Regional anesthesia for ophthalmic surgery
The trend towards local anaesthesia in preference to general anaesthesia for ophthalmic surgery continues worldwide. This is driven by improved surgical technology, reduced operating times and improvements in anaesthetic techniques. Ophthalmic local anaesthetic techniques can be broadly classified as topical or regional. Regional anaesthesia falls into three main categories: retrobulbar (intraconal), peribulbar (extraconal) and sub-Tenon’s (episcleral) techniques.
Choice of anesthetic technique
In the author’s institution, over 98% of adult cataract surgery and 95% of vitreo-retinal surgery is performed under local anaesthesia, which is almost exclusively sub-Tenon’s block. A one-year national survey of current practices for cataract surgery conducted in the UK in 2003 1 indicated that sub-Tenon’s block was the most common local anaesthetic technique, being used in 43% of cataract surgeries (up from 7% in 1996), with 31% peribulbar and 21% topical. Local anaesthetic techniques are suitable for the majority of ophthalmic surgical procedures including: cataract surgery, vitreo-retinal surgery, trabeculectomy, adult strabismus surgery, panretinal photocoagulation, optic nerve sheath fenestration, long term postoperative pain management and therapeutic delivery of drugs.
Contra-indications to local anaesthesia are relatively few. Absolute contra-indications would include: patient refusal, inability to co-operate and infection at the injection site. Careful consideration is required in patients who are unable to lie flat, are profoundly deaf or have a marked head tremor. General anaesthesia may be preferable in these cases.
Retrobulbar and peribulbar techniques are well described elsewhere. See sub-Tenon’s block for a description of that technique.
One of the major advantages of local anaesthesia is the avoidance of general anaesthesia. There are, however, some disadvantages of local techniques, which include the following:
Retained visual sensations. Patients having cataract surgery under any local technique report a variety of visual sensations 2-5 including flashes of light, colours, movements and surgeon’s fingers. These phenomena appear to not significantly differ between retrobulbar, peribulbar, sub-Tenon and topical techniques. Most patients are unconcerned or even enjoy the phenomenon, but up to 16% interpret the experience as unpleasant. 2 It is therefore useful to warn patients preoperatively.
Optic neuropathy. Retrobulbar, peribulbar and sub-Tenon’s techniques have all been shown to produce a temporary fall in ocular pulse amplitude. 6 This occurs shortly after block insertion and lasts for about 10 minutes before returning to normal, 7-9 although the clinical significance is uncertain. The aetiological mechanism is unclear, but it has been postulated that it may reflect a drop in retinal perfusion due to raised intraocular pressure. Alternatively, local anaesthetic-induced vasoconstriction may contribute because the fall in pulse amplitude can occur in the absence of an intraocular pressure rise. Although it is very rare to cause a clinical problem, it may be more of a concern for patients with pre-existing retinal hypoperfusion and patients having non-intraocular surgery, where there is no incision in the globe, which could otherwise reduce intraocular pressure and restore perfusion.
Trauma to the globe and surrounding structures. Injuries include scleral perforation, optic nerve damage, retrobulbar haemorrhage and extraocular muscle paresis.
Orbital Cellulitis. Infection following regional orbital blocks is rare, possibly because of the antibactrial action of local anaesthetics such as lignocaine and bupivacaine.
Regional techniques all have the potential to produce similar complications; the main difference is in their incidence. In a study by Eke in 2007 of 375,000 patients having cataract surgery in the UK, of whom 161,000 had a sub-Tenon block, the reported incidence of sub-Tenon block related sight-threatening complications was less than 0.6 per 10,000 cases. 1 This figure compares favorably to peribulbar (2.9 per 10,000) and retrobulbar (4.5 per 10,000) techniques. This was further supported in a study by El-Hindy et al. in 2009, which included 26,045 sub-Tenon blocks. 10 They found a 60% reduction in the incidence of serious complications with sub-Tenon block in comparison to peribulbar anesthesia: 5 per 10,000 in the sub-Tenon block group in comparison to 12 per 10,000 in the peribulbar group. However, minor complications in the sub-Tenon group such as chemosis and sub-conjunctival hemorrhage (both 2%) were more common than in the peribulbar group.
