Functional importance of central retinal artery anastomoses in the anterior part of the optic nerve.

A three-dimensional study showed the existence of three vascular networks in the optic nerve: a peripheral, a periaxial and an axial one. The axial network, which was seen in 30% of the specimens, was formed by ramifying collateral branches from the pia mater of the optic nerve, but in the anterior part of the optic nerve there was an axial system which entirely depended on branches of the central retinal artery. This artery had important anastomoses with branches originating from the pia mater of the optic nerve and other collateral branches originating from the ophthalmic artery and its branches (the ciliary system).