[Workshop on electroretinography and visual evoked potentials]

Abstract

Studies of vision using electrophysiological techniques are tests which record functional alterations in very early phases of a disease. Full field flash ERG evaluates the integrity of the cones, rods and bipolar cells. It is obtained by photopsic stimulation with Ganzfeld and contact lens corneal electrodes or, alternatively, gold leaf or anchor electrodes. Five responses must be obtained: that of the rods, a maximum, oscillatory potentials, that of the cones and a flicker response. Pattern ERG is a response of the ganglionic cells, which is obtained by pattern reversal morphoscopic stimulation, with a bandwidth between 1 and 60 Hz. The fundamental waves (0.5 5 mV) are P50 (luminance) and N95 (pattern specific). This is of great value in the early diagnosis of glaucoma. VEP are electrical fields that are recorded in the calcarine cortex. They give information about alterations in the optic nerve, chiasm, radiations and cortex. Pattern VEP is obtained with a visual angle of between 13 and 14 . The fundamental wave P100 is evaluated according to its latency and amplitude, and by comparing it with a healthy eye. Flash VEP is only used on patients who do not collaborate or who present an opacity of media.