title: Inter-ocular and inter-session reliability of the electroretinogram photopic negative response (PhNR) in non-human primates.
abstract: OBJECTIVE
  To assess the inter-ocular and inter-session reliability for a range of parameters derived from the photopic electroretinogram (ERG) in a group of normal non-human primates.
  
  
  METHODS
  Inter-ocular differences for photopic ERGs were assessed in a group of normal anesthetized adult rhesus monkeys (Macaca mulatta, n=29); inter-session reliability was assessed for 23 eyes of 23 animals tested 3 months later. Signals were acquired using Burian-Allen contact lens electrodes, whereby the contralateral cornea served as a reference. Photopic ERGs were elicited using red Ganzfeld flashes (-0.5-0.67 log photopic cd.sm(-2)) on a rod suppressing blue-background (30 scotopic cdm(-2)). Measurement reliability was established for a-wave, b-wave, photopic negative response (PhNR) and oscillatory potential (OP) amplitudes, as well as for their implicit times, by calculation of the 95% limits-of-agreement (LOA) and the coefficient-of-variation (COV) for each parameter.
  
  
  RESULTS
  OP and a-wave amplitudes increased with intensity up to 0.67 log photopic cd.sm(-2), following a typical saturating function, whereas b-wave and PhNR amplitudes both declined above 0.42 log photopic cd.sm(-2). Inter-session variability was greater than inter-ocular variability. The inter-session COVs for PhNR amplitude (10-20%) were similar to the other photopic ERG components (a-wave: 12-17%, b-wave: 12-17%, OPs: 13-19%). Inter-session LOAs were also similar across components, but on average, were smallest for responses to moderate intensities (0.0-0.42 log photopic cd.sm(-2)).
  
  
  CONCLUSIONS
  In non-human primates, the 95% LOA for inter-session measurements of the photopic ERG a-wave, b-wave, OPs and PhNR are all similar. Inner-retinal damage may best be measured using the PhNR amplitude for moderately bright stimulus intensities. B-wave and PhNR amplitudes for brighter flashes are smaller and more variable. The ratio of PhNR:b-wave amplitudes manifests smaller variability and may therefore be useful for detection of selective PhNR loss.
authors.affiliation: Discoveries in Sight, Legacy Clinical Research and Technology Center, 1225 NE Second Avenue, Portland, OR 97232, USA. bfortune@discoveriesinsight.org
authors.forename: Brad
authors.initials: B
authors.lastname: Fortune
authors.forename: Bang V
authors.initials: BV
authors.lastname: Bui
authors.forename: Grant
authors.initials: G
authors.lastname: Cull
authors.forename: Lin
authors.initials: L
authors.lastname: Wang
authors.forename: George A
authors.initials: GA
authors.lastname: Cioffi
mesh_terms: D000704:Analysis of Variance; D000779:Anesthetics, Local / Q000494:pharmacology; D000818:Animals; D004596:Electroretinography / Q000187:drug effects / Q000379:methods* / Q000592:standards; D005260:Female; D008253:Macaca mulatta; D010775:Photic Stimulation / Q000379:methods; D015203:Reproducibility of Results; D013779:Tetrodotoxin / Q000494:pharmacology
chemical_list: D000779:Anesthetics, Local; D013779:Tetrodotoxin