Optical coherence tomography and electrophysiology to evaluate Parkinson disease severity

Purpose To evaluate correlations between visual evoked potentials (VEP), pattern electroretinogram (PERG), and macular and retinal nerve fiber layer (RNFL) thickness measured by optical coherence tomography (OCT) and the severity of Parkinson disease (PD). Methods Forty-six patients diagnosed with PD were enrolled in this study and underwent VEP, PERG, and Cirrus and Spectralis OCT measurements of macular and RNFL thicknesses, and evaluation of PD severity using the Hoehn & Yahr scale to measure PD symptom progression, the Schwab and England Activities of Daily Living Scale (SE-ADL) to evaluate patient quality of life (QOL), and disease duration. Logistical regression was performed to analyze which measures, if any, could predict PD symptom progression or effect on QOL. Results Visual functional parameters (best corrected visual acuity, mean deviation of visual field, PERG P50 and N95 component amplitude, and PERG P50 component latency) and structural parameters (Cirrus and Spectralis OCT measurements of RNFL and retinal thickness) were decreased in PD patients compared with healthy controls. OCT measurements were significantly negatively correlated with the Hoehn & Yahr scale, and significantly postively correlated with the SE-ADL scale. Based on logistical regression analysis, fovea thickness provided by Cirrus OCT predicted PD severity, and QOL and amplitude of the PERG N95 component predicted a lower SE-ADL score. Conclusion Patients with greater damage in the RPE or in the ganglion cells tend to have a lower QOL and more severe PD symptoms. Foveal thicknesses and the PERG N95 component provide good biomarkers for predicting QOL and disease severity.