Abstract
PurposeThis study sought to investigate whether there is an optimal position of the Dawson, Trick, and Litzkow (DTL) electrodes when measuring the full-field electroretinogram (ERG) for monitoring purposes.MethodsIn 200 uveitis patients, an extended light-adapted (LA) ERG protocol was measured twice, incorporating the International Society for Clinical Electrophysiology of Vision standards. First, a LA ERG was measured with the DTL in the lower lid position (LLP) and thereafter in the fornix position. Differences in amplitudes and implicit times of a-waves, b-waves, and the 30 Hz peak were investigated. Intraclass correlation coefficients (ICCs) as well as coefficients of variation (CoV) were calculated, to assess both reliability and relative variability between the two DTL positions.ResultsImplicit times showed no statistically significant differences between the two DTL positions. As expected, amplitudes at the different stimulus strengths were 1.12–1.19 higher in the LLP, but there were no significant differences in the CoV between the two DTL positions. The ICC was high for the b-wave and 30 Hz flicker response (0.842–0.979), but lower for the a-wave, especially for amplitudes (0.584–0.716).ConclusionsFor monitoring purposes in patients, we conclude that based on relative variability, no position is preferable above the other. However, because in most diseases amplitudes are decreased, the LLP may be chosen because it yields higher amplitudes. Whatever the choice, it is important to ensure that the DTL position remains stable during an ERG recording.
Highlights
Since the introduction of the Dawson, Trick, and Litzkow (DTL) electrode [1], its use in recording electroretinograms (ERGs) has spread
Amplitudes at the different stimulus strengths were 1.12–1.19 higher in the lower lid position (LLP), but there were no significant differences in the coefficients of variation (CoV) between the two DTL positions
Median amplitudes were significantly higher, and amplitude ranges were wider for all responses recorded with LLP compared to the fornix position (FP)
Summary
Since the introduction of the Dawson, Trick, and Litzkow (DTL) electrode [1], its use in recording electroretinograms (ERGs) has spread. One of the main advantages of the DTL is that it is much more comfortable to wear compared to conventional electrodes, such as contact lens electrodes [2,3,4]. The ERG was mainly used for diagnosing retinal diseases such as retinal dystrophies, where the ERG is frequently severely abnormal. That the ERG is increasingly used for monitoring disease, more subtle ERG changes become important. One must be aware of factors that may affect the ERG results, other than disease or treatment. Factors that influence the inter-session variability are important
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