Full-field electroretinography reference limits from 420 healthy subjects, derived from transference and validation of reference data between electrode types and centers

Abstract

Purpose : The objective was to establish age-adjusted reference intervals for the full-field electroretinogram (ERG) recorded with silver thread electrodes.

Methods : Local reference subjects underwent dark-adapted (DA) and light-adapted (LA) ERG testing according to the ISCEV (International Society for Clinical Electrophysiology of Vision) Standard, using silver threads in the lower fornix, gold foils, and skin electrodes. Comparison analysis was performed to determine whether reference data was transferable between electrode types, directly or with adjustment. A linear model, fitted to the electrode comparison data (n=52), was used to transform local gold foil ERG reference data for inclusion in the reference sample (n=156). Silver thread ERG reference data from a second center underwent verification for inclusion in the reference sample (n=212). The combined sample of 420 reference individuals (one eye per subject) was used to derive age-adjusted reference limits for timing and amplitude of the main DA 0.01, DA 3, DA 10, LA 30Hz and LA 3 ERG components.

Results : There was no significant difference in ERG amplitude or peak time between the centers (p>0.05). Silver thread and gold foil ERG amplitudes and peak times were correlated (r² ranged from 0.68 - 0.98). Bland-Altman analysis revealed no clinically significant bias in gold foil and silver thread ERG peak time (≤1.5ms for all ERG components), with LA 30Hz peak time showing the highest agreement (bias: -0.2ms, 95% limits of agreement (LOA): -1.1 to 0.7ms, ‘silver thread - gold foil’). There was a clinically significant amplitude difference between electrode types: silver thread ERGs were 55 – 65% the amplitude of gold foil ERGs (LOA ranged from 29 – 90%) and skin ERGs were around 35% the amplitude of silver thread ERGs (LOA ranged from 18 – 54%). Pooling of reference data provided a sufficient sample covering 8 decades, from which age-adjusted reference limits were calculated.

Conclusions : Reference ERG data recorded according to the ISCEV Standard may be transferred from one electrode type to another and between centers, following verification. The study highlights the potential of developing large and robust ERG reference ranges, pertinent to standardization, clinical management, and multi-center studies.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.