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Radouil T Tzekov, Gonzalo Ortiz, Connor Hyde; Full-field ERG measurements of the photopic negative response recorded under four different conditions in a clinical setting. Invest. Ophthalmol. Vis. Sci. 2017;58(8):4883.
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© ARVO (1962-2015); The Authors (2016-present)
Accurate and precise measurement of the full-field ERG photopic negative response (PhNR) could be very useful as an estimate of the retinal ganglion cell function in various ophthalmic diseases. The purpose of this work was to evaluate and compare PhNR parameters recorded under four different conditions in a clinical setting.
A retrospective analysis of the PhNR records of patients undergoing routine clinical full-field ERG testing at USF (Tampa, FL) was conducted. All records had to have recordable PhNR response under four different conditions: red flash on a white background of 30 cd/m2 (Condition #1); red flash on a dim blue background of 1.9 cd/m2 (Condition #2); red flash on a bright blue background of 28 cd/m2 and a stimulation rate of 1 Hz (Condition #3) and red flash on a bright blue background and a stimulation rate of 2.8 Hz (Condition #4). The intensity of the red flash was kept at 5.35 cd.s/m2 for all conditions. The PhNR was measured at two locations on the ERG trace: before the i-wave (PhNR#1) and after the i-wave (PhNR#2).
The records of 29 patients satisfied the criteria; one patient’s records contained significant artifacts; of the remining 28 patients, 10 were males (50.4 +/- 20.4 yrs.) and 18 were females (45.9 +/- 20.5 yrs.). Statistical analysis demonstrated that there was no difference in PhNR#1 amplitude between the four conditions. However, Condition #1 and Condition #2 showed larger PhNR#2 amplitude compared to Condition #4 (p<0.05). Correlations between PhNR#1 and PhNR#2 amplitudes were high (0.84, 0.73, 0.71, 0.89). PhNR amplitudes were more correlated with the amplitudes of the corresponding a-waves (range 0.12 to 0.63) compared to the amplitudes of the b-waves (range 0.002 to 0.24) for every condition. Eye movement artifacts were relatively infrequent and interfered more with the PhNR#2 (6.8%) vs. PhNR#1 (4.1%) responses. In two patients, reliable PhNR responses could not be recorded in Condition #4 and the magnitude of eye movement artifacts were more pronounced in that condition.
Some conditions were more favorable for acquiring a reliable PhNR response compared to others. The implications for introducing PhNR into the clinical ERG standard are discussed.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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