A study published in February by the journal Acta Neuropathological said early signs of Alzheimer’s could show in your retinas.

According to the study, researchers wanted to understand the pathological features of Alzheimer’s in the retina. Data was collected over the course of 14 years, studying brain and retina tissues from 86 volunteers, all of whom were experiencing a decline in mental function.

Dr. Richard Isaacson, an Alzheimer’s preventive neurologist at the Institute for Neurodegenerative Diseases, told CNN, “Alzheimer’s disease begins in the brain decades before the first symptoms of memory loss.”

“You can see directly into the nervous system by looking into the back of the eye, toward the optic nerve and retina,” ophthalmologist Dr. Christine Greer told CBS News.

For the study, samples of donors were compared at three stages of cognitive function — normal functioning capacity, “mild cognitive impairment at the earliest stages of Alzheimer’s disease and those with later-stage Alzheimer’s disease dementia,” a statement released by Cedar-Sinai said.

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Those changes made in the retina were associated with changes in the entorhinal and temporal cortices, parts of the brain dealing with memory, navigation and the perception of time, per CNN.

“Microglial cells declined 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.”

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Senior author of the study Maya Koronyo-Hamaoui told Cedar-Sinai, “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.”

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She said the findings from this study could lead to developing imaging techniques that allow early diagnosis — and better monitoring — of the disease by examining the eye.

Isaacson said, “If doctors are able to identify the disease in its earliest stages, people could then make healthy lifestyle choices and control their ‘modifiable risk factors, like high blood pressure, high cholesterol and diabetes,’” according to CNN.