Comparison of i.v. cannula and Stevens' cannula for sub-Tenon's block

Sub-Tenon's local anaesthesia (STLA) is growing in popularity for ophthalmic surgery, and is widely regarded as safer than the alternative sharp needle techniques. Although safe, STLA is not devoid of risk. Therefore, the effectiveness of a plastic i.v. cannula was compared with the traditional metal Stevens' cannula for delivering STLA.

In a randomized, controlled trial, the efficacy of STLA administered by either a Stevens' sub-Tenon's metal cannula or a standard 20 G Optiva i.v. plastic cannula was compared; 120 patients, undergoing cataract surgery, were randomly allocated to one of the two groups. After STLA, the primary outcome measure, kinesia of the globe, was recorded at 5 and 10 min.

There was no significant difference in the mean total ocular movement scores after STLA performed by either the 20 G i.v. cannula or standard 19 G sub-Tenon's cannula (P = 0.10). There was also no significant difference in any of the secondary outcome measures.

A 20 G Optiva i.v. cannula and the Stevens' sub-Tenon's cannula were equally effective at providing STLA.