MEDIAL CANTHUS SINGLE-INJECTION EPISCLERAL (SUB-TENON ANESTHESIA) - COMPUTED-TOMOGRAPHY IMAGING

Single-injection medial canthus periocular anesthesia is a promising r egional anesthesia technique for ophthalmic surgery. The purpose of th is computed tomography (CT) study was to confirm that this technique i s an episcleral injection and to explain why it provides a good akines ia of the globe. Four fresh nonpreserved cadavers (eight eyes) were in jected with fractioned various volumes of a contrast media using a pre viously described technique. For each injection and each eye, CT scans were performed in three planes of the space, and the site and spread of the injection was observed. We confirm that single-injection medial canthus periocular anesthesia is, in fact, an episcleral anesthesia, which explains the good sensory block of the globe. When larger volume s are injected, the contrast media spreads to the lids and extraocular muscle sheaths. We believe that this may explain why this technique p rovides good sensory and motor block of the globe and eyelids. This te chnique is a promising alternative to both retro- and peribulbar anest hesia. Implications: We describe medial canthus single-injection perio cular anesthesia by a computed tomography injection study in eight hum an cadaver eyes. It was confirmed to be an episcleral injection. Akine sia of the eyeball is provided by spreading of the local anesthetic so lution from the episcleral space to the rectus muscle sheaths.