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2. a very rare type of dichromatic vision in which there is perception of red and green only, with blue and yellow perceived as an achromatic (gray) band. Some authorities doubt its existence. adj., adj tetartanopsia, adj tetartanop´ic.
tetartanopia(te-tar″tă-nō′pē-ă) [Gr. tetartos, fourth + anopia]
Symmetrical blindness in the same quadrant of each visual field.