This cross-sectional study found corneal epithelial thinning measured by AS-OCT correlates with dry eye severity and Hoehn & Yahr stage in Parkinson's patients.

Zonal corneal epithelial thickness mapping is a non-invasive biomarker candidate that could help disease staging and patient stratification in trials, but it offers limited direct mechanistic or therapeutic insight for Parkinson's drug discovery.

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.