Vascular Diseases of the Optic Nerve: Internal Medicine Aspects

Blood vessels supplying ocular structures originate from the internal carotid artery, so the blood supply of the eyes and the brain are closely connected. The various branches of the ophthalmic artery (central retinal artery, short and long posterior ciliary arteries, lacrimal artery, anterior ciliary artery) originating from the internal carotid artery and the corresponding veins are responsible for supplying the region indicated by their name. In rare cases, when the ophthalmic artery is absent, the medial meningeal artery performs the same task. The uvea is supplied by the ciliary artery, and the retina gets its blood supply from the branches of the central retinal artery. The posterior ciliary arteries (that supply the optic disc) and the central retinal artery (that supplies the medial two-thirds of the retina) are the first arteries to branch off the ophthalmic artery that enters through the optic foramen. The central retinal artery divides into superior temporal, inferior temporal and nasal branches. The next vessels to branch off are the long posterior ciliary arteries that supply the peripheral parts of the choroidea, the ciliary body and the iris. The last branch is that of the anterior ciliary arteries. Venous drainage from the retina is carried out by the central retinal vein and its smaller branches that have the same name and course as the corresponding arteries. The vorticose veins drain the choroidea towards the inferior and superior ophthalmic vein and the cavernous sinus. The capillary network between the retinal arteries and veins serves to ensure overly efficient oxygen and nutrient exchange. It is only the macula lutea (responsible for acute vision) and the fovea centralis that have no capillaries. Another special feature of these vessels is that retinal blood vessels have the same structure as cervical ones, and it is also true for uveal and extracranial vessels. These veins and arteries are located very close to each other, sometimes in the same adventitia sheath.