Purchase this article with an account.
Abdullah Abou-Samra, Gonzalo Ortiz, Radouil T Tzekov; Red flash on blue background as a stimulus for photopic negative response in clinical settings. Invest. Ophthalmol. Vis. Sci. 2019;60(9):2508.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
The photopic negative response (PhNR) is a component of the full-field electroretinogram (ERG), with strong input from retinal ganglion cells, which varies with several ophthalmic pathologies. The International Society for Clinical Electrophysiology of Vision (ISCEV) currently recommends a red flash stimulus on a blue background (ROB) as an optimal way to elicit PhNR. The purpose of this study is to compare PhNR parameters in patients between two conditions: ROB and Photopic 3.0 ERG (Ph3).
A retrospective analysis of the records of patients undergoing routine clinical full-field ERG testing at the USF Eye Institute (Tampa, FL) was conducted. ERGs were recorded on a UTAS E3000 system (LKC Technologies) with DTL electrodes. All records had to have recordable PhNR response under 2 conditions: ROB of 1.3 cd.s/m2 flash intensity on a 28 cd/m2 background and a stimulation rate of 2.8Hz; a standard ISCEV Ph3 response. PhNR was measured at two locations: before the i-wave (PhNR1) and after the i-wave (PhNR2). A Wilcoxon matched pair signed ranked test was performed as data was not normally distributed.
A total of 84 patients / 160 eyes (28M, 56 F; mean age 55.9 +/- 16 years) were evaluated and had recordable PhNR under ROB stimulation: PhNR1 was identifiable in 129 eyes (86.9%) and PhNR2 in 89 eyes (55.6%). In a subset of patients matched for having recordable Ph3 (154 eyes), a paired comparison was made for the amplitude of PhNR2 (ROB vs. Ph3); the difference was not significant (p>0.05). The recordability of PhNR peaks in ROB vs. Ph3 was 87.0% vs. 97.4% (PhNR1) and 55.8% vs. 76.0% (PhNR2). In that subset, PhNR2 had an average peak time of 74.5 +/- 10.6 msec, slower than the corresponding time in Ph3 (66.3+/-6.6 msec). Only 50% of PhNR2 peak times were identified within the interval 65-75 msec, while this percent was even lower for the Ph3 condition (40.2%).
In this clinical population and under the conditions used for recording, the amplitudes of PhNR2 (typically used as a measure for the response) were similar between the ROB and Ph3 conditions. Given the lower recordability of PhNR2 under ROB, PhNR recorded under Ph3 can be used as an alternative condition to evaluate the response. A time interval suitable for averaging the trace in case distinct peak is difficult to identify should be carefully considered for reach recoding condition.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
This PDF is available to Subscribers Only