Electrophysiological testing allows objective assessment of retinal function. By changing the nature of
the stimulus presented to the patient and the adaptive state of the eye (light or dark adapted) responses from
different retinal cell types and layers can be obtained. The primary tests used in the evaluation of inherited retinal
disease are the full-field electroretinogram (ERG), the pattern electroretinogram (PERG) and the electrooculogram
(EOG), obtained following the International Standards for Clinical Electrophysiology in Vision
(ISCEV) as well as the more recent techniques multi-focal electroretinogram (mfERG), ON/OFF ERG and s-cone
ERG. Electrophysiological testing is useful for both the diagnosis and follow-up of patients with inherited retinal
disease and is indicated when (1) the retina is morphologically “normal” but the patient is symptomatic, (2) the
fundal appearance may not reflect the severity or nature of the disorder; (3) an accurate diagnosis is required or
(4) prognostic information is required for the management of the patient. This chapter provides the basics of the
electrophysiological techniques that can be used, suggests the pertinent tests to make the diagnosis and reviews
the typical electrophysiological findings in a range of the more commonly encountered inherited retinal diseases.
Keywords: Electrophysiology, electroretinogram, pattern electroretinogram, electro-oculogram, visual evoked
potentials, ERG, PERG, EOG, VEP, International Standards for Clinical Electrophysiology in Vision, ISCEV, onresponse,
off-response, retina, optic nerve, eye, macula, retinal pigment epithelium, RPE, photoreceptor cell, bipolar
cell, amacrine cell, gangion cell layer, horizontal cell, electrodiagnostics, a-wave, b-wave, P50, N95, dark
adaptation, cone, rod, s-cone, Arden index, multifocal ERG, photopic, scotopic, inherited retinal disease, retinitis
pigmentosa, RP, cone-rod dystrophy, cone dystrophy, pattern dystrophy, PD, adult vitrelliform macular dystrophy,
AVMD, Best disease, Stargardt disease, fundus flavimaculatus, x-linked retinoschisis, retinoschisis, Leber
congenital amaurosis, LCA, maternally inherited diabetes and deafness, MIDD, choroideremia, ESCS, Enhanced Scone
syndrome, Congenital stationary night blindness, CSNB, carrier, fundus albipunctatus, Oguchi disease, Batten
disease, macular dystrophy, Bull’s eye.
