The axons of the optic nerve are not completely myelinated until 3 months after bih. Myelinated axons are normally not found in the retina. The optic nerve is not a true peripheral nerve but a tract of the diencephalon; when severed, the optic nerve does not regenerate. Myelination in the central nervous system (CNS) is accomplished by oligodendrocytes; oligodendrocytes are not found in the retina.