A visit to your eye care professional may give you clues about the health of your brain and reveal some early signs of various forms of dementia, including Alzheimer’s disease.
Alzheimer’s disease is a degenerative neural disease caused by an abnormal build-up of proteins in the brain that kills cells and damages connections between neurons. Common symptoms include memory loss, difficulty thinking, disorientation, and other kinds of cognitive decline. Symptoms can also include vision problems such as decreased peripheral vision and trouble with spatial relationships, object recognition, color discrimination, and depth perception.
Alzheimer’s also has a significant financial impact, leading the pack on Medicare reimbursement. One in every five Medicare dollars goes to someone with the disease.
In the U.S., an estimated 5.5 million people may be living with Alzheimer’s disease, according to the National Institute on Aging. By 2060, the number of Americans with Alzheimer’s is expected to nearly triple to 15 million. Currently, Alzheimer’s is typically only diagnosed during an autopsy. If a routine eye exam could help to predict Alzheimer’s long before a person shows symptoms, doctors would have more time to slow the progression of the disease.
Routine eye exams are critical for not just vision and eye health, but also to detect a myriad of other health conditions, ranging from cognitive dysfunction and inflammation to cardiovascular disease and diabetes. In fact, when a patient receives an eye exam, the doctor actually gets a non-invasive look inside the body, giving the physician a chance to detect many of today’s most feared health conditions, often long before symptoms appear.
The secret lies in the exam itself. When eye doctors perform an exam, they not only test visual acuity, eye movement, and side vision, but they also check eye pressure, the topography of the eye, and your retina and optic nerve. In doing so, an ophthalmologist or optometrist can see characteristic signs of damage to the retinal blood vessels that reflect system-wide abnormalities affecting the brain, heart, and more.
The eye-brain connection
A 2017 study found that seniors with visual impairment were up to 2.8 times more likely to have cognitive dysfunction or dementia. The difficulty of diagnosing Alzheimer’s disease and other dementias is driving research on the eye-brain connection. Both vision and cognition decline with age, leading to the question of whether and how they are related. Although no vision test to definitively diagnose Alzheimer’s disease currently exists, promising research is ongoing, an abundance of which shows a link between eye health and brain health and could help screen for Alzheimer’s disease.
For example, a recent study showed that people who have macular degeneration, glaucoma, or diabetic retinopathy are more likely to be diagnosed with Alzheimer’s disease than people without these conditions. All three of these conditions are degenerative — meaning they get worse over time. And all three are more common as people age.
The 2018 study, from the University of Washington and the Kaiser Permanente Washington Health Institute, tracked a random sample of people age 65 and older for five years. Participants with one or more of these eye conditions had a 40 to 50 percent greater risk of being diagnosed with Alzheimer’s disease than the others. While the research did not show cause and effect, it did show there is a connection.
In addition, research published in Alzheimer’s & Dementia in 2019 analyzed data drawn from the Adult Changes in Thought study. The researchers focused on 3,800 of those participants, both with and without eye disease at the start of the study. Some 792 of them went on to develop dementia. Study authors found that people with age-related macular degeneration were 20 percent more likely to develop dementia compared with people who did not have the eye disease. People with diabetic retinopathy were 44 percent more likely to develop dementia than those without. People in the study with a recent glaucoma diagnosis — but not participants with established disease — had a 44 percent higher rate of dementia. It’s not clear why there was a difference between people with new or existing diseases.
A study of over 200 people by the Duke Eye Center found that cognitive differences pointing to dementia can show up in the density of blood vessels in the eyes. The researchers found that the Alzheimer’s group had fewer small retinal blood vessels in the back of the eye and that a layer of the retina was thinner. People with mild cognitive impairment did not show these changes. The researchers hypothesized that the small changes in the blood vessels may mirror small blood vessel changes in the brain.
These studies highlight how eyes are connected to the rest of the body—including the brain—and can therefore provide a window into general health. The optic nerve and retina are actually brain tissue that extends outside the brain. Alzheimer’s disease and dementia, which are caused by damage to brain cells, both appear to have effects on the retina.
More research is needed on the connection between eye and brain health, but results of the early research are very promising. The American Academy of Ophthalmology recommends a baseline eye exam starting at age 40. In addition to evaluating eye health and vision, these exams can help detect more than 30 chronic health conditions, including dementia and Alzheimer’s disease. Communication between eye care professionals and primary care physicians can help ensure these conditions are addressed in their early stages when they are most treatable.
- http://act.alz.org/site/DocServer/2012_Costs_Fact_Sheet_version_2. pdf?docID=7161
- Chen SP, et al. Association of vision loss with cognition in older adults. JAMA Ophthalmol. 2017;135(9):963-70.