A comparison of three sub-Tenon's cannulae

Abstract

Purpose. To compare the quality of anaesthesia and complication rates between three sub-Tenon cannula of increasing length (anterior Greenbaum, mid Kumar-Dodds, and posterior Steven's sub-Tenon's cannulae). Methods. A total of 150 patients undergoing cataract extraction were randomised to receive a sub-Tenon injection of 5ml of 2% lidocaine with hyaluronidase with one of the three cannulae. The development of akinesia was assessed every 2min over a 6-min-period. Complications were also recorded. Results. There was no difference in the onset of akinesia, with 46, 50, and 46 patients achieving adequate akinesia within 6min for the anterior, mid, and posterior groups respectively (P>0.05). There was an increase in retained lid opening with anterior compared to mid and posterior cannulae P = 0.0001). There was significantly less retained lid closure with the posterior compared to the mid or anterior cannulae (P<00001). The mean (range, SD) scores for pain during injection were 0.4 (0-5, 0.83), 1.2 (0-9, 1.96), and 1.1 (0-6, 1.19) for the anterior, mid, and posterior groups, respectively. These were not significantly different between the anterior and mid groups, or the mid and posterior groups (P=>0.05), but there was significantly more pain on injection with the posterior compared to the anterior groups (P<0.01). All patients scored intraoperative pain as zero. There was significantly more chemosis in the anterior group (76%) compared to the mid (20%) and posterior (32%) groups (P<0.0001). There were significantly (P= 0.0004) more conjunctival haemorrhages in the anterior group (56%) than the mid (20%) or posterior (20%) groups. Conclusions. We have shown that all three cannulae provide high-quality anaesthesia with minor differences in retained muscle activity, chemosis, and haemorrhage rates. © 2004 Nature Publishing Group All rights reserved.