A new method of cone electroretinography: the rapid random flash response.

A new procedure is described for cone electroretinography using a cross-correlation method of signal processing to give the response to flash stimuli which occur at randomly timed intervals. The output waveform is different than the usual repetitive flicker response, and can be presented on any desired time base. An unfamiliar aspect of this process is that most of the random time intervals between consecutive stimuli are shorter in duration than the output waveform. For the parameters described, the output waveform gives the response to approximately 1,640 stimuli in 65.5 sec., with a signal-to-noise ratio which is higher than that obtained when conventional averaging techniques are used over similar time periods. This allows more precise and statistically significant estimates to be made of the time and amplitude parameters of the cone response. Normal values are given for implicit (delay) time and amplitude, and examples are provided for comparison of the random flash response and conventional average electroretinograms (ERG's) in normal subjects and patients with retinal degeneration.