Foveal amplitudes of multifocal electroretinograms are larger following full-field electroretinograms
The clinical standards for multifocal electroretinograms (mfERG) call for adaption to normal room lighting before the mfERG begins. They specify that any assessments where bright lights are used, should be done after the mfERG to prevent excess stimulation of retinal cells. However, full-field electroretinograms (FFERG) are performed prior to mfERGs in some clinical settings. It is unclear from the literature whether 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 young healthy subjects (age 27.1 ± 3.5 years) were included. Patients reported for two visits and were fully dilated at both visits. At visit one, a FFERG was recorded (VERIS 6.2) using our clinical protocol which includes an ISCEV standard flash sequence; each flash condition was repeated 4–6 times. Following the FFERG, an mfERG was recorded using a 4-min m-sequence at near 100% contrast. At visit two, only the mfERG was recorded. A Burian–Allen contact lens electrode filled with celluvisc was used for all recordings. The two mfERGs were compared for foveal, peripheral, and overall implicit time (IT) and amplitudes (amp). Paired t tests were used to evaluate the data. Coefficient of variation and Bland–Altman analysis was also reported for this patient group.
There was a small but statistically significant difference in foveal amplitudes (amp) (p = 0.004) wherein the amp was larger following the FFERG stimuli. The mean difference was 11.1 nV/deg2 (100.9 nV vs 89.8 nV). 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 = 0.44 amp and p = 0.54 IT) or just evaluating the periphery (p = 0.87 amp and p = 0.051 IT). Bland–Altman analysis found a coefficient of repeatability overall was 1.57 ms (IT) and 10.7 nV/deg2 (amp).
The difference in foveal amplitude is likely the result of a small long-term cone adaptation, but further studies are needed. While it is statistically significant, the small difference is unlikely to be clinically important. These results should help increase clinical confidence in mfERG results when recorded following a FFERG.
KeywordsmfERG Full-field ERG Lighting Adaptation
We would like to thank Dr. Marcus Bearse for his guidance as this project was formed. We thank Brian Colburn, Chris Johnson, and Zak Nelson for their help in follow-up data. We also thank Vicki Kimberlin, Donna Oller, and Julie Welch for their assistance in the Midwestern Eye Institute. We thank Kimberly Thompson for her help with figures. This work has been partially presented at the 2017 ARVO meeting and the 2018 ISCEV@ARVO meeting.
This study was funded by an internal grant to Wendy Harrison and Kaila Osmotherly from the Midwestern University Office of Research and Sponsored Projects.
Compliance with ethical standards
Conflict of interest
Wendy Harrison declares she has no conflict of interest. Kaila Osmotherly declares she has no conflict of interest. Nathan Biancardi declares he has no conflict of interest. Jamison Langston declares he has no conflict of interest. Russell Gray declares he has no conflict of interest. Taylor Kneip declares he has no conflict of interest. Reese Loveless declares he has no conflict of interest.
Statement of human rights
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Statement on the welfare of animals
There were no animals used in this study.
Informed consent was obtained from all individual participants included in the study.
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