Using two-quadrant sub-Tenon's anaesthesia is more effective at reducing intraoperative and postoperative pain than a single-quadrant technique, states a study in the 

, Department of Anaesthesia, Guy's and St Thomas' Hospital NHS Foundation Trust, London, UK, studied 54 patients undergoing vitrectomy. All patients were equally randomized into two groups.

Group A, the control, were administered a standard 5 ml single inferonasal sub-Tenon injection of 2% lidocaine and 0.5% bupivacaine in a 50:50 mixture. Group B, the study group, received a 5 ml inferonasal and 5 ml superotemporal injection.

Primary outcome measures included amount of intraoperative top-ups needed and the secondary outcome measures included intraoperative and postoperative pain scores, IOP, block onset time, ocular akinesia, eyelid akinesia and chemosis.

In the group V there were no patients requiring an anaesthetic top-up, but in the control group a top-up was needed in 24 patients. In group B block onset was shorter, eyelid akinesia was improved and pain scores were reduced intraoperatively and 0–2 hours (h), 4–6 h, 10–14 h and 20–24 h postoperatively.

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Using two-quadrant sub-Tenon's anaesthesia is more effective at reducing intraoperative and postoperative pain than a single-quadrant technique.