title: Nerve fiber layer measurement using scanning laser polarimetry with fixed corneal compensator in normal cynomolgus monkey eyes.
abstract: OBJECTIVE
  The purpose of this study was to examine retinal nerve fiber layer thickness in normal cynomolgus monkeys using a scanning laser polarimeter with a fixed corneal compensator (GDx FCC), and to clarify the reproducibility and symmetries (right-left differences) between both eyes for the GDx parameters.
  
  
  METHODS
  GDx parameters were measured in 36 normal eyes of 18 cynomolgus monkeys aged 4.0-5.5 years. The retardation values (thickness parameters) at peripapillary and macular areas obtained from the GDx FCC were measured and calculated thickness, ratio, and modulation parameters in the superior and inferior quadrants. Mean and standard deviation (SD), coefficient of variation (CV), and binocular differences were obtained for each parameter from three independent measurements made during a 1-week period. Correlation between both eyes in macular retardation and baseline values, which indicated the combined minimum retardation values for the nasal and temporal quadrants, and between macular retardation and baseline values were analyzed.
  
  
  RESULTS
  The intraocular pressure values (mean +/- SD, n = 18) obtained for the right and left eyes were 20.7 +/- 3.8 and 20.0 +/- 3.2 mm Hg, respectively (no significant differences in both eyes). No significant differences between right and left eyes were detected for any GDx parameters. All parameters showed small right-left differences. The CVs (SD/mean x 100) for all parameters were less than 10%. Highly significant correlations were seen between bilateral eyes for macular retardation (r = 0.936, p < 0.0001) or baseline values (r = 0.946, p < 0.0001). A significant correlation (r = 0.883, p < 0.0001) was also seen between macular retardation and baseline values.
  
  
  CONCLUSIONS
  Considering individual differences in corneal birefringence, GDx parameters obtained from a GDx FCC may be useful for the objective evaluation of time-related changes in individual eyes or for binocular comparisons in cynomolgus monkeys.
authors.affiliation: Department of Biofunctional Molecules, Gifu Pharmaceutical University, Japan.
authors.forename: Masamitsu
authors.initials: M
authors.lastname: Shimazawa
authors.forename: Takazumi
authors.initials: T
authors.lastname: Taniguchi
authors.forename: Masaaki
authors.initials: M
authors.lastname: Sasaoka
authors.forename: Hideaki
authors.initials: H
authors.lastname: Hara
mesh_terms: D000818:Animals; D001718:Birefringence; D003315:Cornea / Q000502:physiology*; D005654:Fundus Oculi; D007429:Intraocular Pressure; D007834:Lasers; D008252:Macaca fascicularis; D009412:Nerve Fibers / Q000648:ultrastructure*; D012029:Refraction, Ocular; D015203:Reproducibility of Results; D012160:Retina / Q000648:ultrastructure*; D013997:Time Factors