FLICKER CONE ELECTRORETINOGRAM IN DICHROMATS AND TRICHROMATS

To measure cone signal strengths in the flicker electroretinogram (ERG ) of dichromats and trichromats, we developed a set of flickering stim uli (30 Hz), which excite the middle-wavelength-sensitive (M-) and lon g-wavelength-sensitive (L-) cones independently. ERG responses to eigh t different ratios of L- to M-cone contrasts were recorded from each s ubject. The short-wavelength-sensitive (S-) cone contrast was 0% in al l measurements. The recordings were Fourier analyzed to determine the amplitude of the fundamental component. ERG threshold values for each subject resulted in ellipses when plotted in an L-/M-cone contrast spa ce. As expected, the orientations of the threshold ellipses of the pro tanopes (N = 2) were parallel to the L-cone axis, whereas those of the deuteranopes (N = 2) were parallel to the M-cone axis. For the trichr omats (N = 5), there was considerable interindividual variation in ell ipse orientation. (C) 1998 Elsevier Science Ltd. All rights reserved.