The use of non-linear analysis of the primate ERG to detect retinal dysfunction

Abstract

Serial ERG's were recorded from rhesus monkey eyes after a standard posterior penetrating ocular injury and simulated vitreous hemorrhage caused by the injection of 0·5 ml of autologous blood. As reported previously, this procedure resulted in a progressive reduction, to virtual extinction, of the ERG, followed by a remarkable recovery over a period of 8–10 weeks. In this study, the a- and b-waves of the flash evoked ERG were compared with similar features of the response to a rapid random flash stimulus. The first order kernel (KF) like the flash response underwent progressive changes, during the 12 week recovery period, in amplitude and waveform. Its a-wave, like the flash a-wave was substantially recovered by 126 days. Its b-wave, however, showed much less recovery than the flash b-wave. This b-wave depression in the KF reflects a defect in rapid adaptation of the retina. It is conveniently evaluated as the ratio of first to second order kernels, (-KS/KF), called the adaptation index. This measure was abnormal in the post-operative retina for the b-wave but not the a-wave permitting the conclusion that the defect is postsynaptic to the receptors.