The OS serves as an effective landmark in CTA source images for distinguishing between intradural and extradural paraclinoid aneurysms. The distal dural ring (DDR) is supposed to be located 2 mm above the base of the OS in axial planes 1).
optic canal (OC)
optic strut (OS)
superior orbital fissure (SOF)
The optic canal (OC) opens into the superomedial corner of the orbital apex at the junction of the roof and medial wall. It is separated from the superior orbital fissure (SOF) by the optic strut (OS), a bridge of bone, also referred to as the posterior root of the lesser wing, which extends from the lower margin of the base of the anterior clinoid process to the sphenoid body.
From an intracranial view we can see how the optic strut (OS) is a bony projection of the anterior clinoid process (AC) to the sphenoid bone.
The optic strut is a triangle shaped area bounded by the ICA, the optic nerve and the superior orbital fissure (SOF).