title: Measuring the Photopic Negative Response: Viability of Skin Electrodes and Variability Across Disease Severities in Glaucoma.
abstract: OBJECTIVE
  The purpose of this study was to determine the feasibility of measuring the photopic negative response (PhNR) of the full-field electroretinogram (ERG) using skin electrodes compared to conjunctival electrodes and its test-retest variability over a range of disease severities in open-angle glaucoma.
  
  
  METHODS
  Recordings were performed twice (100 sweeps each) within the same session in 43 eyes of 23 participants with glaucoma to determine its intrinsic variability. The ratio between the PhNR and B-wave amplitude (PhNR/B ratio) was determined for each trace and computed across 5 to 100 sweeps of each recording. Spectral-domain optical coherence tomography was used to measure the average peripapillary retinal nerve fiber layer (RNFL) thickness.
  
  
  RESULTS
  The PhNR/B ratio and its magnitude of variability were not significantly different between skin and conjunctival electrodes (P≤ 0.197), and the degree of variability decreased substantially with increasing number of sweeps. For skin electrodes, the intraclass correlation coefficient was 0.89 and 0.91 for right and left eyes, respectively. The variability of the PhNR/B ratio decreased with lower RNFL thickness values and larger B-wave amplitudes (P≤ 0.002).
  
  
  CONCLUSIONS
  Skin electrodes are a viable alternative to conjunctival electrodes when measuring the PhNR in open angle glaucoma, and increasing the number of sweeps substantially reduced its intrinsic variability; the extent of variability was also lower with worsening disease severity.
  
  
  CONCLUSIONS
  The feasibility of performing ERG recordings widely across a range of disease severities in glaucoma can be achieved through using skin electrodes and increasing the number of sweeps performed to improve measurement repeatability.
authors.affiliation: Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, East Melbourne, Australia ; Ophthalmology, Department of Surgery, The University of Melbourne, Melbourne, Australia.
authors.forename: Zhichao
authors.initials: Z
authors.lastname: Wu
authors.affiliation: Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, East Melbourne, Australia ; Ophthalmology, Department of Surgery, The University of Melbourne, Melbourne, Australia.
authors.forename: Xavier
authors.initials: X
authors.lastname: Hadoux
authors.affiliation: Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, East Melbourne, Australia ; Ophthalmology, Department of Surgery, The University of Melbourne, Melbourne, Australia.
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: Fan Gaskin
authors.affiliation: Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, East Melbourne, Australia ; Ophthalmology, Department of Surgery, The University of Melbourne, Melbourne, Australia.
authors.forename: Marc G
authors.initials: MG
authors.lastname: Sarossy
authors.affiliation: Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, East Melbourne, Australia ; Ophthalmology, Department of Surgery, The University of Melbourne, Melbourne, Australia.
authors.forename: Jonathan G
authors.initials: JG
authors.lastname: Crowston
keywords: electroretinogram; ganglion cell function; glaucoma; photopic negative response