Influence of pre-adaptation time to background illumination on photopic negative response of the full-field electroretinogram

Abstract Purpose The photopic negative response (PhNR) is a negative wave (latency ~70ms) of the full-field electroretinogram (ERG) which represents ganglion cell activity. The amplitude is most distinctive for a red stimulus on a blue background. In the literature different pre-adaptation times (range from few seconds to 10min) to the blue background can be found. The aim of the study presented here was to verify whether the pre-adaptation time to the blue background has an influence on the PhNR wave. Methods In total 12 subjects (25.4±2.0years, 4m, 8f) participated in the study. For visual stimulation, a full-field stimulator with a red flash (wavelength: 625nm, flash strength: 1.5cds/m², duration: ≤ 5ms, inter-flash interval: 1s) on blue background (wavelength: 455nm, luminance: 10cd/m²) was used. For ERG recording, Ag/AgCl ring-shaped skin-electrodes were placed at the lower eyelid, the ipsilateral earlobe, and the forehead. The subjects were light adapted before all measurements. Each ERG measurement consisted of a pre-adaptation time (15s/1/2/5/10min, randomized order) followed by an ERG measurement, which includes 20 artifact-free sweeps. The PhNR wave was defined as the minimum after the b-wave in the latency range from 60 to 80ms and was measured from the baseline (BT) and from the b-wave peak (PT). For statistical analysis, the Friedman-test was applied between the pre-adaptation times for both measured amplitudes and the latency (α=0.05). Results The PhNR could be measured and analyzed from all subjects. The Friedman-test showed no significant difference between the pre-adaption times for both amplitudes and the latency (*p ≤ 0.0167; pBT-amplitude = 0.281, pPT-amplitude = 0.797, platency = 0.448). Conclusions We found no influence of the pre-adaption time to the blue background on the PhNR amplitude and latency. Therefore, for future work only a short pre-adaptation time of a few seconds is sufficient for a stable PhNR wave measurement for light adapted subjects.