A new study of more than 200 people at the Duke Eye suggests the loss of blood vessels in the retina could signal Alzheimer’s disease.

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. The study showed that in the eyes of 39 people with Alzheimer’s disease, that web was less dense and even sparse in places. The differences in density were statistically significant, according to senior author Sharon Fekrat, MD, Duke ophthalmologist and retinal surgeon.

“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 said. “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 those with Alzheimer’s disease when compared to healthy people and to those with mild cognitive impairment, often a precursor to Alzheimer’s disease.

Researchers have studied other changes in the retina that could signal problematic conditions 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,” said lead author Dilraj Grewal, MD, a Duke ophthalmologist and retinal surgeon. The Duke study used optical coherence tomography angiography (OCTA), a non-invasive test that uses light waves to reveal blood flow in every layer of the retina. Grewal noted that an OCTA scan 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 such as an MRI or cerebral angiogram, which highlight only larger blood vessels.

Reference:

Yoon, et al. “Retinal Microvascular and Neurodegenerative Changes in Alzheimer’s Disease and Mild Cognitive Impairment Compared with Control Participants.” Ophthalmology Retina, 2019; DOI: 10.1016/j.oret.2019.02.002

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