Retinal Changes in Parkinson's Disease: A Longitudinal Follow-up Study

Background: There is definite evidence for the involvement of retina in Parkinson's disease (PD). However, a specific pattern has not been clear due to the cross-sectional nature of the majority of the previous studies. Objective: The aim of this work was to study the pattern of changes in the retinal layers in patients with PD on longitudinal follow-up. Materials and Methods: Twelve patients with PD (23 eyes) were evaluated at baseline with complete history, clinical examination, Unified Parkinson's Disease Rating Scale (UPDRS) motor part, visual acuity, and retinal imaging with spectral-domain Optical Coherence Tomography. After a mean duration of 3.7 +/- 0.46 years, patients were re-evaluated. Results: The Central Macular Thickness (CMT) of the right eye was found to be significantly thicker during the follow-up (P = 0.002). The outer retinal layer in the temporal quadrant at 0.5 centimeters from the fovea of the left eye was found to be significantly thinner (P = 0.001). Conclusion: The serial evaluation of the retinal layers in patients with PD suggests a progressive loss of thickness of the outer retinal layer. The involvement of non-dopaminergic mechanisms, especially glutamatergic pathways, may be responsible for these changes.