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anomalous trichromatism anomalous trichromatic vision.
A form of defective colour vision in which three primary colours are required for colour matching, but the proportion of each primary is not the same as those required by a normal trichromat. There are three types of anomalous trichromatism; deuteranomaly, protanomaly and tritanomaly. Syn. anomalous trichromacy; anomalous trichromatic vision. See primary colours; defective colour vision.