Influence of age on the thickness of retinal nerve fiber layer in patients with mild-to-moderate stages of Parkinson’s disease: Case series

Parkinson’s disease, a neurodegenerative disease, involves motor and nonmotor components. Vision, a nonmotor component, has been studied by the analysis of the retinal layers by optical coherence tomography (OCT), and the main finding is the thinning of the retinal nerve fiber layer (RNFL). The aim of this study was to verify the influence of age on the thickness of retinal nerve fiber in patients with mild-to-moderate stages of Parkinson’s disease. Healthy individuals and patients with Parkinson’s disease were included in this prospective, cross-sectional, and observational study. The patients were recruited according to the clinical criteria from the neurology clinic of two major hospitals, with the description of the Hoehn and Yahr scale score. Healthy subjects were recruited from the general clinic and hospital staff. A comprehensive ophthalmic examination was performed previously on the spectral-domain OCT. There was a significant effect of age in the thickness of the RNFL in patients with Parkinson’s disease, in the right eye in the lower quadrant (P = 0.026) and in the left eye in the upper (P = 0.029) and temporal (P = 0.037) quadrants, as well in the control group in the upper (P = 0.003) and lower quadrant (P = 0.024). This case series could demonstrate that in mild-to-moderate stages of the Hoehn and Yahr Scale, there is an asymmetric correlation between aging and the decrease in superior, inferior, and temporal RNFL between the eyes of patients with Parkinson’s disease, and this finding precedes the decrease in visual acuity.