The optic nerve, also known as cranial nerve II, transmits visual information from the retina to the brain. Derived from the embryonic retinal ganglion cell, a diverticulum located in the diencephalon, the optic nerve does not regenerate after transection.
The optic nerve may be divided into 4 segments: intraocular (1 mm in length), intraorbital (25–30 mm), intracanalicular (10 mm), and intracranial (10 mm).
AC: anterior clinoid process; ICA: internal carotid artery; LT: lamina terminalis; ON: optic nerve; OlN; olfactory nerve; SW: sphenoid wing; TS: tuberculum sellae; A1: A1 segment of the Anterior Cerebral Artery; A2: A2 segment of the Anterior Cerebral Artery; M1: M1 segment of the Middle Cerebral Artery
see Optic nerve injury.
In cases where the tumour is confined to the optic nerves, they can safely be referred to as optic nerve gliomas. Often optic nerve gliomas are either centred on or extend to involve the chiasm and optic radiations. In such cases, they are difficult to distinguish from hypothalamic gliomas and such a distinction is in most instances artificial. In such more posterior cases the term hypothalamic-optochiasmatic glioma is perhaps more accurate although it certainly does not roll off the tongue.