Your Eyes May Show Early Signs of Alzheimer’s: Study

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Recent research has found that changes in the retina and optic nerve may show the earliest signs of Alzheimer’s disease, at a time when treatments to slow the degenerative condition might be more effective.

Your Eyes Are Windows to the Brain

“There is research to suggest that the changes associated with Alzheimer’s, such as the formation of amyloid plaques, start a decade or more before the onset of symptoms like memory loss,” Dr. Theodore Strange, chair of medicine at Staten Island University Hospital, part of Northwell Health in New York, told The Epoch Times.

“This time period is often called ‘preclinical Alzheimer’s disease’ and likely begins 10 to 15 years before patients have symptoms,” he continued, noting that by the time symptoms are apparent, patients already have moderate levels of the disease—which can take four to eight years to progress to its latest stages.

To discover how early Alzheimer’s could be detected using the eyes, researchers analyzed donated tissue from the retina and brains of 86 people with different degrees of cognitive decline. They compared those samples to ones from people with normal cognitive function.

The retina is a thin layer of tissue at the back of the eye that contains cells called photoreceptors that detect light and transmit visual information to the brain. The optic nerve carries visual information from the retina to the brain.

Researchers found that the retinas of patients with mild cognitive impairment and Alzheimer’s disease had:

• An “overabundance” of amyloid beta-42-protein, which in Alzheimer’s disease patients clumps together to form plaques that disrupt brain function.
• Accumulation of amyloid beta-protein in ganglion cells, which bridge visual input from the retina to the optic nerve.
• Increased amounts of astrocytes and immune cells—microglia cells, tightly surrounding amyloid beta plaques.
• Over 80 percent fewer microglial cells clearing amyloid beta-proteins from the retina and brain.

The changes were also evident in people who appeared mentally healthy, making this a potential early predictor of cognitive decline.

These retinal changes correlated with the pathological stage of Alzheimer’s disease and patients’ mental status. They also correlated with changes in parts of the brain responsible for memory, navigation, and the perception of time.

Current Eye Tests That Help Detect Alzheimer’s

Currently, there’s no one test to determine if a patient has Alzheimer’s disease.

“The retina, a developmental extension of the brain, offers an unparalleled opportunity for affordable, noninvasive monitoring of the central nervous system,” study first author Yosef Koronyo, who holds a master’s in microbiology and biotechnology and is a research associate in the Cedars-Sinai Department of Neurosurgery, said in a statement.

There are currently eye tests that doctors can use to detect Alzheimer’s disease risk that rely on the eye’s reaction to a stimulus, or changes to its structure.

Optical Coherence Tomography (OCT)

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OCT is a noninvasive imaging technique that uses light waves to capture high-resolution images of the retina. OCT can detect changes in the thickness of the retinal nerve fiber layer, which may be indicative of Alzheimer’s disease.

“Studies have shown that Alzheimer patients have loss of retinal ganglion cells that can be measured in the eye with optical coherence tomography,” said Dr. Daniel Laroche, director of Glaucoma Services and president of Advanced Eyecare of New York.

Glaucoma Exam

Even a routine glaucoma exam can offer clues about our risk for cognitive decline.

Patients with normal tension glaucoma were found to have a 52 percent greater risk of developing Alzheimer’s disease.

“Both diseases are associated with aging,” said Laroche. “In both conditions, the presence of inflammation can lead to T cell autoimmune damage and loss of retinal ganglion cells.”

He added that “healthy diet, exercise, and 15 minutes of meditation a day can delay development of both conditions.”

Ultra-Wide Field Fundus Photography

Fundus photography involves taking a magnified photograph of the back of the eye, including the retina and optic nerve.

A pilot study published in Ophthalmic Research found this can detect eye changes associated with Alzheimer’s disease.

Pupillometry

This measures changes in pupil size in response to light. In a study published in the journal Scientific Reports, researchers found that people with Alzheimer’s disease had a slower pupillary response to light compared to healthy individuals. This may be due to changes in the brain that affect pupil regulation.

The University of California is developing a smartphone app that checks pupil response, which might allow us to check our neurological health, including Alzheimer’s disease risk, at home.

“While there is still a lot of work to be done, I am excited about the potential for using this technology to bring neurological screening out of clinical lab settings and into homes,” study first author Colin Barry, an electrical and computer engineering doctoral candidate at UC San Diego, said in a statement.

It’s important to note that these methods are still in the early stages of development, and more research is needed to confirm their effectiveness in detecting Alzheimer’s disease.

Also, these methods are not a replacement for a clinical diagnosis of Alzheimer’s disease, which typically involves a combination of cognitive tests and medical imaging.