The Interpretation of Multifocal Binary Kernels

The interpretation of binary kernels derived by means of the mulifocal ERG has frequently been the source of confusion and controversy. The aim of this paper is to provide an intuitive understanding of the concept of kernels and to demonstrate with models and examples, the relationship between the kernels and individual responses. The sample data used to illustrate the various aspects of the technique were derived and analyzed by means of the multifocal VERIS instrument using bipolar Burian-Allen contact lens electrodes. From the kernel data, response waveforms are synthesized that can be readily compared with those obtained with conventional flash, double flash and multi-flash ERG techniques. From the kernels of a single multifocal record, waveforms are synthesized that describe responses at various times after a preceding focal flash. It is shown that the observed adaptive changes in the waveforms depend not only on the flash interval but also on retinal eccentricity. Features on the response waveform exhibit independent adaptive behavior suggesting that they originate from different retinal sources. On one hand, the examples presented here illustrate the rich information on retinal dynamics contained in the kernels. On the other hand, they demonstrate how the interpretation of multifocal data can be facilitated when the kernel series is transformed into representations with more direct physiological appeal.