Anatomy of the orbit and its related structures

A comprehensive knowledge of orbital and periorbital anatomy is necessary to understand disorders in these regions and to apply medical and surgical management appropriately and safely. The configuration of the bony orbit resembles a four-sided pyramid that becomes three-sided near the apex, with a volume of approximately 30 cm(3). The adult orbital rim measures, on average, 40 mm horizontally and 35 mm vertically, with the widest dimension of the orbit 1 cm behind the anterior orbital rim. The medial walls are roughly parallel and are 25 rum apart in adults. The length of the medial orbital wall from the anterior lacrimal crest is 45 to 50 mm, whereas the lateral wall from the rim to the superior orbital fissure measures 40 mm [1,2]. The lateral orbital walls are angled 90 degrees from each other. The lateral orbital rim is approximately at the level of the equator of the globe. The globe has an average volume of 6.5 cm(3) and has a shape formed by two spheres, the cornea and the sclera, with radius of curvatures equal to 8 and 12 mm, respectively [2]. Globes in the average adult and newborn infant measure 24 mm and 16.4 mm, respectively, in the anteroposterior dimension.