Significant near-vision loss in older age may correlate with dementia risk, suggests new research that builds on the emerging potential for eye and vision health in detecting neurological disorders.
Presented at the International Conference on Alzheimer's and Parkinson's Diseases and Related Neurological Disorders 2017 in Vienna, Austria, the French analysis determined that 1 in 5 study participants—age 65 or older—registering moderate-to-severe near-vision loss at baseline went on to develop dementia within the next dozen years, as compared to only 1 in 10 with no vision loss. Such results drew mixed and skeptical reactions; however, proponents believe the results could help build evidence for a long-sought early warning flag for cognitive decline.
In this prospective, population-based cohort study using The Three-City Study data, 7,722 participants age 65 or older were tracked over the course of 12 years. At baseline, those participants presented as follows: 8.7% had mild near-vision loss (20/30 to 20/60), 4.2% had moderate-to-severe near-vision loss (20/60 or less) and 5.3% had distance-vision loss, per Medscape News.
Of those, 882 participants developed dementia over the course of the study, including 21.2% with moderate-to-severe near-vision loss, 17.1% with mild near-vision loss and 18.6% with distance-vision loss. Only 10.2% of participants with no vision loss developed dementia.
Even after adjusting for numerous variables, study authors note that moderate-to-severe near-vision loss still had a greater hazard ratio for dementia than did mild near-vision or distance vision loss.
Maryke Neiberg, O.D., associate dean of academic affairs at Midwestern University Chicago College of Optometry, who has written previously on optometry's role in Alzheimer's disease care, notes that patients typically do have difficulty with near-vision in the beginning stages of the disease, including crowding, alexia and figure-ground difficulties.
"Everyone has had the experience of an older patient with a bag of glasses, all about the same power, but the patient is happy with none of them," Dr. Neiberg writes. "This can often be the first indication of the problem."
Although vision changes naturally occur with age and don't always indicate a more serious condition, patients 60 years and older still should be wary of age-related eye health problems, sometimes occurring without early symptoms. Regular, comprehensive eye examinations are critical in senior years, and evolving understanding of neurological health frequently looks to the eyes as a bellwether.
Eyes into Alzheimer's, dementia?
Alzheimer's disease, a progressive, irreversible neurodegenerative disease, is the most prevalent form of dementia and accounts for an estimated 60-80% of dementia among Americans. It's characterized by the buildup of beta amyloid plaques and neurofibrillary (tau) tangles in the brain that affect normal functioning of cells, eventually causing a loss of brain tissue. Until recently, such buildup was only measurable post-mortem, but researchers are now using the eye as a proxy for neural health.
Now, researchers are investigating the use of spectral domain optical coherence tomography (SD-OCT) to determine a correlation between retinal nerve fiber layer thickness and cognition, as well as using hyperspectral imaging to detect retinal changes attributed to increased amyloid deposits. Both methods could provide an invaluable, noninvasive glimpse into the brain that utilizes methods—such as OCT—already employed in many doctors' offices.
"The doctor of optometry has an important role to play in the prevention and early detection of the ocular and visual changes that herald the onset of Alzheimer's disease," Dr. Neiberg wrote in a continuing education article for the California Optometric Association. "We have an even more critical role to play in the education of our patients and the public about the preventable risk factors that are associated with Alzheimer's disease."
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