The loss of blood vessels in the retina could signal Alzheimer’s disease, a new study suggests. That means a quick eye exam might flag the disease before symptoms appear.
In people with healthy brains, microscopic blood vessels form a dense web at the back of the eye inside the retina, as seen in 133 participants in a control group.
In the eyes of 39 people with Alzheimer’s disease, however, that web was less dense and even sparse in places. The differences in density were statistically significant after researchers controlled for factors including age, sex, and level of education, says Sharon Fekrat, an ophthalmologist and retinal surgeon at Duke University and senior author of the study, which appears in the journal Ophthalmology Retina.
“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,” she says.
“It’s possible that these changes in blood vessel density in the retina could mirror what’s going on in the tiny blood vessels in the brain, perhaps before we are able to detect any changes in cognition.”
The study found differences in the retinas of people with Alzheimer’s disease when compared to healthy people and to those with mild cognitive impairment, often a precursor to Alzheimer’s disease.
With nearly 6 million Americans living with Alzheimer’s disease and no viable treatments or noninvasive tools for early diagnosis, its burden on families and the economy is heavy. Scientists have also studied other changes in the retina that could signal trouble upstream in the brain, such as thinning of some of the retinal nerve layers.
“We know that there are changes that occur in the brain in the small blood vessels in people with Alzheimer’s disease, and because the retina is an extension of the brain, we wanted to investigate whether these changes could be detected in the retina using a new technology that is less invasive and easy to obtain,” says Dilraj S. Grewal, an ophthalmologist and retinal surgeon and a lead author of the study.
Researchers used a noninvasive technology called optical coherence tomography angiography (OCTA). OCTA machines use light waves that reveal blood flow in every layer of the retina.
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. Such techniques to study the brain are invasive and costly.
“Ultimately, the goal would be to use this technology to detect Alzheimer’s early, before symptoms of memory loss are evident, and be able to monitor these changes over time in participants of clinical trials studying new Alzheimer’s treatments,” Fekrat says.
The National Institutes of Health, the 2018 Unrestricted Grant from Research to Prevent Blindness, and the Karen L. Wrenn Alzheimer’s Disease Award funded the study.
Source: Duke University