However, new research may have found the next breakthrough in pinpointing early signs of the disease, no pain or inconvenience required. But because the retina is an extension of the brain, they have been keen on investigating whether these changes could be detected in the retina using new technology that is less invasive and easy to obtain.
Dr Sharon Fekrat, from Duke University Medical Centre in the United States, said: "We're measuring blood vessels that can't be seen during a regular eye exam and we're doing that with relatively new noninvasive technology that takes high-resolution images of very small blood vessels within the retina in just a few minutes". Not only were the researchers able to detect differences between the Alzheimer's patients and the other two groups, but they were also able to see differences among the Alzheimer's patients that appeared to be linked with the severity of the disease.
She and her team found microscopic blood vessels formed in a dense web at the back of the eye, inside the retina, in 133 of the study's healthy participants.
The eye scan used in the study could reveal changes in tiny capillaries, most less than half the width of a human hair, before blood vessel changes show up on a brain scan, according to the study. In addition, a specific layer of the retina was thinner in those with Alzheimer's. For those with Alzheimer's, the same vessels are sparse and lacking in different areas. Their study was published online today in Ophthalmology Retina, a journal of the American Academy of Ophthalmology.
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The eye scan is called optical coherence tomographic angiography, or OCTA for short. "It's not possible for current techniques like a brain scan or lumbar puncture (spinal tap) to screen the number of patients with this disease".
"Cognitively normal, healthy individuals do not have these changes in their retina", said Dr. Sharon Fekrat, the study's lead researcher Dr. Sharon Fekrat. Our work is not done.
With almost a large portion of the world living with Alzheimer's disease and no viable treatments or non-invasive tools for early diagnosis, the burden on the families and the economy becomes heavy. "If we can detect these blood vessel changes in the retina before any changes in cognition, that would be a game changer".
Researchers believe the goal would be to use this technology to detect Alzheimer's in the early stages before symptoms of memory loss become apparent.