Call it a puzzle, a labyrinth, a computer or one of the most beautiful mysteries in the world: the human brain and its capacity for emotion, critical thinking, wonder and communication is complicated, to say the least. When disease chips away at the mind’s capacity for those things, the consequences can be devastating.
It’s no wonder, then, that we spend a lot of time untangling links and trying to unearth different risk factors for dementia, the umbrella term for symptoms that impact thinking, memory, language and communication. One factor that’s been brought to surface recently is vision.
A July study published in JAMA Ophthalmology found that having visual impairment (which includes things like trouble seeing from a distance, problems seeing up close or contrast sensitivity issues when you’re not wearing glasses) was linked to a higher likelihood of dementia in adults who were in their 70s and up. And the more vision issues a person had, the higher the risk seemed to be. This builds on what doctors and researchers already know about dementia and vision problems: that vision problems and dementia are more likely to occur in older adults, that dementia can sometimes affect a person’s ability to see or process what they see, and that there is a relationship between problems seeing and dementia.
But do vision problems directly lead to dementia? According to Dr. Ronald Benner, president of the American Optometric Association, it’s important to distinguish between vision acuity, which is how sharply you can see objects, and vision in general, which is how we process sensory information, to get the full picture on any link between dementia and vision.
We normally consider vision “just the eyes,” Benner said, “but it’s really the visual system is the eyes collecting information and then the brain processing it.”
“Acuity is only one measurement of vision,” he added. “We don’t want to get that confused with ‘I have a loss of visual acuity, I can’t read the smallest letter on the line, ‘I have dementia.'”
Vision is also one way we connect to the world and receive sensory information. And according to Heather Snyder, vice president of medical and scientific relations at the Alzheimer’s Association, it’s just one part of sensory health that’s been associated with dementia. Other changes to the way the brain takes in information — through our hearing, touch and even smell — have also been linked to cognitive decline. Snyder pointed to research presented at the Alzheimer’s Association in 2019 linking multiple sensory impairments to dementia risk in older adults.
“For now, these connections are all associations — we do not know if there is a cause and effect,” Snyder said in an email. “More research is needed to understand why or how visual impairment is associated with the brain’s health.”
How sight works, and how it may overlap with dementia symptoms
In a nut shell, our eyes work by taking in light that passes through the cornea and the lens, then bringing it into focus; the light eventually hits the retina, which has cells that convert the light into electrical signals that go back to the brain through the optic nerve. People who have vision impairment from nearsightedness, for example, have a disruption in this process due to the eyeball itself, and it can be corrected with glasses or contact lenses.
Other health conditions of the eye, like cataracts, can also impact sight but require surgery for treatment. Research from 2021 found that people who had cataract removal surgery had a nearly 30% lower risk of developing dementia compared to those who didn’t have their cataracts removed.
Dementia itself can also impact vision if it affects the part of the brain responsible for visual processing. Additionally, some health conditions that affect other parts of the body may be seen in the eye first, like diabetes and high blood pressure (which, coincidentally, have also been linked to dementia risk).
The prevalence of vision problems among older adults and dementia patients may make it hard to tell if someone with dementia is having trouble recognizing a person because of the dementia or because their glasses prescription is way outdated.
But is there a strong enough link between vision loss and dementia to suggest that preserving your eye health will ward off dementia? There’s no data clearly linking cognitive health to vision health, according to Dr. Andrea An, medical director and head neurologist at Neurology Associates Neuroscience Center in Arizona, adding that vision preservation is “an issue fraught with uncertainties.”
“That being said, the effects of dementia can be more severe if there is associated vision loss,” An explained in an email. “The impaired vision can cause a lot more disorientation and confusion.”
This may also make it seem that someone’s dementia symptoms are worse than they actually are if they’re unable to see well, she noted.
Snyder noted that there could be ways in which vision problems impact the results of a test of dementia symptoms, as many rely on sight to conduct them.
“Especially as one ages, this is an important discussion to have with your health care provider to ensure that any type of test is being properly and effectively conducted,” she added.
Vision as a path for communication and connection
Social isolation has been identified as a risk factor for dementia. If someone can’t see well, they may pull back from activities they used to enjoy. This may lead to symptoms of depression or anxiety, which are risk factors for cognitive decline, Snyder said.
“Having poor vision may result in a withdrawal from these activities, and social isolation is known to increase the risk of depression and anxiety,” she said.
Dr. RJ Tesi, CEO and chief medical officer of INmune Bio, a clinical-stage immunology company, said in an email that studies have suggested mental and social activities can delay cognitive decline, which would include “brain exercises” such as reading, games and crossword puzzles.
If poor vision is preventing you from doing these things, Tesi said, “then it is a short jump to suggest that poor vision contributes to dementia.”
As many as one-fourth of older adults age 65 and up are may be considered socially isolated. This means the relationship between being socially isolated and vision problems may be even more impactful. For example, in some cases someone may know they have a problem seeing, but they don’t have a way to correct their vision because they don’t have someone to take them to the eye doctor or they don’t see the point of it.
Hearing is closely connected to our capacity for language and communication, and losing communication can “negatively impact cognition and overall health,” Snyder said. But more research is needed to see whether there’s a similar link between vision and cognition, she said. Research has recently supported the case for treating hearing loss with a hearing aid in order to reduce dementia risk.
Correcting your vision benefits your overall health
While there would be more considerations to address with a doctor before recommending an older adult go through eye surgery, for example, to potentially reduce dementia risk, there’s no reason you shouldn’t stay up to date on your glasses prescription or avoid your annual eye exam.
Benner stressed the importance of regular eye exams. In addition to any potential cognitive benefits of correcting your vision, a doctor may be able to detect other health problems, like high blood pressure, diabetes and stroke. Annual, comprehensive exams are recommended for older adults, but anyone who’s having trouble seeing or who has a prescription for glasses or contacts should be checked regularly.
“Often time the eyes do manifest initial diseases in the body,” Benner said. “It’s so very important that people get in for their routine vision care.”
Read more: Get Affordable Eye Exams and Glasses Without Insurance
