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Katherine Tsay, Sara Safari, Radouil T Tzekov; Does red flash on a blue background result in more eyelid muscle activity compared to white flash on a white background?. Invest. Ophthalmol. Vis. Sci. 2022;63(7):4540 – F0327.
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According to the extended protocol for the photopic negative response (PhNR) of the full-field electroretinogram from the International Society for Clinical Electrophysiology of Vision (ISCEV), the preferred method of eliciting PhNR is a red flash on a rod saturating blue background (ROB). However, PhNR can also be elicited by a white flash on a white background, under stimulus conditions like the one used to elicit an ISCEV standard Photopic 3.0 ERG (Ph3) response. The purpose of the current study is to compare the baseline noise between the two conditions in patients with various retinal pathologies.
A retrospective chart review and data analysis of patients aged 18 and over undergoing routine ERG testing at the University of South Florida Eye Institute (Tampa, FL) between July 2018 and October 2021 were conducted. Throughout the study period, Ph3 was recorded in the same way while ROB response was generated in three different ways, resulting in three comparison groups. Group 1 (Gr1) ROB protocol used a ~5 cd●s/m2 red flash (627 nm) on a 30 cd/m2 blue background (470 nm), Group 2 (Gr2) protocol used a ~2.5 cd●s/m2 red flash on a 10 cd/m2 blue background, while Group 3 (Gr3) protocol used a ~5 cd●s/m2 red flash on a 10 cd/m2 blue background. The level of background bioelectrical activity (30 ms before the flash) was compared between the Ph3 and ROB conditions by calculating the root mean square (RMS) of the signal under all three protocols.
The records of 69 patients/138 eyes (19M, 50F, mean age 50.7 +/- 14.5 years) were evaluated (Gr1=14; Gr2=27; Gr3=28). The baseline level of activity was higher in all three ROB conditions compared to Ph3 for both right (OD) and left (OS) eyes. Specifically, in Gr1, OD RMS = 0.95 µV (Ph3) vs. 1.66 µV (ROB) (p=0.003, Wilcoxon matched-pairs signed-rank test) and OS RMS = 1.1 vs. 1.7 µV (p=0.006); in Gr2, OD RMS = 0.80 vs. 1.98 µV (p=0.0003) and OS RMS = 0.90 vs. 1.79 (p<0.0001); in Gr3, OD RMS = 0.87 vs. 1.27 µV (p<0.0001) and OS RMS = 0.96 vs. 1.14 µV (p=0.02).
Baseline activity was higher under ROB stimulation in all conditions compared to Ph3, indicating more eyelid muscle activity and a higher level of visual discomfort consistent with anecdotal patient reports. The results of our study suggest that a white flash on a white background may reduce patient discomfort while generating a comparable PhNR.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.
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