to detect Alzheimer's-related changes in the brain — are a bit too invasive and expensive for widespread use as screening tools. He pointed out, however, that Frost's test uses equipment you'd find in any optometrist's office, simply measuring the width of the blood vessels.

Klunk, who was not associated with Frost's study, said this simpler test could be used to help identify people who are candidates to undergo one of the more invasive, expensive tests. He also described Frost's work as a "very important piece of a several-piece puzzle."

Frost's work builds on recent research by teams from Harvard Medical School, Cedars-Sinai Medical Center, Israel's Weizmann Institute of Science and the University of Western Australia that linked retinal abnormalities to early-stage Alzheimer's disease.

"The retina is very, very closely related to the brain," Frost explained at the conference. "The tissues that we find are very representative of the tissues of the brain."

Michael Haederle is a freelance writer whose work has appeared in People, The New York Times and the Los Angeles Times.

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