Sub-Tenon's anesthesia and orbicularis oculi function

BACKGROUND AND OBJECTIVE: To assess the necessary volume of local anesthetic with added hyaluronidase that must be infiltrated to the sub-Tenon's space to achieve complete eyelid akinesia. PATIENTS AND METHODS: Eighty-five consecutive patients were randomly assigned to two groups, receiving either 5 ml or 7 ml of local anesthetic to the sub-Tenon's space. Each patient was assessed clinically at 5 and 10 minutes for orbicularis oculi function. The anesthetic solution consisted of 5 ml of 2% lidocaine, 5 ml of 0.75% bupivacaine hydrochloride, and 1500 IU of hyaluronidase. A top-up of anesthetic infiltration was given in doses of 2 ml if excessive orbicularis muscle function persisted at 10 ml. Routine phacoemulsification surgery was performed, and, if necessary, a top-up of anesthetic was given on the table. RESULTS: Complete eyelid akinesia was achieved in 7.5% (3 of 40) of the patients in the 5-ml group and in 93.3% (42 of 45) of the patients in the 7-ml group (P < .005). There was no effect for 57.5% (23 of 40) of the patients in the 5-ml group and for 2.2% (1 of 45) of the patients in the 7-ml group. A top-up of anesthetic was given in the anesthetic room to 40 patients, 37 of whom were in the 5-ml group, and a Van Lint block of the facial nerves was necessary for 1 patient from the 5-ml group. An on-the-table top-up of anesthesia was necessary for 3 patients (2 from the 5-ml group, 1 from the 7-ml group). CONCLUSIONS: The addition of hyaluronidase promotes diffusion of sub-Tenon's anesthetic, resulting in effective akinesia of the orbicularis oculi. The infiltration of 7 ml of the anesthetic solution significantly improves the rate of eyelid akinesia.