DTL versus skin electrodes in recording of multifocal pattern electroretinogram and multifocal photopic negative response.

Objective: To compare the photopic negative response of the multifocal ERG (mfERG_PhNR) and the multifocal pattern electroretinogram (mfPERG) using DTL electrode (E_DTL) vs skin electrode (E_SKIN) in healthy young and old adults.

Methods: Ten "Young" [20-27 years] and eight "Old" [60-72 years] participants took part in this study. The electrophysiological responses were recorded binocularly using E_DTL and E_SKIN. 5-way ANOVAs were applied to investigate the following factors on mfERG_PhNR: i) ELECTRODE, ii) DILATATION, iii) AGE, iv) EYE, and v) ECCENTRICITY. For mfPERG, the same factors, except dilatation, were investigated applying 4-way ANOVAs. These were conducted for amplitude and peak time of different components as well as signal-to-noise-ratio (SNR).

Results: Amplitudes of mfERG_PhNR [mfPERG]-based E_SKIN recording were reduced to 32-38% [37-38%] compared to E_DTL, $p<0.001$ . This corresponded to SNR reduction to 80% [60%], $p<0.001$ . E_SKIN based responses had shorter peak times, by 0.2-0.5 ms for N1 and P1, $p<0.05$ , [P1: 1.5 ms, $p<0.001$ ]. Both age groups had comparable amplitudes and SNRs, but Young had shorter peak times, by 1.5-2.2 ms for N1 and P1, $p<0.05$ [3.7-4.2 ms for N1, P1, N2, $p<0.05$ ]. Compared to dilated recordings, undilated mfERG_PhNR amplitudes were reduced to 47-87%, $p<0.01$ , and peak times were delayed by 2.0-11.8 ms, $p<0.001$ .

Conclusions: mfPERG & mfERG_PhNR traces were similar for E_DTL and E_SKIN. However, for skin electrodes, amplitudes and SNRs were lower and peak times shorter. E_SKIN thus seem to be a viable alternative in patients in whom the use of corneal electrodes is precluded, e.g., children and disabled patients, but at the expense of SNR and with reference to E_SKIN normative data.