CHAPTER 10 Anesthesia for cataract surgery
The 1990s saw a change from large incision cataract surgery to the modern small incision phacoemulsification technique. Previously, large incision surgery led most surgeons to demand an immobile eye (akinesia) in addition to a pain-free eye (anesthesia). The small, self-sealing ‘phaco’ incision means that akinesia is no longer mandatory, and this makes ‘minimal anesthesia’ techniques possible.
Phacoemulsification can be performed using general anesthesia (GA), or local anesthesia (LA). Oral or intravenous sedatives can be used with LA, if desired. There are several LA techniques, including sharp needle injections, infiltration using a blunt cannula, and topical anesthesia (eye-drops). The technique chosen will depend on a variety of factors, including: surgeon and patient preference, cultural expectations, special circumstances related to either the eye, the patient or the planned surgery, cost, risk, and the needs of the service provider. In many countries, outpatient surgery using LA is standard. Actual practice varies widely, both within and between countries.
General anesthesia (GA)
Any type of cataract surgery can be performed using general anesthesia. The time, risk, and resources required mean that GA is often reserved for those cases in which LA is inappropriate, e.g. children, patients with dementia or extreme anxiety. Some surgeons may prefer GA to LA, but it is unusual for the cataract operation itself to require a GA.
Local anesthesia (LA) techniques
Several techniques of LA have been described for cataract surgery. There are three main categories: (i) sharp needle blocks (retrobulbar, peribulbar)1, (ii) blunt cannula blocks (subTenon’s)2, and (iii) minimal anesthesia (topical, topical-intracameral)3. These techniques are compared in Table 10.1. Other techniques have been described, including subconjunctival LA, and subTenon’s LA using a sharp needle. For any LA procedure, the patient should be warned what to expect beforehand. If sedation is not used, most patients find it reassuring to hold the hand of an assistant, who also monitors the patient during surgery. Guidelines for safe practice have been published4,5.
LA agents
New anesthetic agents have shown little advantage over established agents. Lidocaine continues to be popular for LA cataract surgery because of rapid onset, low toxicity, and suitable duration of effect. Bupivacaine may be myotoxic to extraocular muscles. Hyaluronidase speeds the diffusion of injectate through tissues, and may improve quality of LA blocks. Severe orbital inflammation has been described with animal-derived hyaluronidase, including some cases of blindness. In recent years, hyaluronidase from a recombinant DNA source has become commercially available, hopefully with an improved safety profile. Topical anesthetic eye-drops include lidocaine, proxymetacaine (less stinging, probably weaker anesthetic effect), and tetracaine (probably stronger anesthetic effect).
Sharp needle blocks
Retrobulbar and peribulbar LA injections1 (Figs 10.1, 10.2) give excellent akinesia and analgesia, although they are associated with sight-threatening and life-threatening complications. The needle may penetrate the globe or optic nerve, and this can result in blindness. Long myopic eyes, particularly those with a staphyloma, are at particular risk of this complication. If the needle penetrates the meninges around the optic nerve, the LA may enter the subdural space and track back to the brainstem; brainstem anesthesia may present with apnea, fitting, unstable blood pressure, and possibly death1,6. While these complications are rare, they are of course devastating. Therefore, it is recommended that these techniques are only used after suitable training, consideration of the anatomy and eyeball size/shape for each case, and with back-up available in case of an inadvertent brainstem injection1,4,5. Even in the best hands, these complications can occur with sharp needle blocks1
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