Application of twin flash stimuli for some mascular diseases isolation of local responses by twin flashes

Double flash ERG was examined for patients with visual loss from macular and optic nerve disorders, and the responses were compared. K values (= (B1-B2))/B1 x 100) of the former were larger than normal values when the stimulus intervals were between 200 and 500 mseconds, and abnormality of K values seemed to correspond to the functional impairment of macula. On the other hand, K values of the patients with optic nerve diseases remained in the normal range. These facts indicate that double flash ERG is a very useful method to estimate the cone function clinically, and can be employed as a routine examination for patients with suspected cone dysfunction.