Abstract

A new recording technique for the electroretinogram is used to study the distribution of pattern electroretinogram components within the central 23° of the visual field. The main focus is on the first slice of the second order binary kernel (response to pattern reversal between consecutive stimulus frames). Its topography shows great nasal/temporal asymmetry in amplitude as well as wave form within the central 15°. The asymmetry is not seen in the local luminance response and there is no known anatomical or histological correlate. A two component hypothesis provides a plausible explanation. Both components have a relatively symmetrical distribution in amplitude and wave shape. However, the second component shows increased latencies that correlate with the length of the fiber bundle to the optic nerve head. This finding suggests a signal source in the area where myelination begins. The latency shifts are attributed to propagation delays in the unmyelinated nerve fiber layer. This hypothesis finds further support in the topographies of the two components. While the first component can be attributed to nonlinearities of the luminance response in the outer retinal layers, the second component shows further enhancement of the central response due to the increase in the ganglion cell to receptor ratio.

© 1990 Optical Society of America