Factors that cause variability in chromatic sensitivity in normal colour vision and in congenital deficiency

Le résumé fourni par la source

The inherent variability in chromatic sensitivity was examined in relation to Rayleigh matches and measurements of chromatic detection thresholds in ∼ 330 normal trichromats and ∼ 260 subjects with red/green colour deficiency. Nagel anomaloscope matches were also modeled to predict how the wavelength of peak sensitivity of cone photo-pigments, the effective photo-pigment optical density and the noise amplitude in the red-green colour channel affect the midpoint and the matching range. The model predicts the variability in Nagel match parameters observed in normal trichromats and also in colour deficient observers. The existence of variant L and M cone pigment genes within normal trichromats and the consequent variation in peak wavelength separation remains largely undetected both in Rayleigh match parameters and in colour detection thresholds. The midpoint of the match remains within the normal range when both L and M cone pigment peaks shift symmetrically towards each other without altering the mid wavelength point. The size of the matching range also remains relatively unaffected for dl max separations [[gt]] 15nm ( m = 3.98, s = 1.38, min, max: 1, 9). These observations suggest that subjects with variant L and M cone pigments will generally produce “normal” Rayleigh match parameters, but may exhibit reduced chromatic sensitivity under more natural viewing conditions. The few, extreme L and M gene variant pairs that result in dl max values of less than 15nm, yield measurable loss of chromatic sensitivity. The model also predicts the “normal” Nagel matches measured in subjects with reduced chromatic sensitivity (typical of minimum deuteranomaly) that rely on extreme L and M hybrid genes.

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