ISCEV extended protocol for derivation and analysis of the strong flash rod-isolated ERG a-wave

Mitchell Brigell,Brett G. Jeffrey,Omar A. Mahroo,Radouil Tzekov

doi:10.1007/s10633-019-09740-4

Abstract

The International Society for the Clinical Electrophysiology of Vision (ISCEV) standard for full-field electroretinography (ERG) describes a minimum set of tests, but encourages the use of additional protocols for clinical ERG testing. This extended protocol describes recording methods and derivations that will allow analysis of rod-driven components of the dark-adapted (DA) strong flash ERG a-wave, more closely related to rod phototransduction than ISCEV standard DA ERGs. The method involves recording ERGs to a flash strength equivalent to 30 cd s m2 under conditions of dark adaptation and additionally to the same stimulus following light adaptation (LA) and in the presence of a standard photopic background luminance of 30 cd m−2. The isolated rod-driven ERG a-wave is derived by subtracting the LA response from the DA ERG. The method is likely to be of value in the characterization of retinal disorders which affect rod quantal catch, diseases that affect the dynamics of any component of the activation phase of rod phototransduction, or those affecting total numbers of rod photoreceptors.

Highlights

The International Society for Clinical Electrophysiology of Vision (ISCEV) standard for full-field electroretinography (ERG) describes a minimum set of tests [1], but encourages the use of additional protocols for clinical ERG testing. This extended protocol describes extracting ERG components related to rod phototransduction from the a-wave response to a strong flash
The normal human dark-adapted ERG to a strong brief flash is a mixed response with both rod- and conemediated contributions
The cone-driven contribution is not negligible; in diseases in which rod responses are selectively attenuated, the cone system is likely to contribute proportionately more to the response, making accurate assessment of rod photoreceptor signals more challenging

Summary

Introduction

The International Society for Clinical Electrophysiology of Vision (ISCEV) standard for full-field electroretinography (ERG) describes a minimum set of tests [1], but encourages the use of additional protocols for clinical ERG testing. ERGs to a flash strength equivalent to 30 cd s m2 under conditions of dark adaptation and to the same stimulus following light adaptation (LA) and in the presence of a standard photopic background luminance of 30 cd m-2. This extended protocol describes extracting ERG components related to rod phototransduction from the a-wave response to a strong flash.

Results

Conclusion