Aims To determine whether there is an association between retinal thinning and functional rating scales in patients with Parkinson's disease (PD). Materials and methods Patients with PD (n=153) and controls (n=242) underwent evaluations of the macula and retinal nerve fibre layer (RNFL) using two new-generation Fourier domain optical coherence tomography (OCT) devices (Cirrus, Carl Zeiss Meditec, Dublin, California, USA; Spectralis, Heidelberg Engineering, Heidelberg, Germany). PD severity was assessed using the Schwab-England Activities of Daily Living scale, the Unified Parkinson Disease Rating Scale, the Hoehn and Yahr (HY) scale. Retinal and RNFL thicknesses were compared between patients and controls. Correlations between structural parameters and the scores of the neurologic scales were evaluated. Results RNFL parameters were significantly reduced in patients with PD, especially when using the Spectralis OCT device. All macular parameters, except for foveal thickness, differed significantly between controls and patients with PD (p<0.001). HY scores were significantly and inversely correlated with all macular parameters when measured with the Spectralis OCT device (p<0.05) and with RNFL thickness when measured with the Cirrus OCT device (nasal quadrant, sectors 2 and 5). Conclusions The neurodegeneration caused by PD can be detected using Fourier domain OCT. RNFL and macular thicknesses correlate with PD 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 PD patients and 33 age and sex-matched healthy controls were enrolled, and underwent VEP, PERG, and OCT measurements of macular and RNFL thicknesses, and evaluation of PD severity using the Hoehn and 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 positive (P) component at 50 ms -P50- and negative (N) component at 95 ms -N95- component amplitude, and PERG P50 component latency) and structural parameters (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 and Yahr scale, and significantly positively correlated with the SE-ADL scale. Based on logistical regression analysis, fovea thickness provided by OCT equipment predicted PD severity, and QOL and amplitude of the PERG N95 component predicted a lower SE-ADL score. Conclusions. Patients with greater damage in the RNFL tend to have lower QOL and more severe PD symptoms. Foveal thicknesses and the PERG N95 component provide good biomarkers for predicting QOL and disease severity.

Neurodegenerative diseases present a current challenge for accurate diagnosis and for providing precise prognostic information. Developing imaging biomarkers for multiple sclerosis (MS), Parkinson disease (PD), and Alzheimer’s disease (AD) will improve the clinical management of these patients and may be useful for monitoring treatment effectiveness. Recent research using optical coherence tomography (OCT) has demonstrated that parameters provided by this technology may be used as potential biomarkers for MS, PD, and AD. Retinal thinning has been observed in these patients and new segmentation software for the analysis of the different retinal layers may provide accurate information on disease progression and prognosis. In this review we analyze the application of retinal evaluation using OCT technology to provide better understanding of the possible role of the retinal layers thickness as biomarker for the detection of these neurodegenerative pathologies. Current OCT analysis of the retinal nerve fiber layer and, specially, the ganglion cell layer thickness may be considered as a good biomarker for disease diagnosis, severity, and progression.