In studies comparing topical with regional anaesthesia, most patients prefer a regional block. 11, 12 Studies comparing sub-Tenon’s techniques with topical anaesthesia indicate that sub-Tenon’s block provides superior analgesia, 13 is associated with a lower posterior capsule rupture rate 14 and higher patient satisfaction. 15
These data indicate that sub-Tenon block is safer than sharp needle techniques. Furthermore, because sub-Tenon's block is associated with fewer intraoperative surgical complications compared with topical techniques, published evidence to date supports sub-Tenon's block as the anaesthetic of choice for ophthalmic surgery.
1. Eke T, Thompson JR. Serious complications of local anaesthesia for cataract surgery: a 1 year national survey in the United Kingdom. Br J Ophthalmol 2007;91: 470-5.
2. Prasad N, Kumar CM, Patil BB, et al. Subjective visual experience during phacoemulsification cataract surgery under sub-Tenon's block. Eye (Lond) 2003;17: 407-9.
3. Rengaraj V, Radhakrishnan M, Au Eong KG, et al. Visual experience during phacoemulsification under topical versus retrobulbar anesthesia: results of a prospective, randomized, controlled trial. Am J Ophthalmol 2004;138: 782-7.
4. Tan CS, Au Eong KG, Kumar CM. Visual experiences during cataract surgery: what anaesthesia providers should know. Eur J Anaesthesiol 2005;22: 413-9.
5. Wickremasinghe SS, Tranos PG, Sinclair N, et al. Visual perception during phacoemulsification cataract surgery under subtenons anaesthesia. Eye (Lond) 2003;17: 501-5.
6. Findl O, Dallinger S, Menapace R, et al. Effects of peribulbar anesthesia on ocular blood flow in patients undergoing cataract surgery. Am J Ophthalmol 1999;127: 645-9.
7. Kim SK, Andreoli CM, Rizzo JF, 3rd, et al. Optic neuropathy secondary to sub-tenon anesthetic injection in cataract surgery. Arch Ophthalmol 2003;121: 907-9.
8. Luscavage LE, Volpe NJ, Liss R. Posterior ischemic optic neuropathy after uncomplicated cataract extraction. Am J Ophthalmol 2001;132: 408-9.
9. Pianka P, Weintraub-Padova H, Lazar M, et al. Effect of sub-Tenon's and peribulbar anesthesia on intraocular pressure and ocular pulse amplitude. J Cataract Refract Surg 2001;27: 1221-6.
10. El-Hindy N, Johnston RL, Jaycock P, et al. The Cataract National Dataset Electronic Multi-centre Audit of 55,567 operations: anaesthetic techniques and complications. Eye (Lond) 2009;23: 50-5.
11. Boezaart A, Berry R, Nell M. Topical anesthesia versus retrobulbar block for cataract surgery: the patients' perspective. J Clin Anesth 2000;12: 58-60.
12. Friedman DS, Reeves SW, Bass EB, et al. Patient preferences for anaesthesia management during cataract surgery. Br J Ophthalmol 2004;88: 333-5.
13. Chittenden HB, Meacock WR, Govan JA. Topical anaesthesia with oxybuprocaine versus sub-Tenon's infiltration with 2% lignocaine for small incision cataract surgery. Br J Ophthalmol 1997;81: 288-90.
14. Davison M, Padroni S, Bunce C, et al. Sub-Tenon's anaesthesia versus topical anaesthesia for cataract surgery. Cochrane Database Syst Rev 2007: CD006291.
15. Ruschen H, Celaschi D, Bunce C, et al. Randomised controlled trial of sub-Tenon's block versus topical anaesthesia for cataract surgery: a comparison of patient satisfaction. Br J Ophthalmol 2005;89: 291-3.