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

Abstract

AbstractPurposeThe 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.MethodsIn 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).ResultsThe 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).ConclusionsWe 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.