Fig. 12. Annulus of Zinn. III-S, superior division of oculomotor nerve; III-I, inferior division of oculomotor nerve; IV, trochlear nerve; VI, abducens nerve; L, lacrimal nerve; F, frontal nerve; N, nasociliary nerve; SRM, superior rectus muscle; LEV, levator palpebris superioris muscle; SOM, superior oblique muscle; MRM, medial rectus muscle; IRM, inferior rectus muscle; LRM, lateral rectus muscle. (Modified from Zide BM, Jelks GW: Surgical Anatomy of the Orbit, p 8. New York, Raven Press, 1985)