Movement and successful completion of tasks depends on coordination between postural control and the visual system, but in conditions such as Parkinson’s disease, these abilities become compromised. Recent research explored how horizontal and vertical saccadic eye movements influenced body sway in side-by-side and tandem stances for people with Parkinson’s disease compared to healthy individuals.
The study included 10 Parkinson’s disease (PD) patients and 11 healthy individuals, and both groups performed fixation, horizontal, and vertical saccadic eye movements. Both PD patients and controls showed reduced anterior–posterior body sway during horizontal saccadic movements compared to fixation, regardless of stance. However, vertical saccadic movements increased sway area in PD patients. PD patients also showed significantly higher body sway in the tandem stance than in the side-by-side stance.
Regarding eye movement, PD patients exhibited more frequent and shorter fixations across all conditions, indicating less stable gaze control. Vertical saccadic movements were especially challenging and affected stability and gaze behavior more than horizontal movements.
“People with PD display larger body sway magnitude, higher body sway acceleration and velocity, and lower complexity and adaptability in postural control function while standing upright compared to age-matched neurologically healthy controls,” the investigators wrote in their article, recently published in Biomechanics. “In addition, their limits of stability are reduced due to a disruption of the precisely coordinated execution of agonist and antagonist muscles.”
They further described that while “individuals with PD particularly rely on visual information to compensate for deficits in postural sway control,” PD patients may also experience “a decreased range of eye movements and prolonged saccadic latency”, as well as “hypometria during the execution of voluntary saccades…and impairment of antisaccade latencies, which is an indirect marker of impaired anticipatory postural adjustments.”
The researchers explained that the pedunculopontine nucleus area of the brain may explain some of the visual-motor dysfunction seen in PD patients, but concluded that extension studies of late-stage PD would be relevant to further validate their findings, which were only applicable for initial and moderate stages.
This research suggests that horizontal eye movement exercises could help counter postural control impairments for PD patients, especially in challenging stance positions.
The authors declared no conflicts of interest.
