SUB-TENONS ANESTHESIA AND ORBICULARIS OCULI FUNCTION

BACKGROUND AND OBJECTIVE: To assess the necessary volume of local anes thetic with added hyaluronidase that must be infiltrated to the sub-Te non's space to achieve complete eyelid akinesia. PATIENTS AND METHODS: Eighty-five consecutive patients were randomly assigned to two groups , receiving either 5 mi or 7 mi of local anesthetic to the sub-Tenon's space. Each patient was assessed clinically at 5 and 10 minutes for o rbicularis oculi function. The anesthetic solution consisted of 5 mi o f 2% lidocaine, 5 mi of 0.75% bupivacaine hydrochloride, and 1500 IU o f hyaluronidase. A top-up of, anesthetic infiltration was given in dos es of 2 mi if excessive orbicularis muscle function persisted at 10 mi . Routine phacoemulsification surgery was performed, and, if necessary , a top-up of anesthetic was given on the table. RESULTS: Complete eye lid akinesia was achieved in 7.5% (3 of 40) of the patients in the 5-m l 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-tab le 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 hyaluronid ase promotes diffusion of sub-Tenon's anesthetic, resulting in effecti ve akinesia of the orbicularis oculi. The infiltration of 7 mi of the anesthetic solution significantly improves the rate of eyelid akinesia .