Dear Editor,

Sub-Tenon block is a safe, efficient and effective technique for delivering local anaesthesia for phacoemulsification cataract surgery.[1] Several studies have compared sub-Tenon's block with topical anaesthesia for intra-operative pain complications and the technique is found to be favourable.[2] We are not aware of any published study that has assessed post-operative pain (beyond 30 minutes post-operatively) for routine phacoemulsification using sub-Tenon's block.

We devised a questionnaire-based survey and asked 56 consecutive patients to comment on their experience of pain after routine and uneventful cataract surgery. Surgery was performed by one surgeon (TCD) and the sub-Tenon's was performed by one anaesthetist (CMK) in all cases. All patients received sub-Tenon's block using a 2.54cm long metal posterior sub-Tenon's cannula and 4 cc of 2% lidocaine was used. The questionnaire was designed to explore parameters of post-operative pain including severity, character, duration and associated symptoms. Severity was assessed using a visual analogue score from 0 (no pain) to 10 (severe pain). The patients were interviewed on the second post-operative day by telephone. The patients were also asked about any previous eye surgery and whether they were taking painkillers concomitantly for any other conditions.

Our results revealed that 51 (91%) patients had suffered no pain after surgery. However, 31 (61%) were on regular analgesics for other medical conditions whereas 20 (39%) were not taking any painkillers at all. Forty one patients had undergone previous cataract surgery. Of the five patients (9%) who suffered post-operative pain; 2 described immediate onset, with 1 patient each describing onset at 30 minutes, 2 hours and 24 hours after surgery respectively. Of these, 1 patient had spontaneous relief, whereas the other 4 required oral analgesia.

There was no notable correlation between those on regular analgesia and post-operative pain, however, the design and retrospective nature of the study precludes any conclusions from being drawn in this regard. A prospective, randomised controlled trial addressing these parameters in the future would be ideal.

We conclude that our survey supports other studies that the sub- Tenon's block is not only safe, effective and efficient but also provides good post-operative pain relief after routine phacoemulsification cataract surgery.

References

1. Ophthalmic regional anaesthesia. Kumar C, Dowd T. Curr Opin Anaesthesiol 2008;21(5):632-37.

2. Sub-Tenon's anaesthesia versus topical anaesthesia for cataract surgery. Davison M, Padroni S, Bunce C, Ruschen H. Cochrane Database Syst Rev 2007;3:CD006291.

Conflict of Interest:

None declared