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Eyes are more than a window to the soul — they’re also a reflection of a person’s cognitive health.
“The eye is the window to the brain,” says ophthalmologist Dr. Christine Greer, director of medical education at the Institute for Neurodegenerative Diseases in Boca Raton, Florida. “You can see directly into the nervous system by looking at the back of the eye, toward the optic nerve and retina.”
Research has explored how the eye can help diagnose Alzheimer’s disease before symptoms begin. The disease is well advanced by the time memory and behavior are affected.
“Alzheimer’s disease begins in the brain decades before the first symptoms of memory loss,” said Dr. Richard Isaacson, an Alzheimer’s preventive neurologist as well as the Institute for Neurodegenerative Diseases.
If doctors detect the disease in its earliest stages, people can make healthy lifestyle choices and control their “modifiable risk factors, such as high blood pressure, high cholesterol and diabetes,” says Isaacson,
How early do we see signs of cognitive decline? To find out, a recent study examined donated tissue from the retina and brain of 86 people with varying degrees of mental decline.
“Our study is the first to provide an in-depth analysis of protein profiles and the molecular, cellular, and structural effects of Alzheimer’s disease on the human retina and how this corresponds to changes in the brain and cognitive function,” said senior author Maya Koronyo-Hamaoui, a professor of neurosurgery and biomedical sciences. sciences at Cedars-Sinai in Los Angeles, in a statement.
“These changes in the retina are associated with changes in parts of the brain called the entorhinal and temporal cortices, a hub for memory, navigation and the perception of time,” said Koronyo-Hamaoui.
Study investigators collected retinal and brain tissue samples over 14 years from 86 human donors with Alzheimer’s disease and mild cognitive impairment – the largest group of retinal samples ever studied. study, according to the authors.
The researchers then compared samples from donors with normal cognitive function to those with mild cognitive impairment and to those with late-stage Alzheimer’s disease.
The studying, published in February in the journal Acta Neuropathologica, found significant increases in beta-amyloid, a key marker of Alzheimer’s disease, in people with Alzheimer’s and early cognitive decline.
Microglial cells decreased by 80% in those with cognitive issues, the study found. These cells are responsible for repairing and maintaining other cells, including clearing beta-amyloid from the brain and retina.
“Inflammatory markers were (also) found, which may be an equally important marker for disease progression,” said Isaacson, who was not involved in the study.
“The findings are also evident in people with no or minimal cognitive symptoms, suggesting that new eye tests may be well positioned to aid in early diagnosis.”
Study researchers found higher numbers of immune cells tightly surrounding amyloid beta plaques as well as other cells responsible for inflammation and cell and tissue death.
Tissue atrophy and inflammation in cells in the far periphery of the retina were most predictive of cognitive status, the study found.
“These findings may lead to the development of imaging techniques that allow us to diagnose Alzheimer’s disease earlier and more accurately,” said Isaacson, “and monitor its progression non-invasively. by looking in the eye.”