(a)–(e) Dissections of the right cranial base and orbit. (a) The ophthalmic artery is a branch of the supraclinoid portion of the internal carotid artery, in most cases. This vessel follows the optic nerve in the optic canal and orbit and is the responsible for the supply of orbital structures. (b) The origin of the ophthalmic artery is usually medial to the anterior clinoid process, below the optic nerve. (c) At the optic canal, the artery has passed to a position lateral to nerve. This anatomical fact must be remembered during the opening of the falciform ligament after anterior clinoidectomy, to avoid iatrogenic lesion to this artery. (d) Once inside the orbit, the ophthalmic artery passes, in most cases, above the optic nerve. (e) At the point where the artery crosses the optic nerve, it gives rise to the central retinal artery. Working along the lateral orbital space, it is vital to avoid blind coagulation as ligation of the central retinal artery results in loss of vision.