Abstract
Purpose :
Measurements of the pattern electroretinogram (pERG) and of the photopic negative response (PhNR) have been used to evaluate inner-retinal function in humans and in animal models of disease. The purpose of this study was to determine the correlation between these two electrophysiological measures using a commercially-available electrophysiology system.
Methods :
6-month-old, wild-type C57BL/6J female mice were tested (N = 9). Stimuli were generated by a Celeris rodent ERG system (Diagnosys, LLC, MA, USA), which was also used to record the ERG signals. The PhNR was elicited by a 20-cd-s-m-2 white flash presented against a 40 cd/m2 green adapting field. The flashes were presented at a rate of 2 Hz and 200 response were averaged for analysis. The PhNR was calculated as the amplitude of the trough following the b-wave divided by the b-wave amplitude (PhNR/b). The pERG was elicited by a contrast reversing bar stimulus (bar width: 0.06 cycles/degree; mean luminance: 50 cd/m2; reversal rate: 2.1/sec); 400 sweeps were averaged for analysis. The pERG waveform was characterized by a positive peak (P) followed by a negative trough (N). pERG amplitude was defined in two ways: 1) baseline to N (“N”); 2) P-to-N.
Results :
The PhNR amplitude ranged from 2.6 to 11.3 μV and the latency ranged from 91.1 to 182.5 ms. The PhNR/b amplitude ratio ranged from 0.08 to 0.20. The pERG N ranged from 0.8 to 3.7 μV, whereas the pERG P-to-N ranged from 2.0 to 8.2 μV. The coefficient of variation (standard deviation/mean) was 0.30, 0.49, and 0.44 for the PhNR/b, P-N, and N amplitudes, respectively. The PhNR/b ratio was not correlated with pERG P-to-N (r = 0.25, p = 0.52), but was correlated significantly with pERG N (r = 0.70, p = 0.04).
Conclusions :
The significant correlation between the PhNR/b ratio and the pERG N component suggests that these measures may share a common retinal source. Although the variability among measures is similar, PhNR measurement may have practical advantages over pERG recordings in rodent models.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.