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 when compared to people with mild cognitive impairment and healthy people.
The research was supported by National Institutes of Health (P30EY005722), the 2018 Unrestricted Grant from Research to Prevent Blindness, and the Karen L. Wrenn Alzheimer's Disease Award.
The test, which examines microscopic blood vessels at the back of the eye, has the potential to spot the disease decades before clinical symptoms appear, experts said after new trials showed promising results. This latest research is the largest study to date and adds to the current literature as scientists strive to find a quick, noninvasive, and low-priced way to detect Alzheimer's at the earliest stages. The differences in density were statistically significant after researchers controlled for factors including age, sex, and level of education, said Duke ophthalmologist and retinal surgeon Sharon Fekrat, M.D., the study's senior author.
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.
An OCTA scan could even 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 such as an MRI or cerebral angiogram, which highlight only larger blood vessels.
The study found differences in the retinas of those with Alzheimer's disease when compared to healthy people and to those with mild cognitive impairment, often a precursor to Alzheimer's disease.
The typical process for diagnosing Alzheimer's isn't a fun one. Some techniques can detect signs of the disease but are impractical for screening millions of people: Brain scans are expensive and spinal taps have risks.
"Early diagnosis of Alzheimer's disease is a huge unmet need", Dr. Fekrat said. If we can detect these blood vessel changes in the retina before any changes in cognition, that would be a game changer'.
Now the only ways to definitively diagnose Alzheimer's are through expensive brain scans or by taking a fluid sample from the patient's spinal cord. Our work is not done.