inferior ophthalmic vein
The inferior ophthalmic vein begins in a venous net-work at the forepart of the floor and medial wall of the orbit; it receives some vorticose veins and other veins from the Rectus inferior, Obliquus inferior, lacrimal sac and eyelids, runs backward in the lower part of the orbit and divides into two branches. One of these passes through the inferior orbital fissure and joins the pterygoid venous plexus, while the other enters the cranium through the superior orbital fissure and ends in the cavernous sinus, either by a separate opening, or more frequently in common with the superior ophthalmic vein.