Study reveals the role of eye movements in Parkinson's disease

Ten individuals diagnosed with Parkinson's and 11 neurologically healthy individuals participated in the study. All participants were over 60 and were submitted to tests that involved standing still and trying to maintain balance with their feet side by side and parallel, or one foot in front of the other (tandem stance), while making horizontal or vertical saccadic eye movements, or gazing steadily at a fixed target.

Horizontal saccadic eye movements rather than gaze fixation correlated with significantly reduced body sway for both the healthy participants and those with Parkinson's, regardless of the position of the feet (side-by-side or tandem), while vertical saccadic eye movements correlated with increased body sway for the latter group.

Unexpected benefit

When the researchers began the study, they thought eye movements could not help Parkinson's patients maintain stability and avoid falls.

Tosi Rodrigues has conducted studies on postural stability and saccadic eye movements in different populations, such as healthy young and older adults, diabetics, and multiple sclerosis as well as Parkinson's patients.

The results of previous studies suggest the postural control system receives both visual information from images projected on the retina and inputs from the muscles that move the eyes, which help reduce body sway.

"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," Tosi Rodrigues said.

According to Barbieri, "combining static balance with vertical saccadic eye movements may be difficult for Parkinson's patients, increasing body sway as a result".

In healthy individuals, vertical and horizontal saccadic eye movements benefited postural stabilization more than fixed gaze. "This happens because postural control is backgrounded. To try to simplify what's complex, there's a change in attention. The subject shifts attention from posture to focus on eye movement, requiring more caution from the brain in order to control posture and stability so as to avoid a fall," Barbieri said.

Source:Journal reference:

Barbieri, F. A., et al. (2024). People with Parkinson’s Disease Are Able to Couple Eye Movements and Postural Sway to Improve Stability. Biomechanics. doi.org/10.3390/biomechanics4030032.