Effects of Levodopa on Retina in Parkinson Disease

Abstract

Purpose To evaluate the effects of levodopa on retina, we assessed retina with optical coherence tomography (OCT) in Parkinson disease (PD). Methods Thirty-five patients with PD (17 with levodopa monotherapy, 18 untreated) and 11 healthy controls were included in this cross-sectional study. Unified Parkinson's Disease Rating Scale (UPDRS) and Hoehn & Yahr (H&Y) staging scale were used for the evaluation of disease severity. All retinal scans were performed using OCT. Results Total UPDRS and motor subscores were lower in untreated patients compared to patients with treated PD (p = 0.013, p = 0.033, respectively). There was no significant difference in the range of H&Y stages between the untreated and treated PD groups (p = 0.342). The average retinal nerve fiber layer thickness of the untreated (106.76 ± 10.55 μm) and treated (104.62 ± 8.23 μm) patients with PD were significantly thinner than those of controls (115.60 ± 9.11 μm) (p<0.005). However, there was no significant difference between the untreated and patients with treated PD (p = 0.780). No significant difference in mean values of average thickness of ganglion cell complex layer was observed among controls, patients with untreated PD, and patients with treated PD (p = 0.304). Conclusions Although the disease in patients with treated PD was more severe than in the untreated group, no significant difference in the thickness of retina was found between the 2 groups. Therefore, we thought that levodopa might have a protective effect on retina in patients with PD.