C-wave versus electrooculogram in diseases of the retinal pigment epithelium

The c-wave and the electrooculogram (EOG) are retinal potentials predominantly generated by the pigment epithelium. In most diseases both parameters show a parallel decrease in amplitude. However, in patients with dominant drusen, and cone dystrophies, and in clinically nonaffected members of families suffering from vitelliform macula degeneration, the EOG is close to normal whereas the c-wave shows a reduced amplitude. These findings suggest a higher sensitivity of the generators of the c-wave compared with those responsible for the EOG. Thus the direct current electroretinogram provides additional diagnostic information.