Prospective study of sub-Tenon's versus retrobulbar anesthesia for inpatient and day-surgery trabeculectomy

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.

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.

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.

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.