Oculomotor and clinical correlates with impaired optokinetic nystagmus in Parkinson’s disease

Abnormalities in eye movement are promising indicators of Parkinson’s disease (PD); however, the role of optokinetic nystagmus (OKN) in PD remains poorly understood. In this study, we addressed this gap by investigating the performance of OKN in individuals with PD and its correlation with other ocular and clinical characteristics. A cohort comprising 251 patients with PD and 46 age-matched healthy controls (HCs) underwent comprehensive oculomotor assessments.

These assessments included the recording of OKN, visually guided saccades, and smooth pursuit eye movements (SPEM) across three motion frequencies along the horizontal axis. Patients with PD were clinically evaluated using a series of scales for both motor and non-motor symptoms. The associations between key oculomotor parameters and clinical phenotypes in patients with PD were investigated.

Compared to HCs, patients with PD presented significantly reduced OKN gain. The OKN gain was strongly correlated with saccade latency and SPEM gain across all tested frequencies but not with saccade accuracy. Among all eye movement parameters, OKN gain and saccade latency were associated primarily with the Freezing of Gait Questionnaire (FOG-Q) score and cognitive score.

After controlling for confounding variables, however, OKN gain, rather than saccade latency, was independently associated with the occurrence of FOG in patients with PD. Next, we developed a predictive model, incorporating factors such as age, OKN gain, scores from the MDS-Unified Parkinson’s Disease Rating Scale Part III (MDS-UPDRS-III), the Chinese version of the Montreal Cognitive Assessment-Basic (MoCA-BC), and the presence of the wearing-off phenomenon. This model had an accuracy rate of 80.4% in predicting the risk of FOG.

We found that OKN is impaired and associated with saccade and SPEM performance in PD patients. Reduced optokinetic gain may increase the likelihood of the FOG phenotype in PD patients. We sincerely thank all the patients and volunteers for their invaluable participation and support in this study.

This work was supported by the Project of Biobank from Shanghai Ninth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine (Grant No. YBKB202120), which provided funding for data collection and sample storage; Clinical Cohort Shanghai (Grant No. SHDC2025CCS043), which supported the establishment and maintenance of the clinical database; the Fundamental Research Program Funding of Shanghai Ninth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine (Grant No.