Comparison of metal and flexible sub-Tenon cannulas

To compare metal posterior, flexible posterior, and flexible medium sub-Tenon cannulas for akinesia and anesthesia.

King Khaled Specialist Eye Hospital, Riyadh, Saudi Arabia.

Prospective blind randomized comparison.

Patients having cataract surgery under sub-Tenon block received a mixture of bupivacaine and lidocaine with hyaluronidase. The patients were divided into 3 groups based on whether a metal posterior sub-Tenon cannula, flexible posterior sub-Tenon cannula, or flexible medium sub-Tenon cannula was used. Pain during injection, akinesia, anesthesia, and complications were recorded.

The study enrolled 159 patients. The akinesia score, superior oblique muscle activity, lid movements, and pain during injection were significantly lower in the metal posterior cannula group 2 minutes after injection (P=.002, P=.008, P=.097, and P=.001, respectively); there was no significant difference at 4 minutes, 6 minutes, 8 minutes, and 10 minutes. The incidence of intraoperative pain was low in all groups (P=.607). Chemosis was significantly less in the flexible posterior cannula group (P=.003); however, there was no significant difference in the site of chemosis (P=.460). There was no significant difference in the incidence, site, or severity of subconjunctival hemorrhage (P=.087, P=.072, and P=.331, respectively). No serious complications occurred.

Rigid posterior, flexible posterior, and flexible medium cannulas produced effective and equivalent anesthesia. The flexible cannulas may be safer than the rigid cannulas.

No author has a financial or proprietary interest in any material or method mentioned.