Eye scan detects early Alzheimer's
Researchers have found that eye scans can detect signs of Alzheimer’s disease within seconds.
Two studies have shown that the small blood vessels in the retina at the back of the eye are altered in patients with Alzheimer’s. Even patients who have a family history of Alzheimer’s but have no symptoms show these telltale signs. Researchers can even distinguish between people with Alzheimer’s and those with only mild cognitive impairment.
A new kind of precise and non-invasive imaging called optical coherence tomography angiography (OCTA) has assisted much of the recent research on the eye’s connection with Alzheimer’s. It enables physicians to see the smallest veins in the back of the eye, including the red blood cells moving through the retina.
Because the retina is connected to the brain by way of the optic nerve, researchers believe that the deterioration in the retina and its blood vessels may mirror the changes going on in the blood vessels and structures in the brain, thereby offering a window into the disease process.
Diagnosing Alzheimer’s is a currently a challenge. Some techniques can detect signs of the disease but are impractical for screening millions of people: brain scans are expensive and spinal taps can be harmful. Instead, the disease is often diagnosed through memory tests or observing behaviour changes. By the time these changes are noticed, the disease is advanced. Even though there is no cure, early diagnosis is critical as future treatments are likely to be most effective when given early. Early diagnosis would also give patients and their families time to plan for the future.
The goal of this latest research is to find a quick, inexpensive way to detect Alzheimer’s at the earliest signs.
Researchers at Duke University used OCTA to compare the retinas of Alzheimer’s patients with those of people with mild cognitive impairment, as well as healthy people. They found that the Alzheimer’s group had loss of small retinal blood vessels at the back of the eye and that a specific layer of the retina was thinner. Even people with mild cognitive impairment did not show these changes.
Because genes play a significant role in how Alzheimer’s disease begins and progresses, another team of researchers from Sheba Medical Center in Israel examined 400 people who had a family history of the disease but showed no symptoms themselves. They compared their retina and brain scans with those who have no family history of Alzheimer’s.
They found that the inner layer of the retina is thinner in people with a family history. The brain scan showed that their hippocampus, an area of the brain that’s first affected by the disease, had already begun to shrink. Both factors, a thinner inner retina layer and smaller hippocampus, were associated with scoring worse on a cognitive function test.
“A brain scan can detect Alzheimer’s when the disease is well beyond a treatable phase,” said lead researcher Dr Ygal Rotenstreich, ophthalmologist at the Goldschleger Eye Institute at Sheba Medical Center. “We need treatment intervention sooner. These patients are at such high risk.”
Results from these studies were presented at the 2018 Annual Meeting of the American Academy of Ophthalmology.
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