Currently, there is no diagnostic test that definitively identifies individuals living with Alzheimer’s. The Alzheimer’s brain contains deposits of a protein called amyloid beta, which can only be tested following death. However, Alzheimer’s patients experience worsening difficulty with memory, language, and self-care, and an early diagnosis can mean more effective medical intervention. Melanie Campbell, professor of physics at the University of Waterloo, is looking for ways to get an early Alzheimer’s diagnosis by using the living eye as a window to the brain.
The brain is difficult to view directly, but the eyes are easier to access for medical imaging because they are transparent to light. Like the brain, the retinas at the back of the eyes are also part of the central nervous system. Campbell has detected amyloid beta deposits in the neural tissue of the retina, which is the light sensing layer at the back of the eye.
Campbell notes, “If we can develop this non-invasive method of doing the imaging which would be readily accessible to people, then early diagnosis of Alzheimer’s might be possible and that’s very important… it gets the patient involved in their care when the disease is still at any early stage. It also means that drugs that work best at early stage of the disease to slow down its progression can then be used.”
Although these tests are not yet being used on living patients, Campbell has already worked with donor tissue collected from patients after death. She knows that amyloid deposits are large enough to be imaged through the eye, and that they are usually present in individuals with confirmed Alzheimer’s disease. This makes a compelling case for early Alzheimer’s testing in the living eye.