Could a Simple Eye Test Predict Cognitive Decline in Parkinson’s Patients?

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A recent study by University College London researchers found that Parkinson’s patients with visual dysfunction showed worse cognition and may be at a higher risk of developing dementia.

While Parkinson’s disease is traditionally thought of as a movement disorder that mainly affects motor functions, emerging evidence suggests that it can also affect cognition. In fact, over 50% of people with Parkinson’s disease will develop dementia within 10 years since their diagnosis. But, being a highly varied and heterogenous disease, it is difficult to identify which patients will go on to develop dementia or cognitive impairment.

This study found that visual dysfunction may help predict which Parkinson’s patients will develop dementia. They recruited 101 subjects, 77 of which were diagnosed with Parkinson’s. Each participant then completed two visual examinations, including the biological motion test:

Biological Motion Test was used to examine patients’ visual abilities


According to their combined result in both visual tests, the participants were then classified as either low-visual-performers or high-visual-performers.

After 18 months, the participants underwent further examinations that tested their cognitive abilities. Interestingly, the researchers found that Parkinson’s patients that were previously classified as low-visual-performers, achieved lower scores on their cognitive tests, compared to patients who were high-visual performers. This may suggest that Parkinson’s patients with visual dysfunction are more likely to have worse cognitive abilities and to develop mild cognitive impairment and dementia. Furthermore, the study found that Parkinson’s patients with lower visual abilities that went on to develop dementia, also had more damage in their white matter (or simply-put, the wiring of the brain), specifically in the regions responsible for visual and memory.

While additional long-term studies are needed to confirm this relationship between visual dysfunction and cognitive decline, these results help us better understand the mechanisms of cognitive decline in Parkinson’s disease. The results could also be valuable for future clinical research, as a simple vision test may be able to predict which Parkinson’s patients will develop dementia, as early as 18 months prior to cognitive decline. Thereby, by identifying at-risk patients early, they could be recruited for clinical trials and potentially aid in the development of new Parkinson’s drugs.

Featured image: pexels

Featured study: Zarkali, A., McColgan, P., Leyland, L. A., Lees, A. J., & Weil, R. S. (2021). Visual Dysfunction Predicts Cognitive Impairment and White Matter Degeneration in Parkinson’s Disease. Movement disorders : official journal of the Movement Disorder Society, 10.1002/mds.28477.

Edited by Cyrus Rohani-Shukla

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