Corneal epithelial thickness can reflect the stage of Parkinson’s disease and the severity of dry eye

Purpose To systematically analyze corneal epithelial thickness (CET) distribution in Parkinson’s disease (PD) using anterior segment optical coherence tomography (AS-OCT) and investigate its correlation with disease stage and dry eye severity. Methods This cross-sectional study enrolled 60 PD patients (120 eyes) and 29 age- and sex-matched healthy controls (58 eyes). The accessed parameters included dry eye disease (DED) metrics, such as the Ocular Surface Disease Index (OSDI), Schirmer I test (sIt), tear breakup time (BUT), corneal fluorescein staining (CFS), corneal sensitivity, and zonal CET measured by AS-OCT in central 2-mm, 5-mm, and 6-mm zones. Baseline PD characteristics included disease duration, levodopa equivalent daily dose (LEDD), Hoehn and Yahr (H-Y) stage, Movement Disorder Society Unified Parkinsond dPisease Rating Scale (MDS-UPDRS Part III), and Montreal Cognitive Assessment (MoCA). Results PD patients showed significantly higher OSDI and CFS ( p < 0.001), and lower sIt, BUT, and CET ( p < 0.001). CET was significantly thinner in temporal, superior, and nasal quadrants of the 6-mm zone ( p < 0.05). Temporal 6-mm CET was positively correlated with BUT ( p = 0.024). With advancing H-Y stage, peripheral CET progressively thinned, while OSDI increased and BUT and sIt decreased, indicating worsening DED. Conclusion This study demonstrates, for the first time, that CET correlates with both dry eye severity and H-Y stage in PD. AS-OCT-based CET mapping may serve as a non-invasive biomarker for early neurodegeneration detection and guide ocular surface management.