Abstract
Purpose :
The photopic negative response (PhNR) of the cone electoretinogram (ERG) has been reported to deteriorate in diseases affecting retinal ganglion cells (RGCs). However, appropriate condition for the PhNR recordings has been undetermined. While white stimuli on a white background (W/W) is widely used for recording the cone ERG, red stimuli on a blue background (R/B) produced by LED may be suitable for eliciting large PhNRs. To determine the proper stimulus conditions for the PhNR , clinical significance of the PhNR was compared between W/W and R/B in glaucoma.
Methods :
Eighty eyes of 80 patients with open angle glaucoma (OAG) and 40 eyes of 40 age-matched normal subjects were studied. The cone ERGs were recorded using W/W and R/B. The stimulus and background lights were produced by LED, and their intensities were photopically matched between the two conditions. The intensity of the background light was 10 cd/m2, and that of stimuli was 0.5, 1.0, 2.0 or 3.0 cd-s/m2. The first and second troughs that appeared following the b-wave before and after the i-wave were designated as the PhNR1 and PhNR2, respectively. Thickness of the retinal nerve fiber layer (cpRNFL) around the optic nerve head were measured by SD-OCT. Mean deviation (MD) was determined by standard automated perimetry. Linear regression analyses were performed between the PhNR amplitude and cpRNFL or MD.
Results :
<span lang="EN-US" style="font-family:arial,sans-serif; font-size:12pt; margin:0px"><font color="#000000">Correlation coefficients between the PhNR1 amplitude and cpRNFL or MD were better under W/W (R=0.459-0.496 for the cpRNFL, R=0.450-0.487 for the MD) with steeper slopes compared to those under R/B (R=0.405-0.495 for the cpRNFL, R=0.381-0.483 for the MD). In contrast, the PhNR2 amplitude elicited by R/B (R=0.459-0.544 for the cpRNFL, R=0.414-0.543 for the MD) produced larger correlation coefficients with steeper slopes than by W/W (R=0.422-0.451 for the cpRNFL, R=0.358-0.448 for the MD). Slopes of the regression lines became steeper with increasing intensities of the stimuli. </font></span>
Conclusions :
Our results indicate that the PhNR1 and PhNR2 are suitable for measuring the RGC function in OAG when using W/W and R/B, respectively. The PhNR elicited by higher stimulus intensities may be more sensitive than by lower stimulus intensities in detecting functional and structural abnormalities of RGCs in OAG.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.