Parkinson’s Disease

Parkinson’s disease is a progressive neurological disorder that affects both movement and many other aspects of health. While it is best known for its motor symptoms, such as tremors, muscle stiffness (rigidity), and slowness of movement (bradykinesia), it also causes a range of non-motor symptoms, such as cognitive impairments, depression, and sleep disturbances. Currently, Parkinson’s disease is typically diagnosed only after obvious symptoms appear, at which point a significant brain damage has already occurred. This delay in diagnosis makes early intervention difficult, limiting the effectiveness of treatments.

Neurology & Sleep Centre | Manvir Bhatia 

A recent study by Linan et al. from Université Laval suggests that subtle changes in how the eye responds to light might serve as early signs of Parkinson’s disease, long before symptoms emerge.

Because the eye is directly connected to the brain, the retina offers a unique opportunity to detect brain-related diseases. This research team used a non-invasive tool called an electroretinogram (ERG), which records electrical signals produced by the retina in response to flashes of light. They performed this test in both patients with early-onset Parkinson’s disease and mice genetically engineered to model the early stages of the condition. They found that even at these early stages, both groups showed altered retinal responses in certain parts of the retina compared to healthy controls. 

Wikimedia commons | QDAVIS

Interestingly, the researchers also found abnormal buildup of alpha-synuclein—a protein that clumps in the brains of people with Parkinson’s disease—in the retinas of the mice. This is a significant discovery because it shows that the same pathological process occurring in the brain may also be happening in the eye. This strengthens the idea that the retina could reflect early signs of brain disease.

According to the authors, this is the earliest recorded instance of ERG anomalies in people diagnosed with Parkinson’s disease, and it could pave the way for new diagnostic tools. While more research is needed to define a more consistent and reliable ERG signature, the study marks a major step forward in the search for early detection tools. 

References

Admin. (2025, June 7). What is parkinson’s disease: Parkinson’s disease treatment. Neurology & Sleep Centre. https://neurologysleepcentre.com/blog/what-is-parkinsons-disease/ 

Haseltine, W. A. (2024, February 20). What is that new machine your eye doctor is using and why: Electroretinography. Forbes. https://www.forbes.com/sites/williamhaseltine/2024/02/19/what-is-that-new-machine-your-eye-doctor-is-using-and-why-electroretinography/ 

Linan, V. S., Rioux, V., Peralta, M., Dupré, N., Hébert, M., & Lévesque, M. (2025). Early detection of parkinson’s disease: Retinal functional impairments as potential biomarkers. Neurobiology of Disease, 208, 106872.