Occasionally (18% to 32% of eyes), there is a cilioretinal artery from the ciliary circulation, which irrigates the macula. The vessel that crosses the horizontal raphe is called a congenital retinal macrovessel. This anatomical distribution is maintained throughout the retina, as normal retinal vessels rarely cross the horizontal raphe. Then, the upper and lower branches divide into their respective temporal and nasal branches. Immediately before leaving the optic nerve, the CRA divides into superior and inferior branches, which measure an approximate diameter of 80 μm at the level of the optic disc edge (contrasting with the average diameter of around 125 μm of the veins at this level). The CRA is considered a “terminal branch” since it does not present significant anastomoses with other arteries in its course. Retinal blood vessels from the CRA supply the inner two-thirds of the retinal thickness. The retina is supplied by two distinct vascular systems from important branches of the ophthalmic artery: The ophthalmic artery, the first intracranial subdivision of the internal carotid artery, gives rise to a series of arteries, responsible for nourishing the various ocular structures. 1.4 Study of vascularization of the posterior pole by OCT-A.1.3 Anatomy of the optic nerve vascularization.1.2 Anatomy of the choroidal vascularization.1 Vascular supply of the posterior pole.