Purpose: Several retrospective studies have demonstrated the safety and efficacy of sub-Tenon's anesthesia in ocular surgery. This is the first prospective randomized study comparing sub-Tenon's versus retrobulbar anesthesia for glaucoma surgery.
Methods: Thirty-nine patients undergoing both inpatient and day surgery trabeculectomy were randomized to receive retrobulbar or sub-Tenon's anesthesia. Retrobulbar anesthesia consisted of a 1.5-ml injection of a 1:1 mixture of 2% lidocaine without epinephrine and 0.5% plain bupivacaine with hyaluronidase. Sub-Tenon's anesthesia consisted of 2% lidocaine without epinephrine injected over the superior, medial and lateral recti muscles. Both groups received a van Lint lid block and a standardized sedative. Outcome parameters evaluated included patient demographics, operative complications, intraoperative and postoperative patient comfort, and volume of anesthetic.
Results: Seventeen patients were randomized to the retrobulbar group and 22 to the sub-Tenon's group. Patient discomfort was statistically similar between the groups. There was no statistical difference between groups with respect to quantity of sedative received, surgical exposure, eye movements, or operative complications. A retrobulbar hemorrhage, however, developed at the time of retrobulbar anesthesia in one patient, requiring cancellation of surgery. A larger volume of local anesthetic was required in the retrobulbar group versus the sub-Tenon's group (1.8 versus 1.1 ml; P < 0.01). Patients receiving retrobulbar injections were more likely to require additional anesthesia (P < 0.01) and postoperative analgesics (P < 0.05) compared with patients undergoing sub-Tenon's injection. There was no significant difference between the groups with respect to age, sex, or operated eye.
Conclusions: Sub-Tenon's anesthesia is safe and effective for patients undergoing either inpatient or day-surgery trabeculectomies, and it requires less local anesthetic than retrobulbar anesthesia.