Retinitis pigmentosa vs normal (ERG)

The ERG is recorded at the cornea and referenced to the back of the eye. It is a graphic representation of the change in voltage as a function of time following the introduction of a stroboscopic flash presented in a Ganzfield (uniform featureless visual field). Clinical electroretinography is usually done in accordance with standards set forth by the International Society for Clinical Electrophysiology of Vision (ISCEV). The top three ERG records in this figure are normal. 1-R is produced by a bright white flash on a dark field and is both photopic and scotopic in origin. 2-R is produced by the same bright field on a lighted background and is photopic in origin. 3-R is a dim flash on a dark background in a dark-adapted eye. It is purely scotopic in origin. Record 4-R is the response to a scotopic stimulus in a patient with retinitis pigmentosa. (Contributed by Dr. James Walters.)