Lacrimal Dilator-Facilitated vs Standard Sub-Tenon's Block
Condition: to Compare Lacrimal Dilator-facilitated Incisionless and Standard STB With Wescott Scissors
Study type: Interventional

Summary: 
      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.
    

Detailed description: 
      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).
    

Intervention name(s): sub-Tenon's block with a lacrimal dilator group or a Wescott scissors
Intervention type(s): Device
Intervention description(s): 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 (Castroviejo Lacrimal Dilatator, Katena Products, Inc, Denville, NJ, USA) was placed tangential to the globe creating a round and small hole at 5 mm posterior to limbus (Fig.1). The block was performed using smooth rounded tip, 19 G, 1 inch sub-Tenon's cannula (Visitec, Beaver-Visitec International Ltd, Warwickshire, UK).
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.
Allocation: Randomized
Intervention model: Parallel Assignment
Intervention model description: a randomized, prospective, non-inferiority comparative study
Masking: Triple (Participant, Investigator, Outcomes Assessor)
Primary purpose: Treatment
Keywords: sub-Tenon's block, lacrimal dilator, Wescott scissors, chemosis, subconjunctival haemorrhage