Is intracameral anesthetic application the final solution to topical anesthesia for cataract surgery?

The most effective method of applying local anesthesia during cataract removal has been under investigation for a long time.1 A recent editorial2 divides local anesthesia techniques into “injectional” and “topical” procedures: Injectional: retrobulbar, peribulbar, sub-Tenon's, subconjunctival. Topical: Eyedrop application; sponge anesthesia, eyedrops plus intracameral application; gel application. Although retrobulbar and peribulbar anesthesia have been the preferred techniques for several decades, new techniques have emerged that lower or eliminate the risks of needle injection such as perforation, direct damage to the orbital structures, and central nervous system anesthesia spread. Topical anesthesia has become possible primarily because of minimally invasive surgery with small self-sealing tunnel incisions, phacoemulsification, and foldable intraocular lens implantation. The use of clear corneal incisions, which avoid conjunctival disinsertion and scleral diathermy, has made topical anesthesia even more effective. The technique has also been advocated for scleral tunnel incisions.3,4 To control the discomfort of patients during cataract surgery using topical anesthesia, intracameral injection of anesthesia has been recommended.5,6 Several articles in this issue look at whether intracameral anesthetic application is a satisfactory and appropriate solution to topical anesthesia for cataract surgery. Intracameral injection of anesthetic agents is responsible for the recent success of topical anesthesia. The superiority of topical plus intracameral anesthesia over pure topical application has been demonstrated recently.7 However, since the authors of this study used only 2 drops of 0.5% tetracaine twice, it is not surprising that the topical application alone was not effective. As demonstrated by Behndig and Lindén,8 longer topical application of lidocaine increases aqueous humor concentration. As a low level of intraocular anesthetic concentration is a major factor in pain during surgery (Bellucci et al.), optimal application methods are mandatory. Obviously, analgesia depends on the intraocular penetration of the topical anesthetic agent. A new method of topical administration, lidocaine hydochloride 2% gel, is investigated in 3 articles in this issue. The administration of lidocaine 2% gel resulted in pain scores similar to those with intracameral anesthesia (Koch), revealed no significant toxicity to the ocular surface (Barequet and coauthors), and also provided prolonged lubrication (Assia et al.), an interesting side effect of topical anesthesia during surgery. The efficacy of topical and topical plus intracameral anesthesia could be re-evaluated with this new form of anesthetic administration. The safety of intracameral anesthesia is evaluated by Elvira et al. Their study showed that endothelial cell loss after the use of 0.3 mL of lidocaine 1% (5.4% after 1 month, 5.9% after 3 months) is comparable to that found after cataract extraction with other types of local anesthesia. However, recent reports suggest that ophthalmic surgeons should be aware of the potential for endothelial cell injury if anesthetic agents enter or are injected into the eye.9,10 This is not surprising because the intraocular concentration of the local anesthetic agent after an intracameral injection can be 250 times higher than the concentration after topical application.8 The peer-reviewed literature on intracameral anesthesia usually evaluates only short-term effects on the corneal endothelium.11 A randomized, prospective study comparing endothelial cell loss for different anesthesia techniques after cataract extraction in human eyes by the same surgeon over a long period would be helpful to prove the local safety of intracameral injection of an anesthetic agent. One conclusion can already be made from the article by Wirbelauer et al. A commonly used concentration of intracameral anesthesia (0.5 mL of lidocaine 1%) revealed no systemic therapeutic concentrations, which has been a concern of some physicians (surgeons and anesthesiologists). The studies of topical and intracameral application of local anesthetics in this issue demonstrate the ongoing effort to improve our anesthesia methods and to minimize or even exclude any risk of intraocular structure injury from drug delivery during cataract surgery. The appropriate application of local anesthesia is still being explored to provide the most beneficial application for the patient.