THE OFF RESPONSE OF THE HUMAN ELECTRORETINOGRAM DOES NOT CONTRIBUTE TO THE BRIEF FLASH B-WAVE

It has been assumed that the 'ON' and 'OFF' responses of the human ele ctroretinogram (ERG) interact to produce a single waveform when brief flashes are used. To test this assumption, we examined the separate ef fects of stimulus intensity, the level of retinal illuminance and stim ulus duration on the ERG. Both 'ON' and'OFF' response amplitude decrea sed as stimulus intensity was decreased and as the level of retinal il lumination was reduced. When stimulus duration was reduced, the amplit ude of the 'OFF' response decreased; however, the amplitude of the 'ON ' response increased. Summing of the 'ON' and 'OFF' response waveforms could not account for the increased amplitude in response to brief st imuli or for the changes in ERG wave shape. These results indicate tha t there is not a significant corneally recordable 'OFF' response elici ted by brief stimuli, such as those commonly used to record the flash ERG.