We see everything through our eyes. But can we see our brain through our eyes? Researchers and ophthalmologists say that the eyes can be windows to the brain.
Researchers claim that changes happening in the brain could be seen through a simple, routine, non-invasive eye exam. They claim that eye exam can be particularly useful in identifying the early changes of Alzheimer’s disease several years before the onset of symptoms.
Alzheimer’s disease is the most common form of dementia, accounting for around 60 to 80 percent of cases. The condition is characterized by progressive decline in memory and thinking, as well as changes in mood and behavior, that affect a person’s ability to live independently.
It is estimated that around 564,000 Canadians are currently living with a diagnosis of dementia. This number is expected to increase to 937,000 in about 15 years.
While research into the precise causes of Alzheimer’s is ongoing, scientists know that the condition involves the degeneration and death of brain cells. The buildup of beta- amyloid protein outside the brain cells and tau protein inside the cells – is considered a key process in the evolution of the disease. As of now, beta-amyloid plaques and tau tangles are considered hallmarks of Alzheimer’s.
Beta-amyloid is a sticky fragment of the amyloid precursor protein – a protein normally present in the brain. In Alzheimer’s disease, these beta-amyloid fragments clump together, forming “plaques” in the brain that disrupt communication between nerve cells and trigger immune cell activity. This along with the tau protein tangles leads to inflammation and brain cell death.
It is believed that these changes start happening in the brain 15-20 years before the person experiences the first symptom of memory loss. It is usually after these changes are well- established in the brain that a person would get diagnosed and therefore, the currently available medications tend to be ineffective for most people with Alzheimer’s disease.
Efforts have been ongoing to develop techniques to facilitate early diagnosis of the disease. At present, the only way to detect the presence of beta-amyloid and tau tangles is to use PET scan or do a spinal tap to detect the presence of beta-amyloid and toxic tau in the cerebrospinal fluid. However, such techniques are invasive, expensive and inaccessible, making population-wide screening challenging.
In 2017 researchers Maya Koronyo-Hamaoui, Ph.D., of the Maxine Dunitz Neurosurgical Institute in Los Angeles, and colleagues reported that amyloid plaques associated with Alzheimer’s disease can be detected in the retina (image-forming part) of the eye. Using a non-invasive auto-fluorescent imaging technique and a high-resolution ophthalmic camera the researchers were able to detect high levels of beta-amyloid plaques in the retinas of patients with Alzheimer’s disease, compared to healthy individuals.
In a new study, researchers from Washington University discovered that people with high levels of amyloid plaques in the brain and consequent high risk of developing Alzheimer’s disease had thinner retinas as well as fewer blood vessels indicating reduced circulation to the eyes and the brain. More research is needed to confirm the link between retinal thinning and Alzheimer’s disease.
However, if these findings get verified in future studies, we would have a quick, non-invasive, and inexpensive eye exam to screen for Alzheimer’s. This will enable physicians to diagnose the disease early and administer treatment early to delay further damage.
In another study, researchers from the University of Washington School of Medicine found that people with age-related macular degeneration, diabetic retinopathy and glaucoma have approximately 50% higher risk of developing Alzheimer’s disease. The results do not imply that people with these eye conditions will definitely develop Alzheimer’s disease. Instead, it advises physicians to check their patients with these eye conditions for memory loss or dementia.
How are these studies relevant for us? If you have any of these eye conditions, you can request your physician to monitor you closely for cognitive impairment. Secondly, if the specialized retinal exams become available, we will have a simple, non-invasive and inexpensive method to facilitate early diagnosis and treatment of Alzheimer’s disease.
Padmaja Genesh, who holds a bachelor degree in medicine and surgery as well as a bachelor degree in Gerontology, has spent several years teaching and working with health care agencies. A past resident of Red Deer, and a past board member of Red Deer Golden Circle, she is now a Learning Specialist at the Alzheimer Society of Calgary. Please send your comments to padmajaganeshy@yahoo.ca