[Electron microscopy of the angioarchitecture of the human iris and ciliary body]

With the corrosion cast technique and electron microscopy, the major arterial circle of the iris, formed by the terminal branches of the medial and lateral long posterior ciliary arteries and of the anterior ciliary arteries, is shown not an anastomosed vascular ring but divided small branches of the arteries to supply the iris and ciliary body. The iris vessels demonstrate a radiate distribution of about 180-200 branches. The calibres of the iris arteries are homogeneous and measure about 50-120 microns. The branching portion of a precapillary arteriole begins with a constriction. The vessels of the ciliary processes account for more than half the volume of the ciliary body and have a rich capillary network of at least two layers. The draining veins are located on the surface and at the base of the ciliary body. There are 7-10 draining veins between two ciliary processes.