Choroidal thickness in the eyes of Parkinson's disease patients measured using optical coherence tomography: A systematic review and meta-analysis

Background: Parkinson's disease (PD) presents a complex etiology involving genetics and environmental factors. Non-motor symptoms often precede motor manifestations. Dopaminergic neuron degeneration, oxidative stress, and vascular changes characterize PD. Retinal changes are studied as potential biomarkers, yet choroidal involvement remains unclear. This review aims to clarify choroidal thickness's role in PD progression for diagnostic advancements. Methods: We examined PubMed, Scopus, and Embase databases. Depending on the heterogeneity, an appropriate model was used for the meta-analysis. Additionally, meta-regression, publication bias, subgroup analyses, and quality evaluation were carried out. Results: We evaluated twelve studies involving 442 PD patients and 608 healthy controls. This study found insignificant differences in choroidal thickness between PD patients and healthy controls. Conclusion: Choroidal thickness is influenced by age, axial length, and intraocular pressure, with PD potentially impacting thickness through neurodegenerative mechanisms. However, inconsistencies exist in the findings, warranting further investigation. Future studies should explore the impact of disease severity, medication effects, and other confounding variables on choroidal thickness in PD patients. Additionally, advanced imaging modalities like optical coherence tomography angiography (OCTA) may provide more comprehensive evaluations of choroidal vascular changes in PD.