The intraorbital course of ophthalmic artery and its relationship with the optic nerve

Most intraorbital structures are supplied by branches of the ophthalmic artery (OA) which is the first branch of the internal carotid artery after it exits from the cavernous sinus. OA, proceeds in optic canal embedded in dura mater of the optic nerve [1]. Within OA’s branches, there are pial vessels and central retinal artery, a main intraneural branch. In addition to these, there is a strong anastomosis networks between branches of external carotid artery and orbital arteries. The OA can be sacrificed during aneurysm clipping without loss of vision in many cases, most likely because of adequate collateral filling from the external carotid artery [2]. Therefore, while the obstruction of central retinal artery leads to a sudden blindness (amaurosus fugax), OA obstructions may be asymptomatic. Optic nerve is 50 mm in length from its originating point at sclera to optic chiasm and it consists of four parts: 1) intraocular, 2) intracanalicular, 3) intraorbital and 4) intracranial. The intracranial part of the optic nerve is supplied by internal carotid artery, anterior cerebral artery, anterior communicating artery and OA. Transition of OA branches from dural sheaths enveloping the optic nerve and their entrance to the nerves are clinically important [3,4]. At the orbital surgery, awareness of the relationship ophthalmic artery with optic nerve may be important for reduce surgical damage. The course of OA is important because it indicates the relationship between the optic nerve and the surrounding structures from the topographic and morphometric viewpoints and reduces such complications mentioned above. For this reason, we evaluated the origin, branches and the relationship of the OA with the optic nerve. We made the morphometric analysis of these structures.