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Purpose To demonstrate axonal loss in the retinal nerve fiber layer (RNFL) of patients with Parkinson's disease (PD) and to evaluate the ability of Fourier-domain optical coherence tomography (OCT) to detect RNFL degeneration and retinal thinning in these patients. Methods PD patients (n ¼ 100) and healthy subjects (n ¼ 100) were included in the study and underwent visual acuity, color vision, and OCT examinations using two nextgeneration Fourier-domain devices (Spectralis and Cirrus). Differences in the RNFL thicknesses were compared between patients and controls. Results RNFL thicknesses were significantly reduced in PD patients compared with healthy subjects, especially those obtained using the Spectralis OCT, in the inferotemporal quadrant (155.6 ± 16.5 lm in healthy eyes vs 142.1 ± 24.9 lm in patients, P ¼ 0.040) and in the superotemporal quadrant (142.6±20.9 lm in healthy eyes vs 132.77±18.6 lm in PD patients, P ¼ 0.046). Significant differences were observed between controls and patients in relation to mean macular thickness (P ¼ 0.031), foveal thickness (P ¼ 0.030), and inferior outer thickness (P ¼ 0.019). Conclusion PD is associated with RNFL loss and retinal thinning, which is detectable by Fourier-domain OCT measurements.

ABSTRACT.Purpose: To evaluate the thickness of the 10 retinal layers of patients with Alzheimer's disease (AD) using a new segmentation technology of the Spectralis optical coherence tomography (OCT) and to determine whether the thickness of specific layers predicts neurodegeneration or AD severity. Methods: Patients with AD (n = 150) and age-matched healthy controls (n = 75) were analysed using the segmentation application prototype to automatically segment all retinal layers in a macular scan. Thicknesses of each layer were compared between patients with AD and controls, and between patients with disease durations of less than or at least 3 years. Associations between retinal layer thicknesses, disease duration and AD severity were evaluated. Results: Patients with AD had reduced thickness in the retinal nerve fibre, ganglion cell, inner plexiform and outer nuclear layers (p < 0.05). The inner retinal layers were more affected in patients with long disease duration. Ganglion cell and retinal nerve fibre layer thicknesses were inversely correlated with AD duration and severity. Ganglion cell and inner plexiform layers thicknesses were predictive of axonal damage. Conclusions: The segmentation application revealed ganglion cell and retinal layer atrophy in patients with AD compared with controls, especially in the inner layers of patients with long disease duration. Ganglion cell layer reduction was associated with increased axonal damage and may predict greater disease severity.

The neurodegeneration caused by PD can be detected using Fourier domain OCT. RNFL and macular thicknesses correlate with PD severity.