The effect of sub-Tenon's anaesthesia on intraocular pressure

Purpose To assess the effect of sub-Tenon's anaesthesia on intraocular pressure (IOP) prior to cataract surgery. Methods Fifty consecutive patients undergoing phacoemulsification of cataract were recruited. Routine sub-Tenon's anaesthesia was administered with 5 ml unpreserved 2% lignocaine. IOPs were measured immediately prior to and at 1, 3, 5 and 10 min after injection. Efficacy was assessed subjectively by the operating surgeon. No ocular compression was used. Pre- and post-injection IOPs were compared using the Wilcoxon signed rank test, whereas all other results were compared with baseline using Student's two-tailed paired t-tests. Results All patients achieved good analgesia and akinesis. There was no significant difference between the LOP prior to and 1 min after injection. At all time intervals after 3 min there was a significant reduction in LOP compared with the pre-injection measurement. At 5 min, the mean LOP reduction was 2.72 mmHg and at 10 min LOP was lowered by 2.92 mmHg. Both reductions were statistically significant compared with baseline. Conclusions Sub-Tenon's anaesthesia does not cause any significant rise in LOP, thereby possibly making it the anaesthetic technique of choice when an increase in LOP is undesirable. There is no indication for the use of an ocular pressure-reducing device when sub-Tenon's anaesthesia is employed.