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Wendy Watkins Harrison, Nathan Biancardi, Jamison Langston, Russell Gray, Taylor Kneip, Reese Loveless, Kaila Osmotherly; The Effect of the Full Field ERG on a Subsequent Multifocal ERG. Invest. Ophthalmol. Vis. Sci. 2017;58(8):4882.
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© ARVO (1962-2015); The Authors (2016-present)
The clinical standards for multifocal electroretinogram (mfERG) call for adaption to normal room lighting before the mfERG. They also specify that completion of any assessments where bright lights are used, such as ophthalmoscopy, should be done after the mfERG to prevent excess stimulation of retinal cells. However, full field (FF) ERGs, which place bright flashes on the retina, are routinely performed prior to mfERGs in clinical settings. It is unclear from the literature if the FFERG has an impact on the mfERG. This study seeks to examine the effect of the FFERG on the mfERG when performed sequentially.
Thirty subjects (age 27.1 ± 3.5 years) with 20/20 vision and no retinal abnormalities were included. Subjects reported for two visits and were fully dilated to over 6 mm at both visits. At visit one a FFERG was recorded (VERIS 6.2) using our clinical protocol which includes an ISCEV standard flash sequence with an additional 10.0 log bright flash; each flash condition was repeated 4-6 times. Following the FFERG, an mfERG was recorded using a 4 minute m-sequence at near 100% contrast (VERIS FMSII). At visit two only the mfERG was recorded. A burian-allen contact lens electrode filled with celluvisc was used for all recordings with a ground clip on the earlobe. The two mfERGs were compared for foveal and overall implicit time (IT) and amplitudes (amp). Paired t-tests were used to evaluate the data.
There was a small but statistically significant difference in foveal amplitudes (p=0.004) wherein the amplitude was larger following the FFERG stimuli. When examining individuals this was true for 24 of the 30 subjects. The mean difference was 11.1 nV (100.9 nV vs 89.8nV). There was no difference in foveal IT (p=0.66). There was no difference in overall IT or amp when averaging the entire eye (p=0.27 amp and p=0.56 IT). Qualitative noise between the two recordings did not appear to differ.
The small difference in foveal amplitude is most likely the result of a small long term cone adaptation but further studies are needed here. While it is statistically significant, the small difference of 11 nV is unlikely to be clinically important. These results should help increase clinical confidence in mfERG results when recorded following a FFERG.
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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