Flexible cannulas are safest for akinesia and anaesthesia in the latest comparison study on sub-Tenon cannulas.

A team led by Dr Waleed Riad, King Khaled Specialist Eye Hospital, Riyadh, Saudi Arabia, conducted a prospective, blind, randomized comparison between metal posterior, flexible posterior and flexible medium sub-Tenon cannulas forakinesia and anaesthesia.

The investigation included 159 patients who underwent cataract surgery under sub-Tenon block. All patients received a combination of bupivacaine and lidocaine with hyaluronidase.

Patients were divided into three groups. Group 1 received a metal posterior sub-Tenon cannula, group 2 had a flexible posterior sub-Tenon cannula and group 3 had a flexible medium sub-Tenon cannula. The outcome measures included pain during injection, akinesia, anesthesia, and complications.

Two minutes after injection the akinesia score, superior oblique muscle activity, lid movements and pain during injection was significantly lower in group 1. However, after four, six, eight and ten minutes there was no significant difference between cannulas.

Intraoperative pain was low for all groups but chemosis was significantly lower in group 2 and was found to be safer than the rigid cannulas.

The abstract can be found in the Journal of Cataract and Refractive Surgery .