title: Ganglion cell-inner 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 (GC-IPL) 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.
authors.affiliation: Departments of Ophthalmology (ESS, AY, GS, SSE) and Neurology (RK), Balikesir University Faculty of Medicine, Balikesir, Turkey.
authors.forename: Esin S
authors.initials: ES
authors.lastname: Sari
authors.forename: Rabia
authors.initials: R
authors.lastname: Koc
authors.forename: Alper
authors.initials: A
authors.lastname: Yazici
authors.forename: Gözde
authors.initials: G
authors.lastname: Sahin
authors.forename: Sitki S
authors.initials: SS
authors.lastname: Ermis
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000473:pathology*; D010300:Parkinson Disease / Q000473:pathology*; D012165:Retinal Ganglion Cells / Q000473:pathology*; D012720:Severity of Illness Index; D041623:Tomography, Optical Coherence; D014795:Visual Pathways / Q000473:pathology