Aplasia of the optic nerve and disk.

To clarify the nature of aplasia of the optic nerve and disk, a rare congenital anomaly defined as absence of the optic nerve and disk, retinal ganglion cells, and retinal blood vessels, we evaluated all the cases with this designation in the files. Thirteen cases demonstrated that optic nerve aplasia typically occurs uniocularly in an otherwise healthy person. There was no sexual or racial predilection, or any evidence of an inherited factor. We believe typical aplasia of the optic nerve results from abnormal invagination of the ventral fissure and that the multiple associated ocular anomalies may also be attributed in part to this same mechanism. Two cases were atypical: they were bilateral, there was an associated hydrocephalus in one case and a possible familial history in the other, they apparently had a different pathogenesis from the typical cases, and possibly represent an extreme form of hypoplasia of the optic nerve.