Background: Emerging evidence suggests that ocular and radiological parameters may serve as early indicators of neurological decline in Parkinson's disease (PD). This study aims to compare specific eye-related measurements between individuals with PD and healthy controls and evaluate the correlation between ocular measurements and clinical as well as radiological parameters.

Methods: This case-control study was conducted between February 2022 and September 2023. The study included 22 PD patients and 20 healthy controls. Neurological and ophthalmological evaluations were performed using optical coherence tomography to assess retinal structures. Additionally, magnetic resonance imaging with diffusion tensor imaging was used to measure white matter integrity.

Results: The study enrolled 42 participants, with a predominance of males. Disease severity and cognitive functions were assessed and indicated considerable impairment among PD patients. Ocular and retinal parameters showed differences in retinal nerve fiber layer thickness and choroidal thickness. MRI metrics showed significant reductions in fractional anisotropy and increases in mean diffusivity in several brain regions of PD patients, indicating white matter degeneration. Correlation analyses revealed significant associations between ocular parameters as well as white matter integrity and cognitive impairment.

Conclusion: Our study suggests that degenerative processes in PD extend beyond the central nervous system to involve the eye, with significant retinal neurodegeneration and increased axonal damage compared to healthy controls. Comprehensive assessments combining ocular, neurological, and radiological parameters could improve the understanding and management of PD.

Keywords: Parkinson's Disease, Cognition, Neurodegeneration, Radiology, ophthalmology