ISCEV extended protocol for the photopic On-Off ERG

Abstract

The International Society for Clinical Electrophysiology of Vision (ISCEV) standard for full-field electroretinography (ERG) describes a minimum procedure, but encourages more extensive testing. This ISCEV extended protocol describes an extension to the ERG standard, namely the photopic On-Off ERG, and outlines common clinical applications. A light stimulus duration of 150-200 ms is used in the presence of a rod-suppressing background to elicit cone-driven On- and Off-system ERG components. The On-response occurs after the stimulus onset and has a negative a-wave and positive b-wave. The Off d-wave is a positive component evoked by stimulus offset. Common diagnoses that may benefit from additional photopic On-Off ERG testing include retinal dystrophies and retinal disorders that cause dysfunction at a level that is post-phototransduction or post-receptoral. On-Off ERGs assess the relative involvement of On- and Off-systems and may be of use in the diagnosis of disorders such as complete and incomplete congenital stationary night blindness (complete and incomplete CSNB), melanoma-associated retinopathy, and some forms of autoimmune retinopathy. The photopic On-Off ERGs may also be useful in X-linked retinoschisis, Batten disease, Duchenne muscular dystrophy, spinocerebellar degeneration, quinine toxicity, and other retinal disorders.

Keywords: Bipolar cells; Clinical standards; Electroretinogram (ERG); Full-field ERG; International Society of Clinical Electrophysiology of Vision (ISCEV); Long-duration ERG; On–Off ERG; Retinal dystrophy; Retinopathy.

Fig. 1

Diagram of the three main components of the photopic On–Off ERG and their measurement. Stimulus duration is indicated at the bottom of the figure; red (vertical) arrows indicate amplitude measurement, blue (horizontal) arrows indicate peak time measurement. Two traces are superimposed to demonstrate reproducibility