Microsurgical Anatomy of the Orbit: The Rule of Seven
Figure 9
(a) Intraorbital routes. The left orbit is seen from above as in a cranio-orbital approach. Medial, central, and lateral routes can be chosen pending on the location of the lesion to the optic nerve. (b) The medial route is performed between the superior oblique and superior muscular complex. This route gives access to the optic nerve from the globe to apex. The annulus can be opened for further access to the apex, with careful handling of the troclear nerve which courses from lateral to medial in this area. The medial space can also be reached by working endoscopically through the nasal cavity and medial orbital wall, beyond the medial rectus muscle. (c)-(d) The central route is taken by opening the periorbit and splitting the superior muscular complex. This is the shortest route to the central part of the optic nerve and to lesion situated along this area as a meningioma of the optic nerve sheath (d). The central route has two variants, pending on traction over the frontal nerve, which can be retracted medially, with the levator palpebrae muscle or laterally with the superior. On this last variant, access granted to the apical part of the optic nerve is broader, but it requires not only dissecting and displacing the frontal nerve but also opening the orbital septum. (e)-(f) The lateral intraorbital route gives access to the major space around the optic nerve. This space can be reached from above, by working between the superior muscular complex and lateral rectus muscle or laterally after a lateral orbitotomy is accomplished and is suitable for lesions located in this area, as orbital hemangiomas (f).
