Limbal anaesthesia: a new technique for cataract surgery

The development of small sutureless incisions in cataract surgery has led to an increased interest in the use of topical ocular anaesthesia. Topical administration of anaesthetic agents is a very simple technique that can achieve good anaesthesia and eliminate potentially sight-threatening complications related to peribulbar or retrobulbar anaesthesia, such as haemorrhaging, optic nerve trauma or globe perforation.

In a 1995 survey, only 5% of responding members of the American Society of Cataract and Refractive Surgery (ASCRS) reported the routine use of topical anaesthesia for cataract surgery, however, by 1999 this percentage had dramatically risen to 45% (Leaming, 2000). Meanwhile, in 2006, a survey conducted by the European Society of Cataract and Refractive Surgery (ESCRS) reported that topical anaesthesia is the first choice for European cataract surgeons at 56%, but its use varies widely across the continent; ranging from 95% in Norway to 26% in the Netherlands.

Topical anaesthesia: the long & short of it

Inversely, excessive and repeated application of anaesthetic may have a toxic effect on the corneal epithelium. In some cases, this keratopathy can jeopardise intraoperative visibility and make surgery more difficult, while in others it may cause discomfort during the early postoperative period, limit prompt visual recovery or reduce lacrimation and even, on rare occasions, lead to serious keratopathy.

Furthermore, there is a widespread conviction that, in order to increase the efficacy of topical anaesthesia, the intracameral use of nonpreserved lidocaine 1%, as proposed by Gills in 1995, is appropriate: this technique is quite widespread, though not globally accepted (56% of ASCRS survey respondents admitted to using intracameral lidocaine). It must, however, be noted that some researchers have not found pain differences between groups of patients undergoing cataract surgery with topical anaesthesia in the presence or absence of intracameral lidocaine. Moreover, it is possible that the use of intracameral anaesthetic agents could be toxic to the endocular structure. Its effect is not completely clear yet, and we do not have long-term follow-up studies of endothelial cell counts and morphological analyses that can confirm the non-toxicity of intracameral anaesthesia. From our literature research, we have found that some authors note reduced visual acuity and contrast sensitivity during the early hours after surgery in cases where intracameral anaesthesia has been used, whereas others have reported transient visual loss in patients receiving intracameral anaesthetics.

The alternatives

The limitations of topical anaesthesia have inspired many authors to study alternative surface anaesthetic techniques. For example, the topical administration of lidocaine hydrochloride 2% gel or anaesthesia with a modified sponge positioned preoperatively and intraoperatively. These techniques for cataract surgery can be considered an evolution in topical anaesthesia, as they permit good levels of anaesthesia, avoid the multiple administration of anaesthetics and thus reduce the incidence of toxic effects on the cornea. The fact that they are not widely used is probably tied to the added complexity associated with their mode of application when compared with standard topical anaesthesia.

The limbal anaesthesia technique

A few years ago, we began to routinely use a method called "limbal anaesthesia" for cataract surgery. It consists of applying a cellulose ophthalmic sponge soaked in preservative-free lidocaine hydrochloride 4% to the perilimbal area for 45 seconds immediately prior to surgery.