Alzheimer's & Eye Sight: Is There a Connection? | Alzheimer's & Brain Awareness Month

Alzheimer’s disease, the most common type of dementia, is a progressive brain condition that gradually impairs thinking and memory. According to the National Institute on Aging, about five million people in the U.S. have Alzheimer’s. Unfortunately, there is no cure for the disease at this time.

While the exact cause of Alzheimer’s disease is not fully known, researchers have developed theories. ​
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Normally, signals traveling through neurons in the brain allow movements, thoughts, feelings, and memories to occur. In people with Alzheimer’s disease, scientists believe that certain proteins might become toxic to the brain and negatively affect the way the neurons function. Another theory involves vascular changes and how much blood and nutrients flow to the brain. 

Regardless of the exact cause, Alzheimer’s disease can affect all areas of a person’s life. Unfortunately, it leads to cognitive and memory issues and can cause physical problems as well.
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Can Alzheimer’s Disease Affect Vision?

Alzheimer’s disease can affect vision. Vision is a complicated process, in which visual information is sent from our eyes to our brain, where images are interpreted. Various factors contribute to how our brains interpret images, including memories and thoughts.
 
Alzheimer’s can affect vision in various ways. Certain diseases that affects the brain, including Alzheimer’s, can influence the brain’s interpretation of images being received by the eyes. In addition, vision problems, such as cataracts or changes in eyesight, can make it even more difficult for people with Alzheimer’s or dementia to navigate their world. Sadly, decreased visual perception can lead to misinterpretation of situations and create safety risks for people with Alzheimer’s and dementia.
 
Alzheimer’s disease, along with other forms of dementia, can have the following effects on vision:

• Problems with object recognition: People with dementia may see an object correctly with their eyes, but their brains may misinterpret what the eyes are seeing. As a result, people with Alzheimer’s may not be able to correctly or accurately name certain things or people they see.
• Poor color discrimination: There seems to be a connection between dementia and difficulties distinguishing between colors. People with Alzheimer’s disease may especially have problems recognizing colors in the blue-violet range.
• Decreased peripheral vision: It’s common for people with dementia to have decreased peripheral vision. Reduced side vision can lead to a variety of challenges for people with Alzheimer’s. For example, they may not notice objects to their side, leading them to bump into or trip over things as they walk. 

• Loss of depth perception: People with Alzheimer’s disease may gradually lose their depth perception. They may have problems distinguishing between flat pictures and three-dimensional objects or trouble judging distances.

 
There are also other types of dementia that affect vision. For example, posterior cortical atrophy is a rare form of dementia that causes vision problems without the presence of eye disease. While memory and cognitive problems tend to be milder than with Alzheimer’s disease, they can progress. Posterior cortical atrophy also tends to have an earlier onset than Alzheimer’s disease. Most patients start to have symptoms in their 50s and early 60s.
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Detecting Alzheimer’s Through Vision Tests

Although no vision test to definitively diagnosis Alzheimer’s disease currently exists, research is ongoing. One study published in Investigative Ophthalmology and Visual Science in 2016 indicated that changes in the retina might help diagnose Alzheimer’s disease. Although the study was conducted on mice, it indicated that changes to the retina occurred before behavioral changes were observed.
 
A more recent study published in Retinal Imaging in 2018 showed that adults with pre-clinical Alzheimer’s disease showed significant decrease in macular retinal nerve fiber layer (mRFNL) volume as compared to healthy adults on optical coherence tomography (OCT). OCT is part of a comprehensive eye exam, and mRFNL volume can be evaluated and monitored over time, giving clues about the presence, progression, or advancement of Alzheimer’s disease.
 
The retina holds additional promise for patients with Alzheimer’s disease. According to the American Academy of Ophthalmology, as Alzheimer’s disease begins, changes to the way light is reflected off the retina may develop. The hope is that those changes to the retina may be identified during a comprehensive eye exam, enabling early diagnosis of Alzheimer’s.
 
Additional research and testing continue in hopes that, one day, retina scanning could be a tool used to diagnosis Alzheimer’s disease early on in its progression. Early diagnosis enables treatment to start as soon as possible and may slow progression of the disease.
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Steps to Preserve Vision with Early-Onset Alzheimer’s Disease

Most people diagnosed with Alzheimer’s disease are over the age of 60. The incidence of certain vision problems, such as cataracts and macular degeneration, also increases with age. The combination of possible vision issues due to Alzheimer’s disease and age-related eye conditions can put vision at risk. Decreasing the risk of additional vision problems and managing present eye conditions is essential. Having your routine eye exams as prescribed by your eye doctor is also vital. Comprehensive eye exams help diagnose vision problems at their earliest stages.
 
Finally, maintaining a healthy lifestyle is also important for those with Alzheimer’s disease. Eating a healthy diet, including plenty of fresh vegetables and lean protein, and getting safe, regular exercise are good for overall health, including the health of the eyes.
 
We hope you found this article helpful. If you have any questions about Alzheimer’s disease, dementia, and vision changes or you would like to schedule an appointment with one of our eye doctors, please call our office at 508-746-8600.