eye test alzheimer's

More Evidence An Eye Test Holds Clue To Alzheimer’s Risk

By Deborah Kan | September 13th, 2019

Recent studies suggest that an eye test could reveal how likely a person is to develop Alzheimer’s disease (AD) later in life. Scientists at the University of California San Diego now say the secret to assessing risk may lie in the way your pupils dilate.

Eye Test to Determine Alzheimer’s Risk

In a new study published in the Neurobiology of Aging, researchers found that measuring how quickly a person’s pupils dilate while taking cognitive tests may be a low-cost and low-invasive way to screen high risk patients before cognitive decline sets in.

Pupillary responses are driven by a cluster of neurons in the brainstem known as the locus coeruleus (LC.) It is responsible for regulating arousal and also modulating cognitive function. The LC is also the earliest known area where tau protein, a commonly known biomarker of Alzheimer’s disease, appears. Tau is more strongly associated with cognition than amyloid beta plaques, another early hallmark of the disease.

The LC regulates the changing diameter of the eyes’ pupils during cognitive tasks (pupils get bigger the more difficult the brain task). In previously published work, the researchers had reported that adults with mild cognitive impairment, often a precursor to Alzheimer’s, displayed greater pupil dilation and cognitive effort than cognitively normal individuals, even if both groups produced equivalent results. Critically, in the latest paper, the scientists link pupillary dilation responses with identified Alzheimer’s risk genes.

“Given the evidence linking pupillary responses, LC and tau and the association between pupillary response and AD polygenic risk scores (an aggregate accounting of factors to determine an individual’s inherited AD risk), these results are proof-of-concept that measuring pupillary response during cognitive tasks could be another screening tool to detect Alzheimer’s before symptom appear,” said William S. Kremen, lead author and professor of psychiatry at UC San Diego School of Medicine.

Recent Research Indicates The Eyes Could Unlock Clues to Early Detection

Alzheimer’s disease begins to alter and damage the brain years, or even decades, before symptoms appear. This makes early identification of AD risk paramount to slowing its progression.

This study follows a similar recent report from the Boston Medical Center where scientists analyzed the eye fluid of 80 patients scheduled to undergo eye surgery. They tested the fluid for the protein markers, then compared those levels to results of a baseline cognitive test. Levels of the proteins were associated with lower cognitive scores among the patients.

Researchers at Duke University have also used special imaging to scan the eyes of people with Alzheimer’s, people with mild cognitive impairment (often considered a precursor to Alzheimer’s) and healthy people. Changes in small retinal blood vessels in people with Alzheimer’s were present compared to the healthy cohort.

With 100 million expected to develop dementia in the next 30 years, recent eye studies are looking for a cheaper and faster way to detect Alzheimer’s disease in order to bolster efforts on early stage prevention and treatment.

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