Analysis of the retinal nerve fiber and ganglion cell - Inner plexiform layer by optical coherence tomography in Parkinson's patients

Aim: To measure and evaluate the thickness of the retinal nerve fiber layer (RNFL) and ganglion cell inner plexiform layer (GC-IPL) in patients with Parkinson's disease using optical coherence tomography (OCT). Methods: 58 eyes of 30 patients with 'Parkinson's disease and 60 eyes of 30 healthy individuals were enrolled to this study according to defined criteria. RNFL thickness, central macular thickness (CMT) and ganglion cell-inner plexiform layer (GC-IPL) thickness were measured in these groups. The Parkinson's patient group was also subjected to Unified Parkinson's Disease Rating Scale (UPDRS) and Mini Mental Status Exam (MMSE). Results: No difference was found between the two groups with respect to age, sex and the best corrected visual acuity (BCVA). Mean, superior, and inferior quadrant RNFL values in the Parkinson's patients were found statistically significantly lower than those in the control group (P < 0.001, P < 0.049, P < 0.001, respectively). While CMT was statistically similar between the groups, GC-IPL thickness was statistically significantly lower in Parkinson's patients (p = 0.028). There was no significant correlation between the duration of Parkinson's disease and RNFL thickness. While there was not any correlation between UPDRS total and motor scores and superior and temporal quadrant RNFL thicknesses, a significant negative correlation was established between RNFL nasal, inferior quadrant and RNFL mean thicknesses (P = 0.022; P = 0.035; P = 0.002, respectively). A significant positive correlation was found between MMSE and nasal and mean RNFL thicknesses (P = 0.046; P = 0.019, respectively). Conclusion: RNFL and GC-IPL thicknesses were found lower in Parkinson's patients. These parameters may be useful to evaluate neurodegeneration and to monitorize neuroprotective therapies. (C) 2016 Elsevier Ltd. All rights reserved.