Dr Rosa Sancho from Alzheimer's Research UK said: "We know that diseases like Alzheimer's begin in the brain decades before symptoms like memory loss start".
For their study, researchers used OCTA to compare the retinas of 39 Alzheimer's patients with 37 people with mild cognitive impairment, and 133 cognitively healthy people. The differences in density were statistically significant after researchers controlled for factors like age, gender, and level of education.
They found the blood vessel network was less dense in the Alzheimer's patients compared with the other groups.
Potentially the test could spot warning signs of Alzheimer's before vascular abnormalities show up on brain scans, which can only highlight larger blood vessels, she added. Since the retina is considered an "extension" of the brain because it sends signals to the optic nerve to create visual images, they wanted to see if similar blood vessel changes would occur in the eye.
The findings are published in the journal Ophthalmology Regina.
The imaging technique, known as optical coherence tomography angiography (Octa), allows doctors to see retinal blood vessels smaller than the width of a human hair.
In terms of how the test works, IBM's Ben Goudey says that the team uses machine learning in order to identify a specific biological marker for Alzheimer's called amyloid-beta. By the time these changes are noticed, the disease is advanced.
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Diagnosing Alzheimer's is a challenge.
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.
He also claimed that the learning model could drastically slow down the progression of Alzheimer's disease. Earlier diagnosis would also give patients and their families time to plan for the future.
"Early diagnosis of Alzheimer's disease is a huge unmet need", Dr. Fekrat said.
"The retina has a dense spider web of blood vessels, and we were interested in the density of these blood vessels". OCTA machines use light waves that reveal blood flow in every layer of the retina.
Upwards of 5.5 million Americans are estimated to possibly have the brain wasting disease, according to NIH, and these numbers will continue to increase in years to come if no cure is found, projections suggest an impending and staggering global impact of dementia and neurodegenerative diseases.