Validating skin electrodes: Paving the way for non-invasive ERG use in psychiatry

Electroretinography (ERG) shows promise for identifying psychiatric biomarkers. The gold-standard approach relies on Dawson-Trick-Litzkow (DTL) electrodes and desktop equipment, but high costs and the expertise required for reliable electrode placement limit its implementation. This study evaluates a cost-effective alternative: a handheld ERG device paired with less invasive self-adhesive skin electrodes, which require minimal training.

ERG responses to cone and rod luminance stimuli were recorded from 49 participants: 15 controls (8 women, 7 men), 18 with bipolar disorder (12 women, 6 men), and 16 with schizophrenia (4 women, 12 men). Each participant underwent ERG testing with both electrode types.

Skin electrodes produced significantly smaller amplitudes and shorter latencies than DTL electrodes, except for longer scotopic b-wave latency. Women showed higher amplitudes and shorter latencies than men for both electrode types, with the photopic a-wave amplitude relative difference doubling when using skin electrodes. Reproducibility between eyes was high for both electrode types, though slightly lower for photopic a-wave with skin electrodes (ICC 0.76 vs. 0.86 for DTL).

Skin electrodes paired with handheld ERG devices offer a viable, accessible alternative to traditional DTL electrodes paired with desktop equipment. This approach has the potential to expand the applicability of ERG in clinical settings by addressing barriers like cost, complexity, and invasiveness, while highlighting the need to consider sex differences in ERG assessments, particularly with skin electrodes.