ABSTRACT
BACKGROUND: Total volume using a standard single inferonasal injection for sub-Tenon's anaesthesia is limited by an increase in intraocular pressure (IOP) and commonly requires the operating surgeon to top-up the block intraoperatively. This study compares the efficacy and safety of a two-quadrant technique that allows the use of a higher volume of local anaesthetic. METHODS: 54 patients undergoing vitrectomy were randomised into two groups. The control group (n=27) received a standard 5 ml single inferonasal sub-Tenon injection of a 50:50 mixture of 2% lidocaine and 0.5% bupivacaine with 150 IU hyaluronidase. The study group (n=27) received a 5 ml inferonasal and 5 ml superotemporal injection of the same mixture (10 ml total). The primary outcome measure was the number of intraoperative top-ups required. Secondary outcome measures were intraoperative and postoperative pain scores, IOP, block onset time, ocular akinesia, eyelid akinesia and chemosis. RESULTS: 24 patients required a top-up in the control group. No patients required a top-up in the study group (p<0.001). IOP measurements were similar in both groups. Block onset was shorter, eyelid akinesia was improved and pain scores were also reduced in the study group intraoperatively and at 0-2 h, 4-6 h, 10-14 h and 20-24 h postoperatively. CONCLUSIONS: Two-quadrant sub-Tenon's anaesthesia using 10 ml of a 50:50 mixture of 2% lidocaine and 0.5% bupivacaine with 150 IU hyaluronidase seems to be more effective than a single-quadrant technique at reducing intraoperative and postoperative pain during vitrectomy.
