Fig. 2. (A ) Semischematic view of a horizontal section of the orbit. 1 = Common insertion of bulbar conjunctiva and Tenon capsule on the eyeball, near the sclerocorneal limbus; 2 = anterior facial sheath of the eyeball (the Tenon capsule); 3 = sclera; 4 = medial rectus muscle; 5 = episcleral space (sub-Tenon); 6 = posterior facial sheath of the eyeball; 7 = lateral rectus muscle. Note the continuity between the Tenon capsule and the sheaths of the rectus muscles. (B ) Same view as A , with figurated spread of a local anesthetic injected into the peribulbar space, with subsequent spread into the muscular cone. Because the space for spreading is the adipose tissue of the orbit, including small septas network, this spread may be incomplete or heterogeneous, thus accounting for imperfect blocks. (C ) Same view as A , with figurated spread of a local anesthetic injected into the episcleral (sub-Tenon) space. Note the spreading into the whole episcleral space and into the sheaths of the rectus muscles, thus accounting for good akinesia. Because the episcleral space is adherence-free and septum-free, this spread is more constant, thus accounting for more constant akinesia. Additionally, because the anterior Tenon is not tightly sealed, part of the local anesthetic flows to the lids, accounting for akinesia of the orbicularis muscle.