Fig. 45-5. The chief contents of the orbit. A, superior orbital fissure and optic canal, anterior aspect. The optic canal and adjacent part of the fissure are surrounded by the common tendinous ring, from which the four recti arise. The lacrimal, frontal, and trochlear nerves enter the orbit above the ring. The superior and inferior ophthalmic veins leave the orbit usually above and below the ring, respectively. The optic canalcontains the optic nerve and the ophthalmic artery. The optic nerve is surrounded by its dural sheath (and by the subarachnoid space, as shown in figure 46-4). B, a superposable view showing the muscular cone anterior to the common tendinous ring. All the structures that pass through the ring lie at first within the muscular cone. The ophthalmic artery crosses (usually above) the optic nerve and is accompanied by the nasociliary nerve. The nerves to the extraocular muscles are shown in green, the sensory nerves in yellow, and the ciliary ganglion in mauve. The short ciliary nerves arise from the ganglion. A is modified from Wolff and from Whitnall; B is based partly on von Lanz and Wachsmuth. Click for high resolution image.