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Cognitive Function, Dyslexia, And The Vision Connection

posted by Elizabeth Klunk, RN, BSN, CCM-R, SVP Medical Management, Versant Health

on October 3, 2019

There’s no question annual eye exams are critical for vision and eye health, but their benefits go well beyond ocular health. A routine exam is not only an early detection strategy for eye health, but overall health as well.

In fact, like cardiovascular health, there is also a link between vision and brain function, most notably cognitive function and dyslexia.

Visual Impairment and Cognitive Function

According to a 2017 study, seniors with visual impairment were up to 2.8 times more likely to have cognitive dysfunction or dementia. In the study, researchers looked at two different nationally representative samples of the U.S. population – the National Health and Nutrition Examination Survey (NHANES), 1999-2002, and the National Health and Aging Trends Study (NHATS), 2011-2015.

Researchers found that approximately 25% of the groups studied had cognitive impairment. Additionally, 30% of the NHANES group considered their eyesight fair to poor, while 10% of the NHATS group noted visual impairment.

When researchers assessed these results, they found that visual impairment was associated with the worse cognitive impairment scores. Moreover, those people with near vision impairment were 3.1 times more likely to have cognitive dysfunction, even when other factors such as diabetes, heart disease, smoking, etc., were taken into consideration.

Researchers concluded that there was a clear connection between vision impairment and poor cognitive performance. More specifically, they found that “self-reported [visual impairment] was associated with 1.9-fold to 2.6-fold increased odds of dementia.”

This can have a cost implication as well. Researchers found that cost of care significantly increases among Medicare beneficiaries who had severe vision impairment, according to a study from JAMA Ophthalmology. Specifically, those Medicare enrollees with severe vision loss, as compared to those with no vision loss, had 4% longer mean hospital stays, 22% higher likelihood of readmission, and 12% higher costs. When these findings were extrapolated out to hospitalization of patients with vision loss nationwide, it was estimated that more than $500 million in additional costs were spent caring for people with severe vision loss each year. That is a staggering figure!

Dyslexia, Vision, and Eye Symmetry  

On the other end of the spectrum, eye exams have also been able to detect dyslexia in both children and adults. Dyslexia, a miswiring of the brain pathways that serve vision, reading and comprehension, is thought to exist at birth. Sadly, it is often only diagnosed in later childhood in the context of poor school performance, and its association with poor self-esteem and anti-social behavior.

Fortunately, an early eye examination is a critical component in the diagnosis and management of children with learning disorders. According to a 2017 study, people with “normal” reading ability have a dominant eye, while people with dyslexia do not.

Researchers found that people with dyslexia tend to have symmetrical eyes, meaning that their retinas as well as the way they transmit visual information to the brain is symmetrical. This differs greatly from people who read more comfortably. In these cases, not only are the retinas asymmetrical, often with one eye more dominant than the other, but the way visual cues are sent to the brain are also asymmetrical.

This is yet another way an eye exam can give us some clues into whole body health, including cognitive function and brain health.

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