Brief post on some of the facts on blood supply from optic nerve to head. Optic nerve is sullied by post ciliary artery branch of ophthalmic artery and ophthalmic artery is first branch of internal carotid artery distal to cavernous sinus according to s s harey a noted anatomist p c a after supplying the disc has got segmental distribution in choroid and choroidal arteries are end arteries so any condition which impairs with blood supply of p c a will not only produce changes in disc but also in peripapillary choroid cauterised by cavernous degeneration of optic nerve.