The aim of this study was to obtain information about single cone
class driven activity in the inner and outer retina in humans. We
examined outer retinal activity with the multifocal electroretinogram
(mfERG) and inner retinal activity using multifocal oscillatory
potentials (mfOPs). A standard (black-white) stimulus was used, as well
as stimuli aimed at isolating a single photoreceptor class. The results
of 10 trichromats were compared to those of 2 protanopes and 2
deuteranopes. At both retinal layers we find that trichromats show cone
isolating response amplitudes that reflect the expected number of cones
and that single- gene dichromats have a similar total number of
functioning cones as trichromats. The ratio of the responses of the L-
and M-cones is slightly smaller for the mfOPs than for the mfERGs. The
results indicate that there are major changes in the gain of retinal
signals after the inner plexiform layer.