In response to comments on limbal anaesthesia for clear cornea phacoemulsification

Abstract

Editor, First of all, we would like to thank correspondents Rai and Singh Sethi for their appreciative comments regarding this innovative technique. However, we would like to point out that, in our opinion, the proper placement of limbal anaesthesia (LA) would be as an evolution of topical anaesthesia. In fact, the patient's level of analgesia and the safe surgery achieved with this method are similar to those obtained with topical anaesthesia. This is demonstrated by a randomized, double-blind study we have recently completed and which we plan to publish shortly. With LA, patient co-operation is excellent because we instil one drop of anaesthetic solution outside the operating room immediately before the patient is brought in for surgery. This permits sufficient surface anaesthesia for application of the lid speculum and for application of the sponge soaked in preservative-free lidocaine can be applied for 45 seconds. Limbal anaesthesia provides of analgesia of the entire circumference of the limbus and of every quadrant of the cornea, similar to that obtained with topical anaesthesia. Moreover, LA ensures adequate iris and ciliary body anaesthesia. The precise mechanism of this anaesthesia is not completely understood: corneal anaesthesia results from blocking the pericorneal and annular plexus, whereas it is likely that the penetration of anaesthetic agents through the corneal and conjunctival−scleral route results in iris and ciliary body anaesthesia (Ahmed & Patton 1985; Shoenwald et al. 1997). In fact, in our experience, the patient does not feel any pain during contact with the main point of entry or during the side-port incisions, and it is possible to execute the entire procedure safely. Therefore, LA completely eliminates the need for repeatedly instilling the anaesthetic solution, and must be preceded by a single drug application in order to instil the disinfectant and apply the blepharostat. A similar experience was presented by Lanzetta et al. (2000), who proposed perilimbal topical anaesthesia without the addition of anterior chamber irrigation with lidocaine in routine clear corneal cataract surgery; they demonstrated that, with this new anaesthesia, it is possible to achieve a sufficient level of anaesthesia to perform surgery safely. Consequently, the main feature of limbal anaesthesia is the fact that it further simplifies preoperative procedures, and that the surgeon can be confident that an adequate quantity of anaesthetic has been administered, avoiding the toxic effects caused by multiple or excessive administration of the drug. In our operating rooms, LA has now become the anaesthesia of choice in surgery of the anterior segment. We also use it routinely in trabeculectomies and are conducting a randomized double-blind study comparing LA with peribulbar anaesthesia in phacotrabeculectomy procedures.