May 2007
Volume 48, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2007
Comparing ERG Changes With RNFL Changes in Experimental Glaucoma
Author Affiliations & Notes
  • N. V. Rangaswamy
    College of Optometry, University of Houston, Houston, Texas
  • X. Luo
    College of Optometry, University of Houston, Houston, Texas
  • A. S. Vilupuru
    College of Optometry, University of Houston, Houston, Texas
  • R. S. Harwerth
    College of Optometry, University of Houston, Houston, Texas
  • L. J. Frishman
    College of Optometry, University of Houston, Houston, Texas
Investigative Ophthalmology & Visual Science May 2007, Vol.48, 1300. doi:
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      N. V. Rangaswamy, X. Luo, A. S. Vilupuru, R. S. Harwerth, L. J. Frishman; Comparing ERG Changes With RNFL Changes in Experimental Glaucoma. Invest. Ophthalmol. Vis. Sci. 2007;48(13):1300.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose:: To examine the relationship between the photopic negative response (PhNR) or oscillatory potentials (OPs) of the ERG and changes in retinal nerve fiber layer thickness (RNFLT) in primate eyes with experimental glaucoma.

Methods:: ERG recordings were obtained differentially between the two eyes of 6 anesthetized macaque monkeys at various stages of laser-induced experimental glaucoma. PhNRs were obtained with full-field flash ERGs with brief red flashes on a rod-saturating blue background. OPs were obtained with slow-sequence multifocal ERGs (mfERGs) with the m-sequence slowed by interleaving 14 blank frames (~200 ms ISI). PhNR amplitude was measured from baseline, 65 ms after the brief flash, and high frequency OPs were extracted between 110-224 Hz and their amplitude measured as root mean square (RMS). OCT images of the retinal nerve fiber layer (RNFL) around the optic nerve head of both eyes were obtained with the Stratus OCT system using standard high density scans. Visual field defects were assessed using behavioral static perimetry.

Results:: PhNR and summed OP amplitudes decreased with worsening MD of the visual fields, and the correlations were significant (r=0.77, r=0.70; p<0.01). While both PhNR and summed OP amplitudes showed significant correlations with the RNFLT at all locations, PhNR amplitude showed higher correlation (r=0.81-0.93) than the summed OP amplitude (r=0.69-0.81). OPs in the central 5-12o radius showed the highest correlation with the RNFLT and within this central region, OPs in the temporal retina were significantly larger than the OPs in the nasal retina (p<0.01) consistent with previous studies. The OP RMS in this location showed the strongest correlations with the superior (r=0.85) and inferior (r=0.79) RNFLT that correspond to the regions that receive nerve fibers from this location. At any stage of glaucoma, the local visual field defect, the OP amplitude loss and the corresponding RNFLT decrease were higher in the central temporal retinal location than the nasal retinal counterpart.

Conclusions:: PhNR and OP amplitudes reduced significantly as a function of RNFL loss in experimental glaucoma, which is consistent with a ganglion cell origin for these potentials. The temporal retina in the central 5-12o and its corresponding regions around the optic nerve head (superior and inferior) may be optimal locations to monitor progression of glaucoma.

Keywords: electroretinography: non-clinical • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • ganglion cells 
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