The amplitude of the c wave in the human ERG as a function of the luminous energy of the stimulus.

Variation of the stimulus intensity and duration over a wide range causes a change in amplitude of the c wave. If the energy of the applied stimulus is kept constant, however, stimuli of 0.05-4 s duration effected c waves that were nearly equal in amplitude. As patients consider shorter stimuli with higher intensities to be more comfortable in ERG recording, stimuli of a duration of 2-4 s seem most appropriate for clinical testing.