Sub-Tenon's anesthesia

Sub-Tenon's anaesthesia for modern eye surgery-clinicians' perspective, 30 years after re-introduction

Sub-Tenon's block (STB) is a good technique of local anaesthesia for many types of eye surgery. It has a relatively good risk profile, in that sight- and life-threatening complications appear to be extremely rare. STB has gained popularity in the last three decades, with refinements including different types of blunt metal cannula, plastic cannulae and 'incisionless' approaches. Usage of STB varies significantly across the globe. This narrative review documents the historical evolution of STB techniques, anatomical and physiological considerations, its utility and suitability, complications, explores the current practice and possible future applications.

Localization of local anesthetic solution by magnetic resonance imaging

PURPOSE

The aim of this study was to examine the distribution of local anesthetic solution by magnetic resonance imaging (MRI) after combined peribulbar and retrobulbar, superomedial retrobulbar, and sub-Tenon's injection in relation to clinical akinesia.

DESIGN

Randomized clinical trial.

PARTICIPANTS

Fifteen patients scheduled for cataract surgery, 5 patients in each group.

METHODS

Five patients received combined peribulbar and retrobulbar anesthesia, 5 patients received superomedial retrobulbar injection, and 5 patients had sub-Tenon's injection, all with a combination of bupivacaine 0.75%, lidocaine 2%, and hyaluronidase. The MRI scans were performed before the injection and up to 35 minutes after the injection.

RESULTS AND CONCLUSIONS

Reliable anesthesia is achieved using a combined peribulbar and retrobulbar block and a relatively great volume of local anesthetic solution, which spreads throughout the orbit, as evidenced by MRI. After superomedial retrobulbar and sub-Tenon's injection, the local anesthetic solution accumulates behind the globe. Sub-Tenon's injection gives good analgesia and slight akinesia with a very small volume. Superomedial retrobulbar injection and combined peribulbar and retrobulbar block provide a similar degree of exophthalmos, which seems to be the result of the volume injected behind the globe.