Researchers at Cedars-Sinai have made an important discovery that could help doctors detect Alzheimer’s disease earlier and more easily—by studying the eyes. The team closely examined changes in the retina, the light-sensitive layer at the back of the eye, to see how they relate to changes in the brain and memory.
Alzheimer’s disease is a serious condition that slowly damages memory and thinking skills. There is currently no single test that can clearly diagnose the disease, especially in its early stages. This makes it difficult to start treatment early, when it may be most helpful.
The retina is part of the central nervous system and is actually an extension of the brain. Because it is easy to see with imaging tools and doesn’t require invasive tests, the retina offers a special window into what might be going on inside the brain.
In this study, the researchers looked at retina and brain tissue samples from 86 people who had donated their bodies to science.
These samples were collected over 14 years. Some donors had normal memory and thinking, some had mild memory problems, and others had more advanced Alzheimer’s disease. The goal was to understand how changes in the eye mirror those in the brain.
What they found was striking. In the retinas of people with Alzheimer’s or even mild memory problems, there were clear signs of damage and disease. One major finding was a buildup of a protein called amyloid beta 42.
This protein is known to be toxic in large amounts and is often found in the brains of Alzheimer’s patients. The researchers found these proteins building up in specific types of eye cells called ganglion cells.
They also noticed that the body’s immune cells in the retina, called microglia, were not doing their job properly. These cells normally help clear away harmful substances like amyloid beta, but in Alzheimer’s patients, up to 80% fewer of these microglia were working effectively.
In addition, other cells involved in inflammation, such as astrocytes and more microglia, were seen gathering around the protein clumps, causing further damage.
The team also studied molecules and pathways involved in inflammation and cell death. These harmful processes were linked to areas of the brain responsible for memory, time perception, and navigation—areas that are heavily affected by Alzheimer’s.
One of the most surprising findings was that some of these damaging changes were present even in people who showed little to no memory problems during their lives. This suggests that changes in the retina might be one of the earliest signs of the disease, long before symptoms appear.
The researchers believe that one day, eye exams could be used to help detect Alzheimer’s early. This could lead to better, earlier treatment and more chances to slow the disease down before it gets worse.
This study was led by Yosef Koronyo and published in the journal Acta Neuropathologica. It adds to growing evidence that the eyes may offer a non-invasive, affordable, and accurate way to monitor brain health and track the early stages of Alzheimer’s disease.
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