Electrode comparison in pattern electroretinography

In recent years, there has been great interest in recording the pattern electroretinogram (PERG) in glaucomatous and diabetic populations. The Dawson, Trick, and Litzkow thread electrode (DTLTE) and the gold foil electrode (GFE), commonly used for recording PERGs, were compared for variations in amplitude of response, test-retest variability, and patient comfort. Two study centers collected data on a total of 32 normal subjects. The subjects from the London center showed a slight (but not significant) preference for the DTLTE, and the Houston subjects also found the DTLTE to be significantly more comfortable (chi-square = 39, P < 0.001). In both study groups, the GFE was found to produce a statistically larger amplitude of response than that obtained with the DTLTE. Significant differences were found regardless of the slow (transient, 3.1 Hz; F = 6.24; P = 0.0192) or fast (steady state, 8.3 Hz; F = 18.38; P = 0.0001) stimulus-presentation rate. Larger differences between the two electrodes occurred under steady- state conditions. Although there is no consensus as to the optimum recording conditions to obtain the subtle PERG, it appears the GFE records larger responses than the DTLTE. However, test-retest data confirmed that the GFE records twice the amplitude of the DTLTE, and it also produced twice the variability (average percent difference over time for GFE, 15%; for DTLTE, 8%).