One Quadrant Sub-Tenon's Capsule Anesthesia in Anterior Segment Surgery

Abstract

Reports of complications associated with local anesthesia in ophthalmic surgery have increased conspicuously in recent years. Sub-Tenon's capsule anesthesia for anterior segment surgery avoids the risks of retrobulbar and peribulbar injections. This study compared sub-Tenon's and retrobulbar anesthesia. Patients undergoing various anterior segment surgery were randomly assigned to sub-Tenon's or retrobulbar anesthesia; 300 were operated with 1-quadrant sub-Tenon's anesthesia (1-QST) and the results were compared with 270 patients operated with retrobulbar anesthesia.

Retrobulbar anesthesia consisted of a 2.5 ml injection of a 1: 1 mixture of 2% lidocaine without epinephrine and 0.5% bupivacaine. Sub-Tenon's anesthesia involved direct transconjunctival infiltration of the same local anesthetic directly into the sub-Tenon's space, in the inferior-nasal quadrant, using a blunt 23-gauge cannula. Patients undergoing various anterior segment surgery procedures were randomly assigned to 1-QST or retrobulbar anesthesia; 300 patients were operated with 1-QST and the results were compared with 270 patients operated with retrobulbar anesthesia.

Preinjection mean (±SD) IOP were 12.9±3.7 mmHg in the retrobulbar and 13.4±3.2 mmHg in the 1-QST patients. Preoperative intraocular pressures were 8.7±3.0 mmHg in the retrobulbar and 9.2±3.2 mmHg in 1-QST patients. Pre- and postinjection IOP for retrobulbar and 1-QST patients were similar.

Pain scores for delivery of the anesthetic, using a numerical rating scale, produced a median score of 1 for 1-QST and 2 for the retrobulbar technique. For the subsequent operative procedure, the median score was 1 for 1-QST and 2 for the retrobulbar patients. Complete akinesia was achieved in 41% with 1-QST and in 69% of retrobulbar patients. 1-QST patients with incomplete akinesia most often had lateral muscle function which did not interfere with the operation.

We found the use of a blunt cannula to deliver anesthetic into the sub-Tenon's space as a simple, safe and effective alternative approach to traditional retrobulbar anesthesia in anterior segment surgery.