Comparison of Anesthetic Efficacy and Intraocular Pressure by Volume of Sub-Tenon's Anesthetic in Vitreoretinal Surgery

ABSTRACT

PURPOSE: To compare the effects of different volumes of sub-Tenon's anesthetic on intraocular pressure (IOP) and to evaluate the treatment efficacy of vitreoretinal surgery. METHODS: A prospective, clinical trial was conducted on patients undergoing sub-Tenon's anesthesea for vitreoretinal surgery. Patients were randomized to receive either 3 mL, 5 mL or 7 mL of anesthetic solution. IOPs were measured immediately prior to, immediately after, and at 2, 5 and 10 min after the injection. Pain scores were assigned using a numerical visual analogue scale immediately following surgery and again on postoperative day one. RESULTS: A total of 108 patients (119 eyes) were studied, including 35 eyes in the 3 mL group, 48 eyes in the 5 mL group, and 36 eyes in the 7 mL group. There was significant elevation in mean IOP following injection in all groups and a trend toward a larger increase in the group receiving the larger volume (p<0.01). Mean IOPs were elevated immediately after the injections and reduced at all subsequent time intervals. But reduction to the pre-injection level was only achieved in the 3 mL group. There was no significant difference in patient-reported pain scores among the groups when assessed immediately after surgery or on postoperative day one. The incidence of chemosis and high IOP elevation (40 mmHg < or =) was more frequent in the 7 mL group than the other groups (p<0.05). CONCLUSIONS: Sub-Tenon's anesthesia is effective in vitreoretinal surgery. It would appear that a 3-5 mL volume of anesthetic is safe even when complications are considered.