According to a new study, people with Alzheimer’s disease have fewer blood vessels and less blood flow in the retina (back of their eye). These changes in the eye were found using a scanning technique called optical coherence tomography angiography (Octa). This test can show up blood vessels in the retina that are finer than the width of a human hair.
The discovery that the eyes of Alzheimer’s patients have these changes, has caused some to declare that an eye exam can detect Alzheimer’s in its early phases, but it’s too soon to say that it will lead to a simple test for Alzheimer’s. The research is still in the very early stages and doesn’t show whether the retinal changes occurred before or after the disease set in.
Also, the retinal changes may not be unique to Alzheimer’s patients, but might also be seen in people with other types of dementia, other eye conditions or medical conditions such as diabetes.
Study by Duke University
The study, which was published in the journal of the American Academy of Ophthalmology, was conducted by researchers from Duke University in North Carolina. It was a cross-sectional study that compared the eyes of participants over the age of 50 with and without Alzheimer’s during the same time period.
The study included adults with non-Alzheimer’s dementia, diabetes, high blood pressure, neurological conditions such as multiple sclerosis, glaucoma, age-related macular degeneration or poor vision. All of them had been diagnosed with either Alzheimer’s disease or mild cognitive impairment (MCI). Healthy people of the same ages were recruited from the community.
The study showed that people with Alzheimer’s have fewer blood vessels and less blood flow in the retina of their eyes, however, as it didn’t follow people over time, it can’t be definitely said that the retinal changes happened before or after they were diagnosed with the disease.
Conclusions from the Study
Researchers found that people with Alzheimer’s had fewer blood vessels and reduced blood flow, compared with both healthy controls and people with MCI. They also discovered that there were no differences in the blood vessels of MCI patients and the healthy controls.
The other notable finding was that the layer of nerve fibers that surround the optic nerve where it attaches to the retina was thinner in both Alzheimer’s patients and those with MCI, compared with the control group.
Researches suggest that the small changes in the tiny blood vessels of the retina may mirror small blood vessel changes seen in the brain.
While research increasingly links common eye conditions, such as glaucoma, age-related macular degeneration and diabetic retinopathy, to a risk for Alzheimer’s and other forms of dementia, more research is needed. Cataracts, another common age-related eye condition, had no apparent connection to a risk of dementia.
Adult Changes in Thought Study
The Adult Changes in Thought Study began in 1994 and included 5,400 dementia-free adults who were followed until they left the study, died or developed dementia. Researchers focused on 3,800 of those participants, both with and without eye disease at the start of the study. Over the course of the study, 792 people developed dementia.
Researches of this study found that people with age-related macular degeneration were 20 percent more likely to develop dementia as compared to people who didn’t have the eye disease. They also discovered that people with diabetic retinopathy were 44 percent more likely to develop dementia than those without. And, people in the study with a recent diagnosis of glaucoma, had a 44 percent higher rate of dementia.
Dr. Albert Hofman is the chair of epidemiology at the Harvard T.H. Chan School of Public Health. Commenting on the Adult Changes in Thought Study, Dr. Hofman says that glaucoma, age-related macular degeneration and diabetic retinopathy are all linked to cardiovascular disease. He suggests that the only known way to prevent Alzheimer’s and other forms of dementia is to prevent cardiovascular disease.
That means treating high blood pressure and cholesterol could be the key to protecting yourself from Alzheimer’s. If you have a family history of cardiovascular disease or cardiovascular-related eye diseases, you should be even more careful to control your personal risk factors.
Conclusion
Can an eye exam tell you if you are at risk for developing dementia in the future? Can it help to prevent dementia?
Someday, the answer to these questions may be yes. For now, eye exams are valuable in detecting early signs of eye disease so it can be treated, but they can’t yet predict your brain’s future health.
As Dr. Hofman suggests, the only known way to prevent Alzheimer’s and other forms of dementia to date, is to prevent cardiovascular disease. We need to do all the things we would do to prevent a heart attack or stroke.
