The Retinal Nerve Fiber Layer Thickness is Related to Severity of Parkinson’s Disease

Introduction: We investigated correlation between the retinal nerve fiber layer (RNFL) thickness and the severity of Parkinson's disease (PD). Methods: In this study, the RNFL thickness of 23 patients with Parkinson’s disease (PD) was compared to normal controls (NCs). PD severity was assessed by the MDS-UPDRS (movement disorder society Unified Parkinson Disease Rating Scale) rating scale thoroughly in all parts. RNFL is measured by Ocular Coherent tomography (OCT). Scatter plots were used to evaluate the relationship between disease severity and retinal thickness. Results: The findings of the study demonstrated that patients with PD had a significantly thinner average RNFL thickness compared with controls (P=0.035). Superior and inferior retinal quadrants were thinnest in PD compared with the healthy group (P=0.021 and P=0.045, respectively). The MDS-UPDRS had a significant reverse correlation with RNFL (r = -0.518, P=0.011) and its temporal quadrant (r = -0.594, P=0.003). Among all parts of MDS-UPDRS scale, Part III had the strongest correlation with OCT findings. Conclusion: A correlation was found between the severity of the disease and the thinning of RNFL. MDS-UPDRS Part III subscale had the strongest correlation with RNFL thickness. Temporal quadrant RNFL became thinner as Parkinson’s disease severity increased.