The vorticose veins, referred to clinically as the vortex veins, drain the ocular choroid. The number of vortex veins is known to vary from 4 to 8 with about 65% of the normal population having 4 or 5. In most cases, there is at least one vortex vein in each quadrant. Typically, the entrances to the vortex veins in the outer layer of the choroid (lamina vasculosa) can be observed funduscopically and provide an important clinical landmarks identifying the ocular equator. However, the veins run posteriorly in the sclera exiting the eye well posterior to the equator.
Some vortex veins drain into the superior orbital veins and thence to the cavernous sinus. Some vortex veins drain into the inferior orbital vein which drains into the pterygoid plexus. There is usually collateral circulation between the superior and inferior orbital veins.