title: Comparison of guinea pig electroretinograms measured with bipolar corneal and unipolar intravitreal electrodes.
abstract: This study considers the precision and accuracy of bipolar corneal electrodes compared with unipolar intravitreal methods in collecting electroretinographic (ERG) recordings from a small animal. Flash ERGs were obtained from 9 adult guinea pigs on three occasions. Corneal bipolar (Burian-Allen) electrodes were used to collect data on the first two occasions whereas unipolar intravitreal electrodes were used on the last. We identified the a-wave, b-wave, oscillatory potentials, PIII and PII responses. Intensity-response functions were fit using a Naka-Rushton relationship with a bootstrap estimating the 95% confidence limits. Discrepancy analysis was applied to determine the coefficient of agreement. We found significantly larger amplitudes with unipolar intravitreal electrodes (ANOVA; a-wave, p<0.002; b-wave, p<0.001; Oscillatory potentials (OPs), p<0.005) especially at high intensities. Implicit times showed little differences between electrodes for the a-wave, significantly faster (p<0.03) b-waves at some intensities, and significantly slower (p<0.005) OP implicit times across all intensities. The PIlI amplitude (log microV), sensitivity and timing were not significantly different (p>O.05) if expressed in logarithmic units but PII amplitude (log microV) was significantly smaller with corneal electrodes. We suggest that a conversion factor (x1.35) should be applied to data collected with bipolar corneal electrodes to estimate the amplitudes of the modelled parameters accurately. The corneal electrode gave a precision of +/-39 microV which yields a statistical power of 0.90 for a sample size of 7 subjects. We conclude that bipolar corneal electrodes provide smaller electroretinogram amplitudes due to their location and reduced span of the retinal generators.
authors: Department of Optometry and Vision Sciences, University of Melbourne, Parkville, Victoria, Australia.
authors: B V
authors: BV
authors: Bui
authors: H S
authors: HS
authors: Weisinger
authors: A J
authors: AJ
authors: Sinclair
authors: A J
authors: AJ
authors: Vingrys
mesh_terms: D000818:Animals; D003315:Cornea; D004596:Electroretinography / Q000295:instrumentation*; D005260:Female; D006168:Guinea Pigs; D008297:Male; D008839:Microelectrodes; D015588:Observer Variation; D010775:Photic Stimulation; D015203:Reproducibility of Results; D012160:Retina / Q000502:physiology*; D014822:Vitreous Body