Electroretinography

The electroretinogram (ERG) is a mass electrical response from the retina, evoked by a brief flash of light. ERG recording is done using an active electrode (a contact lens in contact with bulbar conjunctiva) and a reference electrode (at the outer canthus); the active electrode can also be a gold foil electrode or HK-loop electrode. There are three types of ERG: the full-field (Ganzfeld) ERG, the multifocal ERG, and the pattern ERG.