Good balance and good eyesight are really important for performing different tasks and getting around. People with Parkinson’s disease (PD) often have trouble with both balance and moving their eyes.
A new study examined how saccadic eye movements affect body sway in people with PD while standing in two positions: side-by-side and tandem (one foot in front of the other).
Researchers at São Paulo State University (UNESP) in Brazil and the University of Lille in France found that rapid side-to-side eye movements can help stabilize posture, avoid falls, and maintain balance for people with Parkinson’s disease, just as they can for healthy people.
The study involved ten people with Parkinson’s disease and eleven healthy individuals over 60 years old. Participants were tested while standing still in two positions: side-by-side and tandem (one foot in front of the other). They made quick eye movements (horizontal and vertical) or focused on a fixed target.
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The results showed that horizontal eye movements helped reduce body sway for both groups, regardless of their foot position. In contrast, vertical eye movements were linked to increased body sway, specifically in people with Parkinson’s disease.
Fabio Barbieri, the first author of the article and head of UNESP’s Human Movement Research Laboratory (MOVI-LAB), said, “We didn’t expect people with Parkinson’s to be capable of combining these two movements. Our findings furnish new knowledge of the disease and of its motor and cognitive consequences.”
At the start of the study, researchers believed that eye movements wouldn’t help people with Parkinson’s maintain stability and avoid falls due to their balance and eye control difficulties. Individuals with Parkinson’s often have slow blinking and struggle to take in visual information from their surroundings.
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The study found that horizontal eye movements helped improve stability, while vertical movements worsened body sway in Parkinson’s patients. Vertical movements are beneficial for younger adults, but they don’t help with balance for older adults. This is partly because vertical movements are harder and involve less eye rotation, making it difficult to connect visual information with body control.
Sérgio Tosi Rodrigues, the lead author, has researched postural stability and eye movements across various groups, including healthy and older adults, diabetics, and those with multiple sclerosis. Previous studies suggest that the body’s balance system relies on both visual information from the eyes and signals from the muscles that move the eyes, which work together to help reduce body sway.
Tosi Rodrigues said, “Besides limitations due to a disease, such as Parkinson’s, control of gaze and posture seems to vary with age. Generally speaking, the natural aging process leads to a deterioration of motor control and visual perception, among other alterations. Visual functions perform less well in older than younger people, for example, potentially making older people more susceptible to falls.”
Barbieri states, “Combining static balance with vertical saccadic eye movements may be difficult for Parkinson’s patients, increasing body sway as a result.”
Journal Reference:
- Fabio Augusto Barbieri, Paula Favaro Polastri et al. People with Parkinson’s Disease Are Able to Couple Eye Movements and Postural Sway to Improve Stability. Biomechanics. DOI: 10.3390/biomechanics4030032
