Pathology of the X-wave of the Human Electroretinogram*

MOTOKAWA and Mita (1942) discovered a subsidiary positive deflection preceding the b-wave of the ERG in a moderately light-adapted human eye. They called it "x-wave", but gave no interpretation of it. Independently of these Japanese authors, Adrian (1945) rediscovered the phenomenon. He established that the b-wave (which he called "scotopic response") is absent in red light and in a state of light adaptation, and that it can be isolated in blue light; it is augmented considerably by dark adaptation. On the other hand, the x-wave (called " photopic response ") is absent in blue light and can be isolated in red light; it should not increase by dark adaptation. The x-wave is more rapid than the b-wave so that both may be recognized together in orange light. Adrian (1946) showed that the x-wave may be demonstrated in animals with a rich cone-population (monkey; pigeon) and not in animals with few or no cones (cat, rabbit, guinea-pig). Amongst the few contributions concerning the x-wave which have appeared in recent years, those of Schubert and Bornschein (1952), Armington (1952), Armington and Schwab (1954), Armington and Thiede (1954), and Auerbach and Burian (1955) are the most important. Schubert and Bornschein showed that, whereas the culmination time of the b-wave increases with the wave length of the stimulus, that of the x-wave remains constant and equal to 50-70 millisec.; the latency time is equal to 25-30 millisec. Armington (1952) demonstrated that the x-wave is augmented by dark adaptation, but that the maximum amplitude is already reached after 1 minute; its spectral sensitivity does not correspond to the subjective scotopic or photopic curves, but has a maximum for a wave length of 630 mix. Armington and Thiede (1954) showed that either the x-wave or the b-wave may be selectively reduced in amplitude if the eye is adapted to light of which one electrical component or the other possesses greater sensitivity. Auerbach and Burian (1955) emphasized the relationship