THE c‐WAVE OF THE HUMAN D.C. REGISTERED ERG. II. CYCLIC VARIATIONS OF THE c‐WAVE AMPLITUDE

Abstract

The c ‐wave of the human ERG was studied with a new d.c. technique. The c ‐wave amplitude showed cyclic variations with a frequency of about 2/hour when repeatedly recorded. The average amplitude difference between the peak and the trough of the first oscillation was about 150 μ V. With a stimulus frequency of 2/min the changes resembled damped oscillations. After 1 hour they were quite small. With a stimulus frequency of 0.5/min the oscillations were not clearly damped within 1 hour. There was also evidence of a much slower change upon which the 2/hour oscillations seemed to be superimposed. These findings will be of importance if a clinical routine procedure for registrations of the c ‐wave is to be developed.