Evaluation of the Greenbaum sub-Tenon's block

A prospective, randomized blind study was conducted in 40 patientsundergoing phacoemulsification and posterior chamber intraocularlens implantation. They received anaesthetic infiltration of2% lidocaine with 1:200 000 epinephrine and hyaluronidase150 U ml^–1 in a volume of 2, 3, 4 or 5 mlinto the sub-Tenon’s fascial space through a Greenbaumcannula after a conjunctival incision. Reduction of ocular movements,anaesthesia, pain on injection and any incidental complicationswere recorded. Akinesia and anaesthesia occurred within 5 minwith 4 and 5 ml of local anaesthetic, and no supplementaryinjections were required. There were marked reductions in thefrequency of forced eyelid movements with these volumes. Chemosisand conjunctival haemorrhage were noted in the majority of patientsbut caused no intraoperative problems. Approximately 10–15%of patients reported slight discomfort at the time of injection.Four to 5 ml of 2% lidocaine with 1:200 000 epinephrineand 150 U ml^–1 of hyaluronidase is the optimumvolume to achieve adequate akinesia, anaesthesia and reductionof lid movements during the Greenbaum sub-Tenon’s block. Br J Anaesth 2001; 87: 631–3