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C.B. Y. Kim, J.N. Ver Hoeve, P.L. Kaufman, T.M. Nork; Effect of Reference Electrode Location on Multifocal Electroretinograms in Cynomolgus Monkeys . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3423.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:To determine differences in the quality of multifocal electroretinography recordings using disparate reference electrode placements. Methods: Multifocal electroretinograms (mfERGs) were obtained from 12 female (weight: 1.9 to 4.0 kg) and 8 male (weight: 2.8 to 5.9 kg) cynomolgus monkeys. VERIS ScienceTM 4.9 (and 4.1) was used for stimulus generation, presentation, data collection, and preliminary analyses. 103 equal–sized hexagonal elements, which subtended ± 44 deg about the central visual axis, were displayed on a 21" monochromatic stimulus monitor. A binary m–sequence (214–1) with 13.33–ms base period was used. Mean luminance of the stimulus display was 100 cd/m2. Pupils were fully dilated. ERG–JetTM corneal contact lens electrodes were applied to both eyes. Each corneal electrode was referenced to a subdermal needle electrode that was situated on the ipsilateral outer canthus (I) and to the contralateral corneal electrode (C). The mfERG from the two electrode montages was recorded simultaneously on two A/D channels. Testing was monocular with the nontested eye covered with an opaque occluder. Order of ocular testing was randomized. Root mean square (RMS) of the low pass– (< 80 Hz) and high pass– (> 80 Hz) filtered mfERG waveforms was estimated for the first–order kernel (K1) response amplitude and oscillatory potentials (OP), respectively. RMS of the signal–containing portion (10–50 ms) of the K1 waveform and a subsequent portion (80–120 ms) that had returned to baseline, and considered as an estimate of noise, were averaged in 4 rings radiating from the foveal element. Separate repeated measures analyses of variance tested the effect of retinal eccentricity (ring), reference electrode location, and gender on K1 amplitude and OP RMS. Results:RMS of the K1 amplitude and OP was significantly larger (p=0.001) with the C– than with the I–montage. However, signal–to–noise ratios of the RMS measures were significantly higher (p<0.0005) with the I– than with the C–montage. Gender effects were not found. Conclusions: A variety of reference electrode configurations has been used in the study of nonhuman primate mfERG. This study found that a subdermal electrode located near the ipsilateral outer canthus resulted in higher signal–to–noise ratios than using the contralateral eye as a reference. Therefore, the ipsilateral reference montage is preferable in mfERG studies using similar recording conditions.
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