OBJECTIVE SPECIFICATION OF TRITANOPIC CONFUSION LINES USING VISUAL-EVOKED POTENTIALS

The minimum distinct border (MDB) between different isoluminant hues o f a bipartite field was set subjectively by adjustment and then accord ing to a 3-point rating allowing determination of the S-cone specific (tritanopic) axis. This rating was compared with visual evoked potenti als (VEPs) generated by coarse, isoluminant gratings, modulated along the same chromatic axes. Psychophysically determined tritanopic gratin gs elicited monophasic onset VEPs with the longest latency for each su bject. Departure from this axis produced additional earlier negative c omponents (reflecting additional response mechanisms). Colour-selectiv e VEPs can, therefore, objectively specify tritanopic confusion lines with a comparable degree of accuracy to MDB judgements. (C) 1998 Elsev ier Science Ltd. All rights reserved.