Effects of levodopa on retina in Parkinson disease.

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.