A team of researchers in the U.S. believe that a simple eye exam may be able to screen patients for Alzheimer’s disease long before they exhibit symptoms or signs of dementia.
“The eye can really serve as a model for studying neurodegenerative diseases,” Dr. Gregory Van Stavern, professor of ophthalmology and visual sciences at Washington University in St. Louis, told CTV News. “And we can access the eye a lot easier than we can access the brain.”
Scientists know that Alzheimer’s and dementia can begin to take root in the brain up to two decades before symptoms such as memory loss or mood changes become obvious. And while simple tests currently exist for the early discovery of diseases such as colon cancer and diabetes, there is nothing comparable when it comes to Alzheimer’s. Today, only tests such as spinal taps or PET scans can detect Alzheimer’s in its earliest stages.
“You can imagine those are invasive tests,” Van Stavern said. “They’re expensive and very difficult to apply to the general population.”
In a new study, Van Stavern and a team of researchers used a relatively simple exam to study the eyes of 30 seniors. Although none of their subjects exhibited symptoms of Alzheimer’s, PET scans and/or spinal taps had previously revealed that 17 of them were at risk of developing the disease in the future due to elevated levels of brain plaque.
Through the eye exams, which use a technology similar to what is already found in many eye doctors’ offices, the researchers discovered that those 17 had thinner retinas -- the part of the eye that converts images into signals for the brain -- as well as fewer blood vessels in their retinas than the other research subjects, signalling less blood flow in the eyes and brain.
Dr. Rajendra S. Apte, who also teaches ophthalmology and visual sciences at Washington University, co-authored the study.
“What we wanted to examine was whether we could use the eye as a window to the brain,” he told CTV News.
“The finding that there were abnormalities in the blood vessels in the eye so early in disease was very surprising,” he added. “So this tells us that there are things going on very early in disease that we should be looking for even in the brain.”
Although more research needs to be done to definitively prove a link between the state of one’s retinas and Alzheimer’s, if verified it could mean that the disease can be detected earlier and easier, thus improving treatment and patient outcomes.
“Since these pathologic changes in Alzheimer’s disease begin about 20 years before dementia develops, it means practically by the time someone develops dementia there is so much loss of neural tissue that the medications, the treatments are not very effective,” Van Stavern explained. “There’s a push now to start intervening early in the preclinical stage with medications… So the idea would be using a test like this, which is non-invasive, as a way of screening people who might be at risk for Alzheimer’s disease.”
Meanwhile in Canada, a Montreal-based company called Optina Diagnostics believes they have developed another test for detecting Alzheimer’s via a relatively simple, but somewhat different, type of retinal examination. The company, which is currently conducting clinical trials in collaboration with McGill University in Montreal and Sunnybrook Hospital in Toronto, is hoping to receive regulatory approval for its test in 2019.
The development of such quick, inexpensive and non-invasive eye tests are welcome news to Alzheimer Society of Canada CEO Pauline Tardif.
“Any disease modifying therapies that might be developed in the future will be most effective at the very, very early stages of the disease,” she told CTV News. “And if we can have… diagnostic tools such as this through the retina, that’s really exciting.”
CTV Medical News 8/29/18