Localization of Distal Retinal Activity with the Transretinal ERG

Abstract

A wide range of normal human scotopic ERG responses obtained in background adaptation are compactly represented by Rushton H₂ curves; (1) sensitivity and (2) scaling of response size are two separable adaptive properties of both a- and b-waves (Vision Research 18, 1978). A similar H₂ analysis of ERG responses from developing rat retina in background adaptation was done to determine age related changes in a- and b-wave sensitivity and scaling. Correlations of developing ERG to maturing distal retina suggest anatomical sites in photoreceptors and outer plexiform layer which influence sensitivity and scaling of ERG responses. Furthermore, ERG studies of background adaptation in a strain of mutant mouse (pcd) having progressive retinal degeneration which begins in the photoreceptor inner segments have revealed sensitivity and scaling changes which are clearly distinguishable from normal. We have now devised an abbreviated procedure which allows rapid assessment of sensitivity and scaling of human ERG responses in conditions of background adaptation ranging from dark to those which saturate the psychophysical increment threshold. In human retinal diseases localization of the site of early degeneration in rods may become possible through this technique.