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Rotem Kimia, Ronald M Hansen, Anne Moskowitz, Anne B Fulton; Comparison of ERG responses obtained using a portable device and a conventional recording system. Invest. Ophthalmol. Vis. Sci. 2017;58(8):4887.
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In pediatric centers, full-field electroretinography (ffERG) may be performed under anesthesia because of age or behavioral issues. The RETevalTM (LKC Technologies, Inc.) is a portable ERG device that uses skin electrodes and does not require pupil dilation. The aim of this study is to compare RETeval results to results obtained with a conventional ERG device (e2 and ColorDome; Diagnosys LLC).
Full-field ERGs were recorded from 12 healthy dark-adapted adult volunteers (median age 22.5, range 20-39 years) using both recording systems. For the RETeval, pupils were undilated; a strip electrode array containing an active, a reference and a ground electrode was placed on the skin overlying the inferior orbital rim; and responses were recorded to the five standard ISCEV stimulus conditions. For the e2, one pupil was dilated; a bipolar Burian-Allen contact electrode was placed on the cornea and a ground electrode over the mastoid; and responses were recorded to series of scotopic flashes (dark adapted, ~5 log range, blue) and photopic flashes (white background, ~2.4 log range, red). The ISCEV stimuli were included in these stimulus series. Amplitude and implicit time of the a- and b-waves were measured.
Across the five ISCEV conditions, RETeval amplitudes were approximately 15% that of e2, and the average coefficient of variation was approximately 1.6 times larger for the RETeval amplitude data [mean (SD) 0.348 (0.041)] than for the e2 amplitude data [mean (SD) 0.222 (0.037)]. For the ISCEV scotopic conditions, a-wave and b-wave amplitude [Spearman’s rho; a-wave R=0.46, p<0.05; b-wave R=0.57, p<0.05] and implicit time [a-wave R=0.69, p<0.01; b-wave R=0.81, p<0.01] recorded by the RETeval correlated to e2 a-wave and b-wave amplitude and implicit time. Photopic and 30 Hz flicker measures obtained by the RETeval did not correlate to e2 measures.
While correlation was demonstrated, caution should be exercised translating results from one device to another. The high coefficient of variation indicates that larger sample sizes are needed to achieve similar statistical power. High variability may be a consequence of using a skin electrode. In a previous study, we found that the coefficient of variation for skin electrodes was 0.32 compared to 0.19 for Burian-Allen contact electrodes for subjects tested with dilated pupils and the conventional ERG.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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