title: Loss of the low-frequency component of the global-flash multifocal electroretinogram in primate eyes with experimental glaucoma.
abstract: OBJECTIVE
  To study relationships between glaucoma-sensitive components identified with frequency-domain analysis of global-flash multifocal electroretinogram (mfERG), regional retinal nerve fiber layer thickness (RNFLT), and local visual field sensitivity (VS).
  
  
  METHODS
  Eleven macaque monkeys, including four controls and seven with unilateral laser-induced trabecular meshwork scarification and ocular hypertension, were observed with optical coherence tomography (OCT), full-field light-adapted flash ERG, 103-hexagon global-flash mfERG (MFOFO), and static perimetry. The effects of experimental glaucoma on mfERG were assessed in the frequency domain. Relations between root mean square (RMS) amplitude of a glaucoma-sensitive frequency range and peripapillary RNFLT (standard 12° OCT circular scan), and between RMS amplitude and VS were studied.
  
  
  RESULTS
  Experimental glaucoma led to a dramatic and consistent power loss in the low-frequency (<25 Hz) band of mfERG. The RMS of this low-frequency component (LFC) correlated significantly with the regional RNFLT. The r(2) of linear fits was 0.39 (P < 0.001) for cross-sectional group data and 0.60 after correction for intersubject variability. The r(2) of linear fits for longitudinal data from individual animals was as high as 0.78 (P < 0.001). Local LFC RMS amplitude also correlated significantly with interpolated VS for hexagons. The r(2) for exponential fits of hexagon LFC RMS amplitudes (inner three rings) versus VS (dB) was 0.29 to 0.52 (P < 0.001) for the group and up to 0.95 in individuals.
  
  
  CONCLUSIONS
  The significant correlations between regional measures of global-flash mfERG, RNFLT, and VS suggest that LFC RMS amplitude provides a useful index for objective quantification of local RGC function and monitoring of early changes in glaucoma.
authors.affiliation: College of Optometry, University of Houston, Houston, Texas 77204-2020, USA.
authors.forename: Xunda
authors.initials: X
authors.lastname: Luo
authors.forename: Nimesh B
authors.initials: NB
authors.lastname: Patel
authors.forename: Ronald S
authors.initials: RS
authors.lastname: Harwerth
authors.forename: Laura J
authors.initials: LJ
authors.lastname: Frishman
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D004596:Electroretinography; D005260:Female; D005901:Glaucoma / Q000175:diagnosis / Q000503:physiopathology*; D053685:Laser Therapy; D008253:Macaca mulatta; D008297:Male; D009412:Nerve Fibers / Q000502:physiology*; D009798:Ocular Hypertension / Q000175:diagnosis / Q000503:physiopathology; D009901:Optic Nerve Diseases / Q000175:diagnosis / Q000503:physiopathology*; D010775:Photic Stimulation; D012165:Retinal Ganglion Cells / Q000502:physiology*; D041623:Tomography, Optical Coherence; D014129:Trabecular Meshwork / Q000601:surgery; D058609:Visual Field Tests; D014794:Visual Fields / Q000502:physiology