A new diagnostic tool that can identify Alzheimer’s disease long before the onset of symptoms was presented at the 2016 Alzheimer’s Association International Conference (AAIC) in Toronto.
Alzheimer’s disease is notoriously difficult to diagnose and nearly impossible to catch early. This could soon change with a new type of non-invasive eye scan developed and patented by Professor Melanie Campbell, from University of Waterloo’s Department of Physics and Astronomy. It uses polarized light to highlight deposits called amyloid proteins found at the back of patients’ retinas decades before they experience cognitive decline.
“Polarization imaging is promising for noninvasive imaging of retinal amyloid deposits as a biomarker of Alzheimer’s,” Campbell said. “The ability to detect amyloid deposits in the retina prior to disease symptoms may be an essential tool for the development of preventative strategies for Alzheimer’s and other dementias.”
In order to diagnose Alzheimer’s disease and other forms of dementia, doctors currently rely on either a combination of late-stage symptoms and expensive positron emission tomography (PET) brain scans or tests on the brain after death. The new method would give a less expensive, more available alternative to PET.
Campbell’s research, in collaboration with colleagues at the University of Waterloo, UBC, Vivocore Inc, InterVivo Solutions, and the University of Rochester and Massachusetts General Hospital, establishes her diagnostic method’s proof of concept in both human and an animal model. She shows polarized light scans are as sensitive as other more established methods and can be done cost-effectively without using irritating dyes, making it potentially useful as an in-office screening tool.
“Amyloid proteins are made up of protein fibers with different refractive indices along and across the fibers,” said Campbell, also a professor in the School of Optometry and Vision Science. “They light up the same way as when scotch tape is placed between two polarizing filters. While other researchers thought that a dye was needed to make the protein visible, we were able to achieve the same results using optics and additional computer processing.”
Amyloid beta protein deposits in the brain have been proven to be present in patients decades before they experience symptoms of the disease. Although the reasons this protein appears are still being debated, the fact that it also deposits in the retina, an extension of the brain, means these deposits can be used as a biomarker for diagnosing Alzheimer’s disease long before symptoms appear.
“Early diagnosis is important, especially since treatment options are more limited later in the disease,” Campbell said. “Widely available, inexpensive, early detection of amyloid would help researchers develop more effective treatments before the onset of symptoms.”