The decreasing number of capillaries in the posterior eye could enable a new, non-invasive way of detecting cognitive impairment. American researchers believe that these capillaries can also be used as biomarkers for Alzheimer's disease.
The researchers identified vascular changes in the human eye in a non-invasive way through infrared camera images. This was made possible with the help of the optical coherence tomography angiography (also known as OCT-A), which allows the eye posterior to be visually assessed. According to the researchers, the new technology turns the eye into an ideal mirror of what happens in the brain.
"As soon as our results are confirmed, this approach could be used as another biomarker to detect Alzheimer's risks in patients," explains Dr. Amani Fawzi. He adds: "These patients could be observed much more closely. They would also be the ideal first candidates for new therapies in the fight against Alzheimer's disease and the slowing of associated symptoms.”
Dr. Fawzi emphasized the greater effectiveness of Alzheimer's therapies when they begin before brain damage and cognitive decline takes place. It has been known for some time that patients with Alzheimer's have reduced retinal blood flow and blood vessel density. However, it has not yet been known whether these changes already exist in patients with an early form of the disease or with a slight cognitive decline.
Professor Sandra Weintraub, a study co-author, suggests using the new technique in multicenter clinical trials. More comprehensive data are important in order to validate the new marker and discover the best possible algorithms for Alzheimer's risk recognition.
32 participants with cognitive impairments took part in the study. They were compared with subjects who had normal cognitive values for their age. All participants also underwent OCT-A. The researchers investigated whether the capillaries in the posterior eye were different in the two test groups.
Dr. Fawzi concludes: "Ideally, the retinal findings match those of other biomarkers in the brain. Long-term studies are also important to determine whether the capillaries in patients with Alzheimer's dementia could change more drastically.”
Yi Stephanie Zhang, Nina Zhou, Brianna Marie Knoll, Sahej Samra, Mallory R. Ward, Sandra Weintraub, Amani A. Fawzi. Parafoveal vessel loss and correlation between peripapillary vessel density and cognitive performance in amnestic mild cognitive impairment and early Alzheimer’s Disease on optical coherence tomography angiography. PLOS ONE, 2019; 14 (4): e0214685 DOI: 10.1371/journal.pone.0214685