Optic Nerve-Pettern Electroretinogram

Recently, the electroretinogram (ERG) recorded in response to patterned stimuli (PERG) were shown to be sensitive to pattern contrast and spatial frequency unlike the diffuse flash ERG. These findings coupled with experimental animal work suggest that the PERG reflects functioning of the ganglion cells which are the cell bodies of the axon of the optic nerve. Subjects with optic neuropathies should be ideally suited to this hypothesis. PERG, flash ERG, and visual evoked potentials (VEP) were studied in cases with unilateral optic nerve diseases secondary to tumors or optic neuritis. The PERG was absent in the affected eyes with poor acuity (less than 20/60) while the flash ERG was normal. A second group with acuity better than 20/40 showed reductions in the PERG amplitude of the affected compared to the normal eye. These interocular differences were especially marked when pattern contrast was reduced. Such results underscore the diagnostic value of the PERG in detecting mildly affected cases of optic nerve disease. These findings provide additional evidence regarding the ganglion cell origin of the PERG

The Neurophysiology of Vision

Electrophyslologlcal testing Is often an Important adjunct to the neuro-ophthalmlc examination In a patient with visual loss. This paper reviews techniques and dinlcal applications of electroretinography and visual evoked potential (YEP) recording