Abstract

The electroretinogram (ERG) is the mass electrical response of the retina to light and is affected by a wide variety of diseases. Because there are many retinal cell types contributing to the electrical response, dissection of the locus of disease-induced abnormalities is qualitative at best. We are using high temporal frequencies to minimize the contributions of rods and non-neural retinal cells to the ERG response. We Fourier-analyze the ERG responses to light modulated by either a sinusoidal or complex temporal waveform and use the amplitude of the linearand nonlinear components of the response to measure early visual processing. For instance, analysis of the beat amplitude in a two-sine-wave technique reveals a mechanism, probably the photoreceptors, that is low-pass with a 3 dB point at 50 Hz and a high-frequency slope of 4.0 on a log-log plot. Analysis of second- and higher- order nonlinear responses reveals a similar high frequency slope but a complex dependence of response amplitude on frequency. The data are compatible with generation by an essential nonlinearity, possibly a nonlinear gain-control mechanism with a temporal delay. We will illustrate the clinical utility of our approach with data from patients with either glaucoma or central retinal vein occlusions.

© 1990 Optical Society of America