Correlation between non-motor symptoms and eye movements in Parkinson's disease patients.

Introduction: Parkinson's disease (PD) presents with a variety of non-motor symptoms such as sleep disorders, hyposmia, pain, cognitive dysfunction, neuropsychiatric and autonomic symptoms. One of the most neglected motor symptoms is the impairment of eye movements, which occurs in 75% of PD patients. The aim of our study was to investigate the relationship between the severity of non-motor symptoms and the impairment of different types of eye movements.

Methods: We conducted a cross-sectional study with idiopathic PD patients in which non-motor symptoms were assessed using standardised scales. The impairment of smooth pursuit, saccades, antisaccades and visually-guided saccades was evaluated with eye-tracker analysis, using battery of tests.

Results: The mean age of our subjects was 65.06 (± 9.135; 43-80) years with a median disease duration of 4 (2-7) years. The duration of PD correlated positively with visually-guided memory saccades. We found moderate positive correlations between scales for sleep quality, depression, anxiety, and nonmotor experiences of daily living (PDSS-2, RBDSQ, BAI, BDI-II, MDS-UPDRS I) with deviation of fast smooth pursuit movements and latency of saccades and antisaccades. Number of correct answers in different trials testing visually-guided memory saccades were most strongly negatively correlated with scales assessing depression, sleep quality and cognitive functions (MoCA).

Conclusion: Different types of eye movement parameters correlate with scales assessing non-motor symptoms, possibly caused by the same pathophysiological mechanism in PD. Further research that addresses these challenges and focuses on the relationship between eye movements and specific non-motor symptoms in PD could provide valuable insights into the comprehensive management of this complex disease.