The influence of stimulus duration on the human d.c. registered c-wave. A quantitative study.

The c-wave of the human ERG was studied at different stimulus durations with a d.c. technique which permitted stable and reproducible recordings. With increasing stimulus lengths the implicit time increased up to a maximum of about 5.5 s. Also the amplitude of the c-wave rose. However, it was influenced by positive and negative off-effects, seen in most volunteers, and at several stimulus lengths superimposed upon the peak of the c-wave. This fact must be considered when developing a standardized method for measuring the c-wave amplitude proper.