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Electroretinography, is used to measure the electrical responses of various cell types in the retina, including the light-sensitive cells (rods and cones) and the ganglion cells. Electrodes are placed on the cornea and the skin near the eye. During a recording, the patient is watching a standardized stimulus and the resulting signal is interpreted in terms of its amplitude (voltage) and time course. Stimuli include flashes (flash ERG) and reversing checkerboard patterns (pattern ERG). Applications are predominantly in ophthalmology, where the electroretinogram (ERG) is used for the diagnosis of various retinal diseases:[1]

The multifocal ERG is used to record separate responses for different retinal locations.

Electroretinograms can be broken down into three components: an initial a-wave, caused by extracellular ionic currents generated by photoreceptors during phototransduction, the b-wave, which corresponds to bipolar cell activity, and the later c-wave, which is generated by the retinal pigment epithelium and Müller cells. Depending on the species the ERG is taken from, the c-wave may be positive, negative, or absent in part or in whole.[2]


  1. Electroretinography, U.S. National Library of Medicine, 11 april 2005 (accessed 19 January,2007)
  2. Clinical Electrophysiology,Donnell Creel, date unknown (accessed 19 January,2007)

See also