A Canadian researcher has developed a non-invasive way to test for Alzheimer’s disease years before a patient begins to show symptoms – and all it takes is a simple eye scan.

Alzheimer’s disease can be difficult to diagnose, and doctors have typically relied on expensive brain scans and the onset of symptoms to identify the progressive, irreversible disease.

But a University of Waterloo researcher says her newly-developed diagnostic method could spot early warning signs of the disease in a patient’s eye, allowing time for treatment to delay its onset.

“Early diagnosis is important, especially since treatment options are more limited later in the disease,” Melanie Campbell, director of the Guelph-Waterloo Physics Institute, said in a press release.

The new method works by using polarized light to highlight deposits within the eye call amyloid proteins. Amyloid proteins are considered a biomarker of Alzheimer’s and have been found in some patients years and even decades before they show symptoms of the disease.

Medical experts haven’t reached a consensus as to why amyloid proteins appear before Alzheimer’s, but locating the deposits in the retina could change the way doctors test for the disease.

“Widely available, inexpensive, early detection of amyloid would help researchers develop more effective treatments before the onset of symptoms,” Campbell said.

The method is particularly exciting for researchers because it doesn’t involve using dyes to highlight the proteins.

“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,” Campbell said.

Plenty of collaborators were involved in the research, including Campbell’s colleagues at the University of Waterloo, the University of British Columbia, Vivocore Inc., InterVivo Solutions, and the University of Rochester and Massachusetts General Hospital.

Approximately 564,000 Canadians are estimated to be living with some form of dementia in 2016, according to data from the Alzheimer Society of Canada.