The expression “eyes are the window to the brain” is true in many ways. Our eyes are the only place in the entire body where you can directly view one of the brain’s 12 cranial nerves (optic nerve). Researchers studying the connections between the eyes and the brain have uncovered interesting information about aging and dementia. We’ll review some of these discoveries in this article.

What Is Dementia?

Dementia is a general term for the impaired ability to think, reason, and remember. The impairment typically progresses over time. Although the average age of onset is 83 years, dementia can occur in younger people.

Contrary to what some people think, dementia is not a normal part of aging and results from disease or injury that affects the brain. Some signs of dementia are:

  • Getting lost in a familiar area 
  • Forgetting names of family members
  • Having trouble completing everyday tasks
  • Repeating questions
  • Using unusual words to refer to typical objects

The most common cause of dementia is Alzheimer’s disease. Other major types of dementia include vascular dementia, Lewy body dementia, and frontotemporal dementia. Stroke or traumatic brain injury can also lead to dementia. 

Dementia affects over 55 million people worldwide, with an additional 10 million cases per year. With the population living longer than ever before, the number of people with dementia continues to grow. Currently, there is no cure for most types of dementia, so reducing risk or delaying the onset of symptoms is increasingly important.

Model of the brain

Visual Impairment and Dementia

Visual impairment is more common in older adults with dementia than those without. Some of these issues are related to visual processing, which is the brain’s ability to process visual information. Even if the eye is healthy, vision can be affected if there is brain damage.

Some vision problems related to dementia include:

  • Decreased contrast sensitivity
  • Decreased color vision
  • Poor spatial awareness (being aware of your position in relation to your surroundings)
  • Poor depth perception
  • Misidentifying objects or people (mistaking something for a different object)
  • Hallucinations

Since people with dementia are typically older, they also have an increased risk of cataracts, glaucoma, macular degeneration, and other age-related eye diseases. These issues can lead to further vision loss.

Additionally, vision loss may cause people to become more isolated, decrease physical activity, and reduce social interaction. All of these are risk factors for dementia. 

Cataract Surgery and Dementia Risk

A recent study found that cataract removal is associated with a lower risk for dementia. The study followed approximately 3,000 patients over 24 years. Patients who underwent cataract surgery had a 30% decrease in their risk for dementia

However, researchers note that more studies are needed to understand how cataract removal affects dementia. Since cataracts are a common source of vision loss, cataract surgery may help reduce risk factors for dementia and improve quality of life in older patients.

Eyeglasses and visual acuity chart

Early Detection of Dementia

Early stages of dementia are challenging to diagnose since the symptoms can be similar to normal, age-related changes. In addition, cognitive function testing (screening tests used to diagnose dementia) may not always be reliable. These issues often lead to a delayed diagnosis.

Fortunately, researchers are looking into objective methods to detect Alzheimer’s disease early on. When Alzheimer’s disease develops, many changes take place before any symptoms begin to show. Interestingly, one of the places scientists can detect change is in the eye.

Blood Flow Changes

In many ways, the eye is an extension of the brain. They both have high metabolic demands, which means they require a steady supply of blood flow and oxygen. This is particularly true for the retina, which is the light-sensing tissue lining the back of the eye. 

When the retina detects light, it signals the brain to increase blood flow to the eye. Research shows that in people with Alzheimer’s disease, this response is altered. 

Oxygen Saturation

Another area scientists are looking at is oxygen saturation in the retina, which measures the eye’s oxygen supply. Many diseases are associated with reduced oxygen in the retina, including Alzheimer’s disease. 

Researchers believe that measuring blood flow changes and oxygen saturation can help diagnose dementia at early stages and track the disease as it progresses over time. Hopefully, the technology to measure these changes will become widely available in the future. With early detection, patients can get treatment to manage symptoms before their dementia worsens.

Impact of Dementia and Vision Loss

Dementia significantly affects quality of life for the patient and their family, particularly when eye issues are also present. Dementia and vision loss have overlapping symptoms, making it difficult to differentiate between them.

If a loved one has been diagnosed with Alzheimer’s disease or other conditions associated with dementia, here are some signs to look out for:

  • Difficulty reading or avoidance of reading, even with glasses
  • Problems recognizing people 
  • Increased falls or trips
  • Increased disorientation
  • Difficulty transitioning between light and dim areas
  • Difficulty locating objects or food on a plate
  • Increased dependence on others

Have your loved one receive a comprehensive eye exam if you notice any of these issues. The optometrist can help uncover whether the issue is related to an eye health or vision problem and prescribe glasses to maximize existing vision. They can also refer your loved one to a low vision clinic, which helps people with visual impairments function better in their daily lives.

Please don’t hesitate to contact our practice with any questions or schedule an eye exam for you and your loved ones!