Microsurgical Anatomy of the Orbit: The Rule of Seven

Figure 8

Topographic classification of orbital lesions. The periorbit, the muscular cone, the optic nerve, and the superior orbital fissure are important structures in the topographical arrangement of the orbit. The presence of the periorbit allows classifying the orbital lesions in intradural—when deep to the periorbit—and extradural—when located between the periorbit and the bony orbit. The muscular cone divides the orbit into intraconal and extraconal spaces. While the intraconal lesions are always intradural, the extraconal lesion can be either intra- or extradural. The intraconal space also can be further subdivided in relation to the optic nerve into medial, central, and lateral orbital spaces.