Alzheimer’s disease is a common form of dementia that causes progressive brain damage, leading to memory loss and cognitive decline. Advanced age is the primary risk factor for this disease.

While there’s no cure, early detection can help manage its progression and prompt people to engage in brain-boosting activities like learning a new language.

Since Alzheimer’s affects the brain, it can also affect vision. In fact, according to a 2022 study, about 1.8% of dementia cases in the United States are linked to vision problems.

That said, a specific type of eye exam can detect changes in the retina that may signal Alzheimer’s disease.

Read on to learn about Alzheimer’s, how eye symptoms can be detected, and what they mean.

Research suggests that changes in the brain associated with Alzheimer’s may affect the retina of the eye.

The retina has 10 layers that play a key role in visual perception by relaying information from the eye to the brain, integrating signals, and detecting motion, brightness, and color.

Changes in the retina may mirror the effect of Alzheimer’s on the brain because the optic nerve connects directly to the brain, allowing the transfer of amyloid precursor proteins (APPs). This may result in visual changes and symptoms such as:

  • difficulty reading
  • difficulty distinguishing colors or recognizing objects
  • difficulty perceiving motion
  • loss of peripheral vision
  • difficulty recognizing emotional facial expressions

If you routinely see an ophthalmologist, you’re probably used to getting standardized eye exams that assess vision and look for conditions like glaucoma and macular degeneration.

However, these tests do not analyze the eye for evidence of Alzheimer’s disease.

Optical coherence tomography angiography

A relatively new, noninvasive imaging test called optical coherence tomography angiography (OCTA) allows your ophthalmologist to view tiny blood vessels in the back of your eye.

This exam involves taking 3D images of blood vessels in the eye. Your optometrist or ophthalmologist will ask you to look at a small image while the machine scans your eye without touching it.

This test then assesses:

  • deterioration in the retina
  • disparities in blood vessel density
  • capillary blood flow

After the exam, your eyes may be dilated and light-sensitive, so it’s recommended that you wear sunglasses if needed.

How OCTA can indicate Alzheimer’s

A 2022 review of multiple studies on Alzheimer’s disease found that the changes in retinal blood vessels identified by the OCTA test may be a biomarker for early Alzheimer’s disease. Researchers noted that a deterioration in the blood vessels of the retina occurs when similar changes are happening in the brain.

In another 2021 study, researchers identified a rise in blood flow through the retina’s capillaries and an irregularity of this flow compared to control subjects. These results suggest that this greater blood flow may be a characteristic of early stages of Alzheimer’s. However, this was a small study with only 21 human subjects, and more research is needed to verify this.

Other detection

While more studies may be needed to verify this, it’s worth noting that dementia may affect visual processing long before other symptoms appear.

A 2024 study found that visual sensitivity may decline years before a dementia diagnosis. After examining over 8,000 healthy people in England, researchers discovered that those who eventually developed the disease had a slower reaction time when trying to identify a triangle among moving dots on a screen.

This suggests changes in visual perception could be an early indicator of dementia than previously believed. However, researchers in this study admit that the visual sensitivity test has low sensitivity and specificity.

Are Alzheimer’s disease and dementia the same thing?

Dementia is an umbrella term that refers to deficits in mental ability severe enough to interfere with daily life. There are many different types of dementia.

Alzheimer’s disease is the leading cause of this condition. However, not everyone with dementia has Alzheimer’s disease.

What is the dementia stare?

The dementia stare may refer to a symptom of dementia that involves staring into space. This may also include what’s known as glassy eyes or reduced gaze, in which one is unable to move one’s eyes normally.

Emerging evidence indicates that changes in the eye, including in the retina and retinal capillaries, may serve as potential biomarkers for Alzheimer’s disease.

The optical coherence tomography angiography (OCTA) test, a specific type of noninvasive eye exam, can be used to identify retinal changes that may indicate early Alzheimer’s disease.

While compelling, more research is needed to determine if this test can be used to diagnose Alzheimer’s in people who have it prior to the appearance of symptoms.