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Jesson Martin, Adam Dubis, Joseph Carroll, John Krauskopf; Estimation of L: M Cone Ratio from ERG, Adaptive Optics, and Color Naming Methods. Journal of Vision 2007;7(15):81. doi: 10.1167/7.15.81.
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© ARVO (1962-2015); The Authors (2016-present)
The relative proportion of L and M cones is remarkably variable among humans. Here we present estimates of L: M cone ratios of 8 male subjects using a new method based on the color appearance of small spots of light to which L and M cones have been found to be equally sensitive (Iso_LM stimuli). The Iso_LM stimuli were determined by application of the Stiles two-color increment threshold procedure. The new estimates of the L:M ratios are compared with ones previously made on these subjects using flicker photometric ERG and adaptive optics. In addition, we obtained measurements of unique yellow and genetically characterized each subject's L and M cone pigments. We find a significant difference in Iso_LM between individuals with different L photopigment variants, consistent with it being determined simply by the pigment sensitivity; however the absolute position of Iso_LM deviated from that predicted from a simple model of photopigment sensitivity, suggesting the presence of a gain within the M-cone pathway. Further analysis reveals limited correlation between the ERG/AO estimates and those derived from the psychophysical technique, with the psychophysical technique consistently underestimating the L: M ratio derived from the ERG/AO. However, there does appear to be significant variability between subjects with all three techniques, consistent with a shared physiological origin.
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