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A study of more than 200 people at the Duke Eye Center in the USA suggests the loss of blood vessels in the retina could signal Alzheimer’s disease through a quick eye examination.

The research looked at the blood vessels within people’s retinas, comparing the retinas of people with healthy brains to those with Alzheimer’s.

In the 133 participants with healthy brains, the study found that the blood vessels formed a dense web at the back of their eyes inside the retina. However, in the eyes of 39 people with Alzheimer’s disease, the study discovered that the web was less dense and sparse in places.

Duke Eye Center Ophthalmologist and Retinal Surgeon, and the study’s senior author, Sharon Fekrat, M.D., found that the differences in web density were significant.

She explained: “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.

“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.”

Additionally, scientists at the Center 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,” said Dilraj S. Grewal, M.D., a Duke ophthalmologist and retinal surgeon and a lead author on the study.

The Duke study 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.

According to the centre, an OCTA scan could reveal changes in tiny capillaries before blood vessel changes show up on a brain scan such as an MRI, which highlight only larger blood vessels. However, these 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,” Sharon commented.

The research was supported by National Institutes of Health, the 2018 Unrestricted Grant from Research to Prevent Blindness, and the Karen L. Wrenn Alzheimer’s Disease Award.

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