Early Parkinson’s Diagnosis Could Be Possible Using Retinal Light Responses
Retinal responses to light could provide an early, non-invasive diagnostic tool for Parkinson’s disease.
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A study published in Neurobiology of Disease explores a potential new method for early detection of Parkinson's disease through retinal responses to light. This research, conducted by a team from Université Laval, reveals that the retina of individuals with Parkinson's disease responds differently to light stimuli compared to healthy individuals. The findings could open up possibilities for a simple, non-invasive diagnostic tool for Parkinson's disease.
Retina
The light-sensitive layer at the back of the eye that helps convert light into neural signals sent to the brain, allowing for vision.
Understanding parkinson's disease diagnosis
Parkinson's disease is traditionally diagnosed when patients present with motor symptoms, such as tremors, often after the disease has already caused significant neurodegeneration. This delayed diagnosis is problematic because by the time patients exhibit symptoms, the disease has progressed to a point where the damage is irreversible. Early diagnosis, therefore, is critical for effective intervention.
Professor Martin Lévesque, lead author of the study, explains that the retina, being a direct extension of the brain's central nervous system, could offer a non-invasive window into brain health. Detecting abnormal retinal responses to light could indicate an underlying neurological issue, such as Parkinson's disease.
Research Methodology
In this study, researchers tested the retinal responses of 20 people diagnosed with Parkinson's for less than 5 years. They used electrodes placed on the lower eyelid to measure the retina's reaction to various light flashes. These flashes varied in intensity, frequency and color. A control group of age-matched healthy individuals was also tested using the same procedure. The results revealed distinct differences in the retinal responses between the Parkinson’s group and the control group.
The researchers also conducted similar tests on transgenic mice. These mice were genetically engineered to overexpress a human protein associated with Parkinson's disease. Interestingly, even in the absence of visible motor symptoms, the mice showed abnormal retinal responses, mirroring the human data.
Transgenic mice
Mice that have been genetically modified to carry genes from other species, often used in research to study the effects of specific genes or diseases.
Implications of early diagnosis and future directions
Lévesque suggests that this retinal examination could be used as a screening tool for individuals aged 50 and older. Early detection through this simple test could allow for interventions aimed at preventing the degeneration of the brain’s neurons. Additionally, it could serve as a tool for monitoring disease progression and evaluating the effectiveness of treatments.
While Parkinson’s disease typically affects individuals over the age of 60, earlier diagnosis could significantly impact the approach to treatment and management. The researchers envision that this test could become a key part of clinical practice in the near future, offering a more proactive approach to treating Parkinson’s disease.
Reference: Soto Linan V, Rioux V, Peralta M, Dupré N, Hébert M, Lévesque M. Early detection of Parkinson’s disease: Retinal functional impairments as potential biomarkers. Neurobiol Dis. 2025;208:106872. doi: 10.1016/j.nbd.2025.106872
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