Prevalence of electronegative electroretinograms in a healthy adult cohort

Abstract

ObjectiveAn electronegative electroretinogram (ERG) can indicate important ocular or systemic disease. This study explored the prevalence of electronegative responses to dark-adapted stimuli in a largely healthy cohort.Methods and Analysis211 participants recruited from the TwinsUK cohort underwent ERG testing incorporating international standard (International Society for Clinical Electrophysiology of Vision (ISCEV)) protocols and additional stimuli. Responses were recorded using conductive fibre electrodes, following pupil dilation and 20 min dark adaptation. Responses analysed were to the ISCEV standard and strong flashes (3.0 and 10 cd/m2 s), and to additional white flashes (0.67–67 cd/m2 s). A-wave and b-wave amplitudes were extracted; b:a ratios were calculated and proportions of eyes with ratios<1 were noted.ResultsMean (SD) age was 62.4 (11.4) years (median, 64.3; range 23–86 years). 93% were female. Mean (SD) b:a ratios for right and left eyes, respectively, were 1.86 (0.33) and 1.81 (0.29) for the standard flash, and 1.62 (0.25) and 1.58 (0.23) for the stronger flash; average b:a ratio was lower for the stronger flash (p<0.0001). No waveforms were electronegative. For additional flashes, b:a ratio decreased with increasing flash strength. No electronegative waveforms were seen except in three eyes (0.7%) for the strongest flash; in some cases, drift in the waveform may have artefactually reduced the b:a ratio.ConclusionFor standard dark-adapted stimuli, no participants had electronegative waveforms. The findings support the notion that electronegative waveforms (in response to standard flash strengths) are unusual, and should prompt further investigation.

Electronegative electroretinogram in the modern multimodal imaging era

“…Recently an evaluation of a normal population found no electronegative ERGs in an adult cohort (211 subjects) using standard ISCEV DA 3.0 flash stimulus and borderline electronegative ERG in three patients using the stronger flash DA10.0 (67 cd/m 2 s), endorsing the concept that a dark adapted electronegative ffERG is abnormal and requires further evaluation. 30 Photoreceptor dystrophy, CSNB, ischemia, and retinoschisis were the most common aetiologies associated with an electronegative ERG in our cohort. This is comparable to previous studies using a similar classification.…”

“…When this functional data is combined with multimodal retinal imagining, a more precise clinical diagnosis can be made, even in normal or near normal fundal appearances. Recently an evaluation of a normal population found no electronegative ERGs in an adult cohort (211 subjects) using standard ISCEV DA 3.0 flash stimulus and borderline electronegative ERG in three patients using the stronger flash DA10.0 (67 cd/m 2 s), endorsing the concept that a dark adapted electronegative ffERG is abnormal and requires further evaluation 30 …”

Cone-driven strong flash electroretinograms in healthy adults: Prevalence of negative waveforms

“…The International Society for Clinical Electrophysiology of Vision (ISCEV) standard for full-field electroretinography specifies three flash strengths to be delivered in the dark, the strongest of which is termed the DA10 stimulus (corresponding to 10 photopic cd m −2 s) [ 1 , 2 ]. Negative waveforms, in which the b-wave amplitude is selectively attenuated such that it is smaller than the a-wave amplitude, are not typically observed in healthy people in response to standard flash stimuli [ 3 ] and usually indicate loss of post-receptoral signals [ 4 , 5 ]. However, in some conditions when rod photoreceptor responses are lost completely, the dark-adapted ERG represents a cone-driven response.…”

“…Over 200 healthy adult volunteers from the TwinsUK cohort were previously recruited to undergo full-field ERG recordings in response to ISCEV standard stimuli and also to a range of experimental protocols [ 3 , 16 ]. These included responses to white flashes of similar strength to the ISCEV standard strong flashes, but delivered in the presence of a dim blue rod-saturating background.…”

“…These included responses to white flashes of similar strength to the ISCEV standard strong flashes, but delivered in the presence of a dim blue rod-saturating background. We previously found that no participant showed a negative waveform in response to this flash strength when delivered in the dark [ 3 ]. The primary purpose of the present study was to investigate the response to such a flash when delivered in the presence of the blue rod-saturating background and to determine the proportion of these responses that showed a negative waveform (b/a ratio less than 1).…”