Further studies supporting the identity of congenital tritanopia and hereditary dominant optic atrophy.

Dominant inherited optic atrophy is usually a stationary disorder with typical findings of temporal optic nerve pallor, abnormal distance acuity, minimal visual-field defects, and characteristic color confusions in the blue-green region of the spectrum. Variability in the severity of these abnormalities is common, even within the same family. In patients with minimal disease, distance acuity may be close to normal and optic pallor may be so subtle that a definitive diagnosis cannot be made unless other obviously affected members of a family are seen. Our studies indicate that patients with dominantly inherited optic atrophy have similar color vision to that previously reported for subjects with congenital tritan defects. In fact, the almost identical color-vision profiles and pattern of inheritance of the two conditions lead us to question the existence of congenital tritan defect as an independent entity. Criteria are suggested for distinguishing the two conditions. It is emphasized that the utmost care should be taken to rule out dominant optic atrophy in future subjects in whom congenital tritanopia is suspected, both because of the strikingly similar characteristics of the two conditions, if these are indeed separate entities, and because the diagnosis of hereditary dominant atrophy may be easily missed.