<prompt> The optic nerve is a tract of the diencephalon that is not completely myelinated until5 years after bih2 years after bih1 year after bih3 months after bih  <response>: 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. 