The optic canal, in particular its intracranial end, represents a "locus minoris resistentiae" for optic nerve compression in a variety of pathologic conditions. The intracranial optic nerve shares the limited space within this narrow passage with the carotid and ophthalmic artery, all being surrounded by bone and rigid dura. Any pathological condition going along with an increase of soft tissue volume, such as in optic nerve sheath tumors, parasellar neoplasms, dolichoectasia of the carotid and/ or ophthalmic artery, hematomas, etc., or reduction of the lumen of the bony optic canal by...