Coloboma of the optic nerve is a rare, congenital anomaly, especially when it is unassociated with defects of the surrounding choroid. Vossius1 found this condition present in only three of twelve thousand persons examined. Caspar,2 in 1887, collected reports of twenty cases, and Saemisch and his co-workers,3 in 1891, increased this number to forty-eight. Coats,4 in 1907, added six more cases, in all of which he had made microscopic studies and verified the diagnosis.
In 1912, Crampton,5 in an extensive review of the literature, could find only twenty-one cases of true coloboma of the optic nerve, and these occurred in sixteen patients. Included in this group were the six unequivocal cases of Coats,4 together with three cases of his own. Since that time other cases have been reported. Calhoun,6 in 1930, reported a bilateral case associated with holes in the disk and