Electroretinographic responses of the short-wavelength-sensitive cones.

An electroretinographic response of the human short wavelength (S) cone system can be distinguished from that of the longer wavelength (L or M) cone system by using ganzfeld short-wavelength stimulation at relatively high levels of retinal adaptation. The S cone response has both an a- and b-wave component in its ERG, both of which are slower than those of the L or M cone response at the same level of retinal adaptation. Proof that this is the S cone response is obtained by action spectra and by examination of a sex-linked achromat who is known to have only S cone and rod vision. This approach allows the simultaneous and rapid assessment of both the S and the L or M cone systems in the human retina using conventional electroretinogram (ERG) equipment, ganzfeld blue flashes on a white background, and computer averaging.