Sub-Tenon’s block has become the most common technique of orbital regional anesthesia in many centers. It provides effective anesthesia to the orbit with a lower incidence of sight-threatening complications than sharp needle techniques. This article will discuss the relevant anatomy, finer points of sub-Tenon’s block technique, and the evidence supporting its safety.

The experience at Auckland Hospital provides further support for the avoidance of passing sharp needles into the orbit.

The role of hyaluronidase on the onset time and quality of single quadrant sub-Tenon's block was studied in a prospective, randomized, double-blind controlled manner. One hundred and twenty consecutive patients undergoing cataract surgery under local anaesthesia received a sub-Tenon's block with either of two local anaesthetic solutions. One consisted of 2% plain lignocaine 3 ml with 0.5% plain bupivacaine 2 ml. The other consisted of 2% lignocaine 1 ml containing 150 IU per ml of hyaluronidase with 2% plain lignocaine 2 ml and 0.5% plain bupivacaine 2 ml. The development of akinesia and the resulting block quality were assessed. Akinesia scores were lower at all time intervals and were significantly lower (P<0.05) up to 9 minutes after block in the hyaluronidase group. However, block quality as assessed by the surgeon was not significantly different between the groups. The addition of 150 IU hyaluronidase significantly speeds up the onset of surgical anaesthesia produced by a sub-Tenon's block.

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There is a lack of data to support either continuation or interruption of non–vitamin K oral anticoagulants for cataract and vitreoretinal surgery. A prospective audit was undertaken of 291 patients undergoing cataract surgery or vitreoretinal surgery, predominantly under sub-Tenon’s block, while continuing these agents. The median time from last non–vitamin K oral anticoagulant dose to the insertion of sub-Tenon’s block was five hours. No patient required emergency reversal of anticoagulation. There were no sight-threatening complications in the immediate perioperative period, although two vitreoretinal patients (3.8%) had a moderate haemorrhagic complication on day five, and two cataract patients (0.8%) had a minor haemorrhagic complication on days one and 14 postoperatively. Despite continuing their non–vitamin K oral anticoagulants, three (1%) cataract patients had a moderate thromboembolic complication within the 30-day postoperative period. The risk of haemorrhagic complications associated with continuation of anticoagulation with non–vitamin K oral anticoagulants for cataract and vitreoretinal surgery is low, and this audit supports the continuation of non–vitamin K oral anticoagulants for our patients having cataract and vitreoretinal surgery.