Optical coherence tomography in patients with Parkinson's disease

Background The changes in the different retinal layers in Parkinson's disease (PD) patients can be easily assessed using optical coherence tomography (OCT). Our aim was to evaluate retinal structural changes in patients with PD using OCT. Structural measurements of the retinal nerve fiber layer (RNFL), macular and ganglion cell complex (GCC) thicknesses were obtained using spectral domain optical coherence tomography. Disease severity was assessed using Unified Parkinson Disease Rating Scale (UPDRS). Results Retinal nerve fiber layer parameters, except for the superonasal and inferonasal quadrants, were significantly reduced in PD patients compared to controls. All macular parameters and GCC thickness were also reduced in PD patients compared to controls. Hoehn and Yahr (HY) staging was inversely correlated with all macular parameters, GCC and temporal RNFL thicknesses. UPDRS score showed a significant negative correlation with macular volume, inferior and nasal parafoveal thicknesses, nasal and temporal RNFL thicknesses and GCC thickness. The disease duration was inversely correlated with macular volume, inferior and temporal parafoveal thicknesses and GCC thickness. Using the multivariate linear regression analysis, the HY scale was a significant predictor for both the average GCC thickness and the macular volume. The sensitivity and specificity of average GCC thickness and macular volume to detect disease severity were 58.8%, 86.7%, 64.7% and 86.7%, respectively. Conclusion Parkinson's disease causes axonal damage in the RNFL along with retinal thinning that can be detected using SD-OCT. Patients with greater axonal damage tend to have longer duration of the disease and more severe PD symptoms.