Vision, visuo-cognition and postural control in Parkinson's disease: An associative pilot study

Introduction: Impaired postural control (PC) is common in patients with Parkinson's disease (PD) and is a major contributor to falls, with significant consequences. Mechanisms underpinning PC are complex and include motor and non-motor features. Research has focused predominantly on motor and sensory inputs. Vision and visuo-cognitive function are also integral to PC but have largely been ignored to date. The aim of this observational cross-sectional pilot study was to explore the relationship of vision and visuo-cognition with PC in PD. Methods: Twelve people with PD and ten age-matched healthy controls (HC) underwent detailed assessments for vision, visuo-cognition and postural control. Vision assessments included visual acuity and contrast sensitivity. Visuo-cognition was measured by visuo-perception (object identification), visuo-construction (ability to copy a figure) and visuo-spatial ability (judge distances and location of object within environment). PC was measured by an accelerometer for a range of outcomes during a 2-min static stance. Spearman's correlations identified significant associations. Results: Contrast sensitivity, visuo-spatial ability and postural control (ellipsis) were significantly impaired in PD (p = 0.017; p = 0.001; and p = 0.017, respectively). For PD only, significant correlations were found for higher visuo-spatial function and larger ellipsis (r = 0.64; p = 0.024) and impaired attention and reduced visuo-spatial function (r = -0.62; p = 0.028). Conclusions: Visuo-spatial ability is associated with PC deficit in PD, but in an unexpected direction. This suggests a non-linear pattern of response. Further research is required to examine this novel and important finding.