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Dinah Chen, Scott E Brodie; Quantitative calibration of sensor strip ERG electrodes – Update.. Invest. Ophthalmol. Vis. Sci. 2021;62(8):1346.
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© ARVO (1962-2015); The Authors (2016-present)
ERGs are traditionally recorded using corneal electrodes, which can be difficult for some patients to tolerate. In the last several years, adhesive skin electrodes have gained in acceptance. We have previously reported on the clinical usefulness of qualitative interpretation of ERG recordings using skin electrodes for a wide spectrum of retinal disorders, as well as a preliminary estimate of the quantitative comparison of simultaneous ERG recordings using contact lens (CL) and adhesive skin electrodes to compare differences in signal strength. In the present report, we update our quantitative findings.
The study was Institutional Review Board approved. 89 subjects were drawn from the practice of one of the authors who were referred for full-field ERG testing for multiple clinical indications. Informed consent was obtained from patients or accompanying parents. ERGs (obtained according to ISCEV standards) were recorded simultaneously from both eyes with ERG-jet corneal CL electrodes and LKC Technologies Sensor Strip adhesive skin electrodes using multi-channel instrumentation (Diagnosys LLC, Espion3). A- and b-wave amplitudes and implicit times were compared between the two electrode types.
Waveform morphologies were similar for both electrodes. Regression coefficients (conversion factors) for a- and b-wave amplitudes under photopic and scotopic conditions were tightly clustered: DA 0.01 b-wave: 0.368; DA 3 a-wave: 0.343; DA 3 b-w-wave: 0.360; LA 3 a-wave: 0.256; LA 3 b-wave: 0.325; 30-Hz flicker peak-to-peak: 0.384. Regression coefficients for implicit times were nearly equal to 1.0, indicating comparable latencies for skin and CL electrode recordings: DA 0.01 b-wave: 0.971; DA 3 a-wave: 0.926; DA 3 b-wave: 0.996; LA 3 a-wave: 0.967; LA 3 b-wave: 0.964. The regression coefficient for the entire amplitude data set was 0.336, with an overall correlation between skin and CL electrode amplitudes of 0.799. The regression coefficient for the entire implicit time data set was 0.980, with an overall correlation of 0.96.
Our best estimate for the conversion factor between ERG amplitudes recorded with adhesive skin electrodes and CL electrodes is 0.336 – skin electrode amplitudes are about 1/3 the amplitudes recorded simultaneously using CL electrodes - with a high correlation between skin and CL electrode amplitudes. Implicit times are nearly identical for the two electrode types.
This is a 2021 ARVO Annual Meeting abstract.
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