Cases of Alzheimer’s are estimated to reach 78 million by 2030. With a non-existent cure, researchers are working to prevent the development, and progression, of the neurodegenerative condition. Early diagnosis does save lives, and an early Alzheimer’s diagnosis can be beneficial, especially in regard to management and treatment.
There are currently many ways to test and diagnose Alzheimer’s, such as MRI brain imaging and postmortem tests. Yet, a new study suggests that if we want to look out for Alzheimer’s, we need to start looking at our eyes.
What Do Our Eyes Say About Our Brains?
Your eyes consist of the lens, the pupil, the optic nerve, and the retina. The retina can be found at the back of the eye. It is part of the nervous system and is connected to the brain via the optic nerve. According to the National Eye Institute, much of the information known about the brain comes from studying the eye. This is because the retina is far more accessible for investigation.
“The ability to easily detect the biological hallmarks of Alzheimer’s in the eye is intriguing, in that it may provide the ability to detect the disease in a noninvasive manner, in earlier stages before symptoms appear,” says Percy Griffin, Ph.D., director of scientific engagement at the Alzheimer’s Association, to Everyday Health.
Eye Exams for Alzheimer’s
A study, led by Cedars-Sinai investigators, examined how changes in the retina may correspond to cognitive changes in the brain.
The researchers examined donated tissue from the retina and brains of 86 people who had different degrees of mental decline.
According to the researchers, this factor made the study the largest one on retinal samples and dementia conducted so far. The retina tissue was then compared to tissue from donors who had a normal cognitive function.
Eye changes may indicate Alzheimer’s disease
Per the findings, published in Acta Neuropathologica, changes in the retina correlated with changes in areas of the brain. These areas were responsible for cognitive functionalities, like memory, navigation, and the perception of time.
The researchers also discovered excess amounts of the protein beta-amyloid 42 in the retinas of people with mild cognitive impairment and Alzheimer’s disease. According to the National Institute on Aging, high levels of beta-amyloid 42 clump together to form a protein that collects between neurons and disrupts cell function.
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For those with mild cognitive impairment and Alzheimer’s disease, the researchers also found an accumulation of beta-amyloid protein in the ganglion cells of their retinas. Ganglion cells play a role in the receiving and transportation of virtual information.
Aside from the acclimation of beta-amyloid proteins, the researchers also noted that levels of microglial cells declined by 80% in people with cognitive issues. Microglial cells work like immune cells, managing other cells and eliminating beta-amyloid from the brain and retina.
“These findings may lead to the development of imaging techniques that would be able to diagnose Alzheimer’s disease earlier and more accurately,” says Maya Koronyo-Hamaoui, Ph.D., and senior author.
Koronyo, who is also a professor of neurosurgery, neurology, and biomedical sciences at Cedars-Sinai in Los Angeles, added that changes in the retina were also detected in patients who didn’t appear to have any cognitive issues. This suggests that the state of the retina may become a possible early predictor of later cognitive issues.
Why does Alzheimer’s disease appear in the eyes?
Most diseases that affect the brain will impact eye health.
According to Amit Sachdev, M.D., M.S., a medical director in the Department of Neurology at Michigan State University, the brain and the eye have nerves running between them. These nerves contain a body and axon,
“The body contains all-important parts to regulate the nerves maintenance and growth [and] the axon is like a very long tail.” explained Dr. Sachdev to Prevention. Dr. Sachdev added that if the axon is damaged, then it will begin to degenerate.
“When you look at the eyes, you are looking at the tips of nerves,” he says. “The nerve runs all the way to the back of the brain. As you can imagine, brain disease might easily interfere with the health of these very long projections.”
Will eye tests look for Alzheimer’s?
Maybe, but not anytime soon.
For one, the study was conducted on postmortem tissue, so it will take some time before researchers can draw the same conclusions when examining a live human being. That said, the study’s findings do reinforce that the eyes are the windows to the soul, and they can tell us more about ourselves than we think.
Want to know more?
If there’s one thing that we’re worried about losing as we age, it’s definitely our vision. If you’re hoping to maintain 20/20 vision over the next 20 years and beyond, here’s a guide to protecting eye health and longevity as you age.
MAIN IMAGE CREDIT: Photo by Kindel Media
References
Koronyo, Y., Rentsendorj, A., Mirzaei, N. et al. (2023). Retinal pathological features and proteome signatures of Alzheimer’s disease. Acta Neuropathol 145, 409–438. https://doi.org/10.1007/s00401-023-02548-2
