ABSTRACT
This chapter discusses the aim and the background of the ocular electrophysiology. It examines three components to electrodiagnostic testing: electroretinography (ERG), electrooculography (EOG), and visual evoked potential (VEP). ERG demonstrates electrical potential at the retina during stimulation. Corneal or lid electrodes are used to detect changes in electrical potential during and after stimulation of the neurosensory retina. EOG is used to establish retinal-pigment-epithelium (RPE) function. RPE function is calculated by dividing the light peak by the dark trough – giving the Arden ratio. The normal Arden ratio is greater than 1.8; diseases primarily affecting the RPE, such as Best’s disease, demonstrate a reduced Arden ratio. VEP testing interrogates the entire visual pathway, from the retina to the visual cortex, by using scalp-based electrodes. Thus, stimulation of the visual cortex is detected, and comparison of conduction times as well as the amplitudes of depolarisation form the VEP trace.
