Optic nerve (CN II)
The optic nerve is the second cranial nerve which along with the olfactory nerve (CN I) is really an extension of the central nervous system with first sensory bipolar cell body located peripherally in the retina. Their central processes synapse on ganglion cells on the vitreous surface of the retina, and their central processes pass via the optic disc out of the globe and form the optic nerve proper.
The optic nerve travels centrally within the orbit, surrounded by an extension of the dura mater, which allows for direct communication with the subarachnoid space and therefore allows transmission of increased presure from hydrocephalus to manifest as papilloedema. Additionally the dural covering can develop a meningioma.
The optic nerve exits through the tendinous ring and optic canal to enter the middle cranial fossa, and soon join the contralateral optic nerve at the optic chiasm.
