Eye Exam Could One Day Detect Early Alzheimer's Disease

by Liz Neporent
March 27, 2023 at 10:05 AM UTC

Alzheimer's shows up in the retinas.

Clinical Relevance: An eye exam may someday detect Alzheimer’s disease, even in the early stages

  • Researchers found increased amyloid beta protein and other biomarkers in the retinas of patients with Alzheimer’s disease or mild cognitive impairment.
  • The changes in the retina were unevenly distributed and correlated with changes in the parts of the brain responsible for memory, navigation, and the perception of time.
  • Retinal biomarkers could be used to predict future cognitive decline and track its progress through noninvasive screening.

Researchers have made a major breakthrough in the early detection of Alzheimer’s disease (AD) by analyzing protein variations in the eyes. 

In one of the largest and most comprehensive studies of its kind, a team led by scientists from Cedars-Sinai Medical Center in Los Angeles collected retinal and brain samples from 86 donors over a 14-year period. By comparing tissues from subjects with Alzheimer’s disease or mild cognitive impairment (MCI) to those from donors with normal cognition, the researchers were able to identify key biomarkers that may indicate the onset of AD.

One of the most significant findings showed an increased buildup of amyloid beta protein in the ganglion cells of the retinas in the patients with AD and MCI. This protein can form clumps and plaques that disrupt the normal functioning of brain cells. Researchers said these changes correlated with changes in the parts of the brain responsible for memory, navigation, and the perception of time.

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Patients with AD and MCI had higher numbers of astrocytes and microglia, immune cells that surround the amyloid beta plaques. They also observed that up to 80 percent fewer microglial cells were clearing amyloid beta proteins from the retina and brain. This, they speculated, was an indication that the immune system was not functioning properly in these patients. And additionally, they observed abnormal protein clusters within the retinas of AD and MCI subjects, including small clusters of amyloid beta protein that can be toxic to brain cells.

Different parts of the retina showed uneven distribution of all these developments. The inner layers and peripheral subregions exhibited the most pronounced accumulations of amyloid beta protein and other biomarkers in the dementia patients. Retinal variances accurately correlated with the pathological stage of Alzheimer’s disease and patients’ cognitive status, suggesting that they could be a possible early predictor of future cognitive decline.

According to Maya Koronyo-Hamaoui, professor of Neurosurgery, Neurology, and Biomedical Sciences at Cedars-Sinai and senior author of the study, this research is an important step toward understanding the complex effects of Alzheimer’s disease on the retina. 

“Our study is the first to provide in-depth analyses of the protein profiles and the molecular, cellular, and structural effects of Alzheimer’s disease in the human retina and how they correspond with changes in the brain and cognitive function,” Koronyo-Hamaoui said in a statement.

Doctors may be able to use this information to track the risk and progression of Alzheimer’s disease. With further research, scientists could develop an eye exam to analyze the retina and detect early Alzheimer’s, the researchers said.

“These findings may eventually lead to the development of imaging techniques that allow us to diagnose Alzheimer’s disease earlier and more accurately and monitor its progression noninvasively by looking through the eye,” Koronyo-Hamaoui said.

The open access investigation was published last month in the journal Acta Neuropathologica.

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