Metoptic canal, duplication of the optic canal and Warwick’s foramen in human orbits.

The region of the optic strut is sometimes traversed by some minor canals whose incidence and general characteristics have never been studied. As such canals could be the route for vessels that could interfere in the surgery of the orbital apex, we undertook a detailed anatomical study on a vast collection of dry skulls. The examination of 943 dry adult skulls and 360 foetal skulls was carried out to precise the anatomy of canals in the optic strut area, their development and relationships with the optic canal. A canal traversing the optic strut was present in 8.54 % of the orbits. Based on diameter, position within the optic strut, and thickness of the bony plate separating it from the optic canal or from the superior orbital fissure, the canals piercing the optic strut were classified into four types, which include the well-known duplication of the optic canal, different aspects of the metoptic canal and a type of canal that to our knowledge has never been reported. Warwick’s foramen was found in 0.74 % of orbits. The area of the optic strut is the frequent site of canals joining the orbit with the middle cranial fossa. Some of them can host the ophthalmic artery; others could be run by minor vessels which, however, could be the source of annoying bleedings in surgical procedures.