This study shows PD patients with depression exhibit pronounced oculomotor impairments—longer initiation times, slower smooth pursuit, and reduced saccade velocities—with average saccade velocity predicting depression (AUC 0.919) and negatively correlating with HAMD scores.

Identifies a noninvasive, objective biomarker (reduced saccade velocity) that could improve screening, stratification, and monitoring of depressive symptoms in PD—useful for clinical care and trial design—though it does not directly reveal therapeutic targets.

OBJECTIVE: To investigate whether oculomotor features can distinguish Parkinson's disease (PD) patients with depression (PD-D) from those without depression (PDND), and to assess their association with depression severity in PD. METHODS: Seventy-six PD patients were classified into PD-D and PDND groups based on clinical evaluation using the Hamilton Depression Rating Scale (HAMD). Eye movement data were collected using smooth pursuit, overlapping saccade, and anti-saccade tasks. Group differences in oculomotor parameters were analyzed. Receiver operating characteristic (ROC) curves were used to evaluate the diagnostic performance of oculomotor features. Partial correlation analysis examined relationships between oculomotor features and HAMD scores, controlling for relevant covariates. RESULTS: PD-D patients exhibited prolonged initiation time and slower pursuit velocity in the smooth pursuit task. In both the overlapping and anti-saccade tests, PD-D patients showed longer reaction times and reduced saccade velocities. Average saccade velocity in overlapping and anti-saccade tasks emerged as a significant predictor of depression, with an area under the curve (AUC) of 0.919. Saccade velocity was negatively correlated with HAMD scores (P < 0.01). CONCLUSIONS: Oculomotor abnormalities are more pronounced in PD patients with depression and are strongly correlated with depression severity. These abnormalities, particularly reduced saccade velocity, may serve as objective biomarkers for detecting depressive symptoms in PD. SIGNIFICANCE: Oculomotor features, as objective and non-invasive biomarkers, hold potential for clinical screening and monitoring of depression in PD patients, offering valuable tools for early detection and treatment planning.