The eye is the only part of the brain that we can see directly — it harbors clues about brain health. Regular vision tests, experts say, could be key to early detection and prevention of dementia.
When was the last time you got your vision checked?
Routine screenings could spot cataracts and other eye diseases early, keeping vision loss minimal. There’s another unexpected benefit — the Lancet Commission, a global network of dementia researchers, recently identified vision loss as a modifiable risk factor for dementia.
The Lancet Commission linked untreated vision loss, which affects one in eight people over 50, to a 47-percent increased risk of developing dementia. (To put that percentage in perspective, about 200 out of 10,000 older adults without vision problems will develop dementia compared to 249 with untreated vision loss.)
Experts say routine vision testing could help doctors spot who’s at risk and make an early diagnosis. And some are optimistic that treating vision loss could reduce the risk of developing dementia as well.
What causes vision loss?
As we age, visits to the eye doctor become routine. They may be the first to spot vision loss, which can be a sign of other health problems.
Cataracts, the most common form of vision loss, occur when proteins build up in the eye’s lens, causing vision to become progressively blurry and cloudy.
Eye doctors also measure eye pressure to check for a condition called glaucoma. Glaucoma is caused by fluid buildup in the eye. High blood pressure is a significant risk factor for both dementia and glaucoma.
Eye doctors can also take a look at the eye’s blood vessels. High blood sugar levels damage the eye’s blood vessels, leading to the growth of new abnormal ones. Untreated diabetes can cause a condition called diabetic retinopathy, which leads to further eye damage and vision loss.
After spotting these signs, the eye doctor may refer you to an endocrinologist who can treat diabetes and reduce the risk of developing dementia. A class of diabetes drugs called GLP-1 agonists may also prove effective for treating symptoms — Novo Nordisk is testing the active ingredient in Ozempic and Wegovy in Phase 3 trials.
In other cases, you might experience vision problems when there’s nothing wrong with the eye. Visual symptoms precede memory or thinking problems in dementia. In posterior cortical atrophy, a subtype of early-onset Alzheimer’s, the first symptoms include blurred vision, visual hallucinations, and difficulty reading.
An eye doctor can refer their patients to a neurologist who can check if they have PCA. Getting a diagnosis sooner allows people to participate in clinical trials, try approved Alzheimer’s treatments, and plan for their future.
In the future, a routine eye test could be used even earlier to test whether someone is at risk of developing Alzheimer’s. Scientists say the earliest signs of the disease might appear in the eye some 20 to 30 years before cognitive symptoms start.
Maya Koronyo-Hamaoui, a professor at Cedars-Sinai Medical Center, is developing retinal scans that could quickly spot the earliest signs of the disease: “The retina is the only central nervous system organ not shielded bone that can be imaged directly and repeatedly,” she told Being Patient.
Can treating vision loss prevent dementia?
Vision loss may be a cheap, modifiable risk factor for dementia. But getting a definitive answer is tricky.
One Korean study that looked at more than six million people in a dementia database found that people with more severe visual loss had a higher risk of developing dementia. This study suggests that vision loss and dementia pathology are linked, so treating vision loss might also prevent dementia, but more research is needed.
High blood pressure and diabetes increase the risk of developing conditions that cause vision loss, as well as dementia. That makes it hard to tell whether the benefits of treatment come from preventing vision loss or getting blood pressure or blood glucose under control (or both).
Even for cataracts, the evidence is mixed. Surgery is a routine intervention for restoring vision, but it is unclear whether it also reduces the risk of dementia.
One study followed 3,038 adults over 65 with cataracts for over 20 years to see if they developed cognitive decline. Those who had their cataracts removed had a lower dementia risk. However, a UK study of 300,823 older adults found that cataract surgery did not reduce the risk of developing dementia.
The bottom line? Spotting the earliest signs of vision loss could clue you in on other health conditions that raise the risk of dementia. Treating vision loss ensures a higher quality of life, and although the evidence so far is uncertain, it might reduce the chances of developing dementia.
