ISCEV extended protocol for the S-cone ERG

Ido Perlman,Graham E Holder,Mineo Kondo,Anthony G Robson,Enid Chelva

doi:10.1007/s10633-019-09730-6

Abstract

The International Society for Clinical Electrophysiology of Vision (ISCEV) standard for full-field electroretinography (ERG) describes a minimum procedure for testing generalized retinal function but encourages more extensive testing. This extended protocol describes a method of assessing the function of the short-wavelength-sensitive cone (S-cone) retinal pathway, using a short-wavelength flash superimposed on a background that saturates the rods and adapts the L/M-cones to elicit a response, known as the S-cone ERG. Stimulus parameters such as the strength and luminance of the flash and background, respectively, and their spectral and temporal characteristics are specified. As a complement to the ISCEV standard, testing the S-cone ERG enables further characterization of light-adapted retinal function and may refine diagnosis of some retinal disorders. Typical applications are described including use in the diagnosis of rod monochromacy and S-cone monochromacy, identification and investigation of cone On-bipolar cell dysfunction and use of the technique to confirm the diagnosis of enhanced S-cone syndrome.

Highlights

The International Society for Clinical Electrophysiology of Vision (ISCEV) standard for full-field electroretinography (ERG) describes a minimum procedure for testing generalized retinal function but encourages more extensive testing [1]. This extended protocol describes a method of assessing the function of the short-wavelength-sensitive cone (S-cone) retinal pathway, using a short-wavelength flash superimposed on a background light to elicit a response, known as the S-cone ERG
The standard LA ERGs are normally dominated by responses driven by the long-wavelength-sensitive cones (L-cones) and medium-wavelength-sensitive cones (M-cones)
There are far fewer short-wavelength-sensitive cones (S-cones) than L/M-cones, and their summed responses to light are of smaller amplitude and slower kinetics

Summary

Introduction

The International Society for Clinical Electrophysiology of Vision (ISCEV) standard for full-field electroretinography (ERG) describes a minimum procedure for testing generalized retinal function but encourages more extensive testing [1] This extended protocol describes a method of assessing the function of the short-wavelength-sensitive cone (S-cone) retinal pathway, using a short-wavelength flash superimposed on a background light to elicit a response, known as the S-cone ERG. A more detailed knowledge of the phenotype may refine the diagnosis and facilitate mutational screening It can confirm the origins of the recorded signals in enhanced S-cone syndrome (ESCS) consequent upon mutation in NR2E3 gene after the pathognomonic features have been revealed with conventional ISCEV standard ERG testing [5, 6]. Light sources with wavelength shorter than 440 nm may not have sufficient strength to elicit a reliable S-cone ERG because the S-cone ERG action spectrum peaks at 450 nm [3]

Background wavelength luminance

Compliance with ethical standards