Abstract
Purpose :
The ISCEV extended protocol for recording of the photopic negative response (PhNR) recommends using red flashes on a blue background (RoB) as the preferred method. It has to be noted that the recorded signal represents a composite signal with different ERG components (a-, b-wave, oscillatory potentials (OPs), PhNR, etc.). Recently, some evidence has emerged that OPs may reflect retinal ganglion cell (RGC) function. Therefore, the purpose of the current study was to evaluate the characteristics of PhNR measured from the composite signal vs. measured from the filtered lower frequency signal (ERG – OPs).
Methods :
A retrospective data analysis of patients aged 18 and over undergoing ERG testing at USF Eye Institute (Tampa, FL) was conducted. The RoB signal was recorded binocularly using the SunBurst system (LKC Technologies) as part of the light-adapted clinical ERG after the LA3.0 ERG and 30 Hz flicker. For OP extraction, the signal was filtered using a high-pass 8th order Butterworth filter with a 58Hz cutoff. The PhNR measurement was done in two ways: before (PhNR1) and after the i-wave (PhNR2), as used before (Doc Ophthalmol 2020 140:115-128). For this study, the PhNR amplitudes measured in the ‘traditional’ way on the unfiltered signal (PhNR1-t, PhNR2-t) whereas the ones measured in the second way were referred to as ‘filtered’ (PhNR1-f, PhNR2-f). PhNR was considered recordable when a well-defined trough was present to indicate the maximum response.
Results :
The records of 70 patients/135 eyes (18M, 52F); mean age 49.2 ± 15.3 years were evaluated. The amplitude of PhNR1r was ~11% smaller compared to PhNR1-f for both right and left eyes (56.8 ± 18.0 vs 63.7 ± 19.2 µV right eyes, 53.1 ± 22.1 vs 59.8 µV ± 24.8 left eyes, p<0.0001, Wilcoxon test). The amplitude of PhNR2-f showed a similar decrease of ~8-12% (69.7 ± 20.8 vs 75.6 ± 22.0 right eyes, 65.6 ± 22.2 vs 74.4 ± 26.9 left eyes, p<0.0001, Wilcoxon test). For PhNR1 the recordability remained the same for both measures at 58.7% right eyes and 62.7% left eyes, while for PhNR2 the recordability of PhNR2-f was slightly higher at 50.8% (vs 49.2%) for right eyes and 47.5% (vs 39.0%) for left eyes.
Conclusions :
An increase in recordability for PhNR was observed in the residual measures compared to traditionally used measures. This could be helpful in improving the reliability of PhNR amplitude estimate in clinical settings.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.