Which anaesthetic technique is best?

Despite the increasing trend toward topical anaesthesia, injectable anaesthesia such as sub-tenon, peribulbar and less commonly retrobulbar blocks remain the mainstay of practice.

A randomised double-blinded prospective study by Ryu et al. compared the intraoperative haemodynamic variables and patient reported outcomes of retrobulbar block, sub-tenon block and topical anaesthesia during cataract surgery.  The latter study demonstrated that the mean arterial pressure and heart rate in patients who received a retrobulbar block were significantly higher than those who received a sub-tenon or topical block during and just after the regional block (p<0.05).  However, the retrobulbar group required smaller dosage of patient controlled sedation and fewer supplemental bolus doses than the other groups.  Nevertheless, patients who received a sub-tenon block showed the highest satisfaction scores among the three groups (p<0.05) (1).
Davison et al. compared the effectiveness of topical anaesthesia (with or without the addition of intracameral local anaesthetic) and sub-tenon's anaesthesia in providing pain relief during cataract surgery in a Cochrane systematic review.  Seven studies involving 617 patients with 742 eyes operated on were examined. The overall quality of the studies was not high, with one study triple blind (patient, surgeon and assessor blinded to treatment group) and three others single blind. Three unpaired studies showed that sub-Tenon anaesthesia provided better intra-operative pain relief than topical anaesthesia (pooled weighted mean difference (1.28, 95% CI 0.83to 1.72). The differences in the pain scores were not necessarily clinically significant although statistically significant. The complication of posterior capsule tear and vitreous loss occurred twice as much in the topical group than with sub-Tenon anaesthesia (4.3% versus 2.1%).  The review concluded that Sub-Tenon anaesthesia provides better pain relief than topical anaesthesia for cataract surgery (2).

Nielsen and Allerod carried out a study in which each patient served as their own control.  He compared patients’ subjective experiences of pain with retro/peribulbar, subtenon, and topical anesthesia.  In this prospective, randomised study, 66 patients underwent simultaneous bilateral cataract surgery. Significantly more pain occurred with retro/ peribulbar anesthesia than with the two other methods.  However, during actual surgery pain and discomfort was in the following order: topical > subtenon > retro/peribulbar. Despite this, patients tended to prefer subtenon and topical anesthesia because of the pain associated with the retro/ peribulbar injection (3).

Although topical anaesthesia alone has been shown to be relatively safe and effective, many clinicians use topical anaesthesia in combination with intracameral 1% lidocaine to avoid pain that is often reported in iris manipulation during surgery.  Carino et al. demonstrated that the use of topical tetracaine in addition to intracameral lidocaine resulted in a significant decrease in the patients’ subjective pain experience as well as the surgeon’s satisfaction with the anaesthesia used (4).
It should also be noted that topical and intracameral anaesthesia result in minimal systemic absorption.  One study demonstrated that the topical application of 4% lidocaine resulted in negligible serum concentrations (5).

Unfortunately, there is no one superior anaesthetic technique with regard to phacoemulsification and ultimately the decision will depend on ocular factors such as axial length of the eye, patient co-morbidity, preference of the patient, surgeon and anaesthetist.  It is likely that topical anaesthesia in combination with intracameral lidocaine will become more popular but it is important that careful patient selection is undertaken with the latter form of anaesthesia during cataract surgery.

Mr Adam H. Ross MBChB, MRCOphth, CertMedEd

References.

1.  Ryu JH, Kim M, Bahk JH, Do SH, Cheong IY, Kim YC. A comparison of retrobulbar block, sub-Tenon block, and topical anesthesia during cataract surgery. Eur J Ophthalmol. 2009 Mar-Apr;19(2):240-6.

2.  Davison M, Padroni S, Bunce C, Ruschen H. Sub-Tenon's anaesthesia versus topical anaesthesia for cataract surgery. Cochrane Database Syst Rev. 2007 Jul 18;(3)

3.  Nielsen PJ, Allerod CW: Evaluation of local anesthesia techniques for small incision cataract surgery. J Cataract Refract Surg 1998, 24:1136–1144.

4.  Carino NS, Slomovic AR, Chung F, Marcovich AL: Topical tetracaine versus topical tetracaine plus intracameral lidocaine for cataract surgery. J Cataract Refract Surg 1998, 24:1602–1608.

5.  Bellucci R, Morselli S, Pucci V, Zordan R, Magnolfi G: Intraocular penetration of topical lidocaine 4%. J Cataract Refract Surg 1999, 25:643–647.