Alzheimer’s disease is an irreversible and progressive disease of the brain. For many Alzheimer's disease patients, the disease is not diagnosed until the person's memories and cognition have significantly deteriorated. Researcher Melanie Campbell from the University of Waterloo has discovered that an eye exam designed to detect the amyloid plaques at the back of the retina may be able to provide a much earlier diagnosis than physicians are currently able to provide to patients and their families. Additional findings from eye exams, including decreased retinal thickness and changes in how the retinal blood vessels respond to light are also early indicators of Alzheimer's disease.
There will be 1 million people with dementia in the UK by 2025. Alzheimer's disease is the most common cause of dementia, and there is no cure for it. The current tests for Alzheimer's disease are imperfect and rely upon a complex set of memory tests, physical exams and family history. The current set of tests is only accurate when the patient's disease has advanced. Early detection of Alzheimer's disease would allow patients and families to make plans for their care and would provide physicians and researchers with the opportunity to learn more about the progression of the disease and try out new treatments.
The nerve endings of the eye are a direct portal to what is happening in the brain. Researchers surmise that the amyloid plaques may leak into the nerve endings of the eyes from the brain tissue. The plaques could also be generated by the nerve endings themselves. The University of Waterloo researchers have developed a new type of eye test that is non-invasive and uses polarized light to detect the plaques within just a few minutes during a routine eye exam.
The polarized light technology also allows physicians and researchers to count and measure the size of the amyloid plaques, which current imaging systems are unable to do. The number and size of the plaques is associated with the progression of the disease. Although the testing has only been used on cadaver eyes for the testing period, the researchers hope to initiate clinical trials on volunteer patients soon.
In a similar study, researchers at the Florida State University and the Moorfields Eye Hospital in the UK measured the retinal thickness of retinal nerve fiber layers of 500,000 volunteers aged between 40 to 69 living in England. Of those people, 67,000 had eye exams. Of the 32,000 subjects who were not excluded due to other chronic health problems, 1,251 participants completed cognitive tests for a period of three years. The patients with thin 1,251 retinal nerve fiber layers were most likely to score lower on the tests, suggestion an association between retinal thickness and Alzheimer's disease.