Comparison of retrobulbar and sub-Tenon's capsule injection of local anesthetic in vitreoretinal surgery.

OBJECTIVE To compare the efficacy and efficiency of retrobulbar versus sub-Tenon's capsule injection of local anesthetic in vitreoretinal surgery. DESIGN Prospective, randomized, double-masked clinical trial. PARTICIPANTS AND INTERVENTION Sixty-four eyes from 61 patients undergoing vitreoretinal surgery were randomized to receive either retrobulbar or sub-Tenon's capsule injection of 5 ml of a 50:50 mixture of 4% lidocaine and 0.75% bupivacaine. MAIN OUTCOME MEASURES The primary outcome measured was intraoperative eye pain, which was rated by patients in both groups using an 11-point (0-10) numerical visual analogue scale immediately after surgery and again the next morning. The surgeons indicated whether they perceived patient discomfort during 4 different stages of the operation: opening of the conjunctiva, vitrectomy (if performed), placement of scleral buckle (if performed), and closing of the conjunctiva. The preincision time, need for supplemental local anesthesia, and use of IV sedation for additional pain control were compared between the two groups. RESULTS Thirty-four eyes were randomized to retrobulbar injections, and 30 eyes were randomized to sub-Tenon's capsule injections. There was no significant difference in patient-reported intraoperative pain scores between the retrobulbar and sub-Tenon's capsule groups when assessed immediately after surgery (median, 2.0 vs. 2.0; P = 0.52) or the next day (median, 2.0 vs. 1.0; P = 0.26). The surgeons reported no difference between the two groups in terms of the percentages of patients with pain during opening of the conjunctiva (20.6% vs. 3.3%; P = 0.058), vitrectomy (31% vs. 32%; P = 1.00), placement of scleral buckle (33.3% vs. 40%; P = 1.00), and closing of the conjunctiva (26.5% vs. 26.7%; P = 1.00). There was a suggestion that preincision time was longer in the sub-Tenon's capsule group. Approximately equal percentages of patients in each group required supplemental local anesthesia (38% vs. 37%; P = 0.90) or IV medication (85% vs. 70%; P = 0.14) for pain control. CONCLUSIONS Sub-Tenon's capsule injection of local anesthetic seems as effective as retrobulbar injection at controlling intraoperative pain in vitreoretinal surgery.