[Gross anatomical study of veins in the orbit]

The aim of this study is to clarify the major route of venous return in the orbit. Minute dissections were performed in 10 adult cadavers (5 males and 5 females) after being fixed in a 10% formalin solution. The superior ophthalmic vein (SOV) and its ascending anastomotic branch were consistently well-developed (the average maximum diameter: 6.2mm and 3.2mm, respectively) and these two veins formed the main venous channel from the orbital contents. The ascending anastomotic branch ran between the optic nerve and the medial rectus just behind the eyeball and joined the SOV. A large number of veins, including the inferior ophthalmic vein, which originated from the inferior contents of the orbit, drained into the ascending anastomotic branch. Arteries and/or nerves did not accompany their respective veins in the orbit, except for the lacrimal and ethmoidal veins. The posterior end of the SOV was severely narrowed lateral to the aponeurosis of the lateral rectus, while being conspicuously dilated just behind the eyeball. The above findings suggested that the dilated portion of SOV may act as a reservoir of the venous return of the orbit.