Ganglion cell-ınner plexiform layer thickness in patients with parkinson disease and association with disease severity and duration

Abstract

Background: To evaluate the average, minimum, and 6-sectoral macular ganglion cell-inner plexiform layer (GCIPL) thickness measured by spectral domain optical coherence tomography (SD-OCT) in patients with Parkinson disease (PD), as well as average and 4-sectoral retinal nerve fiber layer (RNFL) thickness and to determine whether thickness parameters are correlated to disease severity and duration. Methods: Patients with PD (n = 54) and age-matched healthy controls (n = 54) were prospectively examined with SD-OCT. Randomly selected eyes of all subjects were included. The average, minimum, and 6-sectoral (superior, superotemporal, superonasal, inferonasal, inferior, and inferotemporal) GC-IPL thickness values were analyzed. Average and 4-sectoral (inferior, superior, temporal, and nasal) peripapillary RNFL thicknesses were also evaluated. Each parameter was compared between patients with PD and age-matched healthy controls. PD severity was quantified with the Hoehn and Yahr (HY) scale. A correlation analysis was performed to evaluate the association between SD-OCT measurements and the duration and severity of PD. Results: The mean age of patients with PD and age-matched healthy controls was 66.62 +/- 8.71 years and 66.68 +/- 7.85 years, respectively. Disease duration ranged from 1 to 15 years with a mean of 5.12 years. The mean PD severity, according to the HY scale, was 2.26 (range, 1-5). SD-OCT measurements revealed significant differences in inferior and temporal peripapillary RNFL values between groups (P = 0.018 and P = 0.031, respectively). All GC-IPL thickness parameters were statistically lower in the patients with PD when compared with the healthy controls (P, 0.001). PD duration was not correlated to any of the RNFL thicknesses, but PD severity was correlated inversely only with inferior peripapillary RNFL thickness (P = 0.006). Average, inferior (P = 0.011), inferotemporal (P = 0.007), and superotemporal (P = 0.007) GC-IPL thicknesses were correlated inversely with both PD severity and duration. Conclusions: Retinal dopaminergic neurodegeneration in patients with PD can be detected with macular GC-IPL thickness measurements. Macular GC-IPL thickness was correlated with PD severity and duration. It may be used to follow disease progression and efficacy of the neuroprotective treatment in patients with PD.