New research reveals a retinal light test may hold the key to detecting Parkinson’s disease long before motor symptoms appear.
Could your eyes reveal signs of Parkinson’s disease before symptoms appear? A new study says yes—and it might revolutionize early detection.
Researchers from Université Laval, publishing in the journal Neurobiology of Disease, have found that the retinas of people with Parkinson’s disease react to light in a distinctly different way than those of healthy individuals. This discovery could pave the way for a non-invasive, accessible screening method using routine eye exams.
Today, Parkinson’s is typically diagnosed only after noticeable motor symptoms, like tremors or stiffness, begin to disrupt daily life.
“By then, the disease has been present for several years and the affected neurons are already engaged in an irreversible degenerative process. That’s why it’s important to find biomarkers that detect Parkinson’s at an early stage of the disease,” explains study leader Martin Lévesque, professor at Université Laval’s Faculty of Medicine and researcher at CERVO Brain Research Centre in Québec City.
The Retina as a Window into the Brain
“The retina is a direct extension of the central nervous system and, consequently, offers a non-invasive way of exploring the brain”, continues the researcher. “An unusual response of the retina to light stimuli could be indicative of a pathology affecting the brain.”
To explore this avenue, his research team recruited 20 people who had been diagnosed with Parkinson’s for less than 5 years.
“We placed an electrode on each participant’s lower eyelid and recorded their retinal response to a series of flashes of different intensity, frequency, and color. We did the same with people of the same age, but in good health. The results we obtained for people with Parkinson’s had a distinct signature from those in the control group,” explains Professor Lévesque.
Animal Models Confirm Findings
The research team carried out similar tests in transgenic mice overexpressing a human protein associated with Parkinson’s disease.
“We used young mice in which no motor signs of the disease were yet observable. Once again, we obtained different responses in Parkinson’s model animals. This suggests that the functional manifestations of Parkinson’s could be detected at an early stage of the disease by retinal examination,” sums up Martin Lévesque.
Parkinson’s disease occurs most often in people over the age of 60.
“We could offer a functional retinal exam from the age of 50,” continues Lévesque. “By detecting the disease early, we could offer interventions that prevent the degeneration of the neurons involved in Parkinson’s. This approach could also be used to monitor the progression of the disease, as well as the effectiveness of interventions offered to patients.”
Reference: “Early detection of Parkinson’s disease: Retinal functional impairments as potential biomarkers” by Victoria Soto Linan, Véronique Rioux, Modesto Peralta, Nicolas Dupré, Marc Hébert and Martin Lévesque, 14 March 2025, Neurobiology of Disease.
DOI: 10.1016/j.nbd.2025.106872
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