Lacrimal Dilator-Facilitated vs Standard Sub-Tenon's Block

Overview

Standard sub-Tenon's block involves incision (dissection) of conjunctiva and Tenon's capsule with the help of blunt scissors and forceps, insertion of a blunt sub-Tenon's cannula under the Tenon's capsule and injection of local anaesthetic agent. This block is frequently associated with minor complications such as chemosis and subconjunctival haemorrhage. Different variations of incisionless sub-Tenon's block including the use of lacrimal dilator have been described to reduce minor complications and facilitate insertion of blunt cannula. Lacrimal dilator creates a small aperture in the conjunctiva and Tenon's capsule thus avoids incision. After ethics approval, patients undergoing elective cataract surgery were enrolled to receive sub-Tenon's block performed without incision with a lacrimal dilator (Group LD) or with incision using Wescott scissors and blunt forceps (Group WS). All patients received 3 mL 2% lidocaine without any adjuvant. No sedation was administered. Demographic of the patients, duration of the procedure, analgesia (pain), akinesia, duration of the procedure intraoperative chemosis, subconjunctival haemorrhage on the first postoperative day. We aimed to compare lacrimal dilator-facilitated and standard sub-Tenon's block effectiveness and incidence of chemosis and subconjunctival haemorrhage.

The patients were randomly allocated to receive STB performed with a lacrimal dilator (Group LD) and with a Wescott scissors (Group WS). Randomization was ensured by sealed envelopes prepared according to a computer-generated table and the envelopes were opened by the operator just before the sub-Tenon's block. Study protocol Local anaesthetic eye drops were installed into the conjunctiva, followed by iodine 5% aqueous drops to the conjunctival sac for 3 minutes.19 An eye lid speculum was inserted. In group LD, the conjunctiva and Tenon's capsule were lifted together tightly with a blunt forceps like a tent in the inferonasal quadrant and a punctal dilatator was placed tangential to the globe creating a round and small hole at 5 mm posterior to limbus. The block was performed using smooth rounded tip, 19 G, 1 inch sub-Tenon's cannula . In Group WS, after lifting the conjunctiva and Tenon's capsule together with a blunt forceps, incision was performed with a blunt tip Westcott scissors in the inferonasal conjunctival at 5 mm posterior to limbus to expose sub-Tenon's space. The block was performed with the above sub-Tenon's cannula. All patients received lidocaine 2%, 3 mL without any adjuvant. No sedative was administered. All the blocks and surgeries were performed by the same investigator, but block evaluations were made by another investigator who was blinded to the technique used. All patients were discharged on the day of surgery. The parameters recorded included demographic of the patients, duration of the procedure, analgesia (pain), akinesia, duration of the procedure intraoperative chemosis, subconjunctival haemorrhage on the first postoperative day. Analgesia was evaluated using a numeric rating scale for pain (0-10; 0 - no pain, 10 - the worst imaginable pain) immediately after the operation. Akinesia (ocular movements) were checked according to 4-primary gazes 10 minutes after STB. Chemosis and conjunctival haemorrhage (1st postoperative day) were assessed according to the number of quadrant or quadrants affected (superior nasal, superior temporal, inferior nasal, inferior temporal) using a 5-point scale (0-4; 0 - no for chemosis and haemorrhage, 4 for chemosis or haemorrhage in all 4 quadrants).