For the study, scientists used Octa to compare the retinas of 39 Alzheimer's patients, 37 people with mild cognitive impairment, and 133 healthy individuals with normally functioning brains. The differences in density were statistically significant after researchers controlled for factors including age and sex.
They found the blood vessel network was less dense in the Alzheimer's patients compared with the other groups. For those with Alzheimer's, the same vessels are sparse and lacking in different areas.
An OCTA scan could even reveal the changes in tiny capillaries nearly less than half the width of a human hair, before the blood vessels changes are displayed on a brain scan such as an MRI or cerebral angiogram, which highlights only the larger blood vessels.
The findings are published in the journal Ophthalmology Regina.
Standard optical equipment is not now strong enough to detect the vessels, which are about half the width of a strand of hair, but they did have success using a non-invasive technology called optical coherence demography and geography.
Dr. Fekrat believes that if more people in the earlier stages of Alzheimer's could be recruited into clinical trials, there is a bigger potential for better treatments to be discovered.
He also claimed that the learning model could drastically slow down the progression of Alzheimer's disease.
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. Earlier diagnosis would also give patients and their families time to plan for the future.
Dr Fekrat said: "Early diagnosis of Alzheimer's disease is a huge unmet need".
Alzheimer's disease is now diagnosed once symptoms appear, such as memory troubles and perception problems.
"It's not possible for current techniques like a brain scan or lumbar puncture to screen the number of patients with this disease".
If we can detect these blood vessel changes in the retina before any changes in cognition, that would be a game changer'.
In the USA alone, 5.8 million people are living with Alzheimer's dementia, according to 2019 data from the Alzheimer's Association.