The clinical picture of hereditary dominant optic atrophy is described and the particular importance of the concomitant tritan dyschromatopsia is stressed. Most cases of tritanopia are acquired, congenital ones are rare. Wright has studied 17 tritanopes - the greatest series ever reported. A full analysis of colour vision is given, but no detailed information about other visual functions and the condition of the fundi. As single members of families affected by cominantly inherited optic atrophy show typical tritanopia, a visual acuity of 6/8 and hardly any pallor of their disks, it is possible that such isolated cases are regarded wrongly as congenital tritanopes.