Definition : Visual evoked potential recorders designed for detecting, amplifying and recording the transient change of the electrical potential on or near the surface of the cornea to a reference distal point on the body, following stimulation of the retina by external repetitive stimuli. The results may be displayed as a graphic of the measured voltages vs. time (an electroretinogram); the graph usually shows the a-wave is the first large negative component, followed by the b-wave which is corneal positive and usually larger in amplitude. These recorders typically consist of detachable electrodes usually placed on the cornea (e.g., similar to a contact lens) and on the skin near the eyes; signal amplifiers; filters (to suppress interference); memory (e.g., electronic, optical/magnetic disc); and a display. The recorder may include capabilities to deliver external stimuli (e.g., reversible checkerboard patterns, flashlights) at an appropriate repetitive level to elicit the bioelectric response needed for recording. Electroretinographs are mainly used in studies intended to diagnose acquired and/or inherited retinal diseases, including retinitis pigmentosa. Recorders with additional capabilities for recording the velocity of the short, fast movements of the eyes made during reading and sleep (i.e., saccadic velocity) are also available.
Entry Terms : "ERGs"
UMDC code : 11482