Optic nerve and peripapillary choroidal microvasculature of the rat eye

PURPOSE. To investigate the three-dimensional microvascular anatomy of the optic nerve and peripapillary choroid in the rat eye. METHODS. Gross vascular anatomy of the posterior eye segment of Wistar rats was studied in serial microsections with a light microscope. The optic ner ve and peripapillary choroidal vessels were sequentially microdissected, us ing methylmethacrylate corrosion microvascular castings, and were examined with a scanning electron microscope to determine the three-dimensional rela tionships of the vessels. RESULTS. The posterior ciliary artery traveled along the inferior side of t he optic nerve sheath, directly entered the optic nerve head, and divided i nto three branches: the central retinal artery and medial and lateral long posterior ciliary arteries, which provided several short branches to the ch oroid. The optic nerve head vasculature was consistently nourished by a rec urrent arteriole from the central retinal artery and an arteriole from the choroidal artery at the peripapillary choroid. The central retinal vein flo wed into a venous anastomosis along the optic disc border of the peripapill ary choroid. Capillaries within the optic nerve drained into the central re tinal vein, the marginal venous anastomosis of the peripapillary choroid, a nd the pial veins, all of which. flowed into the posterior ciliary veins al ong the optic nerve sheath. CONCLUSIONS. The findings illustrate vascular anatomic differences in optic nerve and peripapillary choroidal microcirculation between rat and human. In rats, the peripapillary choroid plays a significant role in both blood s upply and venous drainage of the optic nerve head. The central retinal arte ry also contributes to the optic nerve head circulation.