distance between the superior aspect of the optic canal
and the base of the metoptic canal,
Optic strut connects the body of sphenoid to the inferomedial aspect of base of anterior clinoid process and is removed during anterior clinoidectomy and optic canal
Indirect TON may be treated with various doses of steroids, or alternatively surgical optic canal
decompression can be performed (2,4,8,10).
At present, most scholars hold that the neurological symptoms are due to the thickening of the bone plate at the bottom of the skull and stenosis or occlusion of channels in which cranial nerves, spinal cord, and major blood vessels run, including the optic nerve compression caused by the optic canal
stenosis. The mechanism of optic nerve damage is still not fully understood.
Megadose steroids should be withheld if more than 8 hours has elapsed since trauma, while optic canal
decompression plays no role if vision loss happened at the time of injury and not later, in addition to risk of intraoperative injury of optic nerve [1, 13].
Mizushima et al., "Intracranial penetrating injuries via the optic canal
," American Journal of Neuroradiology, vol.
The recommended imaging to analyze the sphenoid sinus and its surrounding structures is the CT paranasal sinuses including axial, coronal, sagittal, and sagittal oblique (parallel to the optic canal
 reported that one case receiving decompression of optic canal
and SOF regained visual perception successfully.
A negative correlation between drusen diameter and RNFL thickness as well as greater RNFL loss in drusen located in the optic canal
have been demonstrated.
A soft-tissue enhancing mass extended into the optic canal
, causing compression and medial displacement of the right optic nerve (Figure 2A).
The optic nerve emerges from behind the eyeball and travels posteriorly towards the back of the orbit to enter the optic canal
. Along its path it can become compressed, inflamed, ischaemic or mechanically stretched by the abnormally enlarged surrounding extraocular muscles and orbital tissues leading to dysthyroid optic neuropathy (DON).
The infraorbital foramen was the landmark from which the distance between the following bony structures were examined; Nasion (NAS), Zygomatico maxillary suture (ZMS), Anterior nasal spine (ANS), and the distance between the inferior orbital rim (IOR) to optic canal
(OC), infraorbital foramen (IOF), inferior & superior orbital fissure (IF & SF) (Figure 1).