The first modern application of topical anesthetics was Koller’s use of cocaine in 1884. Since then, synthetic drugs have become available; cocaine is no longer used because of the potential risk of adverse effects and drug abuse. Tetracaine, 0.5% or 1% (amethocaine), and proparacaine, 0.5%, are short-acting (20 minutes) drugs and are the least toxic of the regional and topical anesthetics to the corneal epithelium. Lidocaine, 4%, for injection can be used topically, as can lidocaine jelly, 2%. Bupivacaine, 0.5% and 0.75%, has a longer duration of action but an increased risk of associated corneal toxicity.
The aim of topical anesthetics is to block the nerves that supply the superficial cornea and conjunctiva—namely, the long and short ciliary nerves. Patients should be warned that they will experience some stinging upon application of the drops onto the surface of the cornea.
Topical anesthetics may be combined with subconjunctival anesthetics. Such combinations are well tolerated by patients and allow subconjunctival and scleral manipulations to be carried out. The surgeon can use both topical and sub-Tenon anesthesia initially. Alternatively, topical anesthesia can be achieved and, if not sufficient, it can be supplemented intraoperatively with a sub-Tenon infusion of anesthetic using a blunt cannula.
In a retrospective series involving a large sample size, application of lidocaine, 2%, gel before povidone-iodine preparation was one of the potential risk factors for acute-onset endophthalmitis after temporal clear cornea incision phacoemulsification, but it did not significantly alter rates of endophthalmitis after intravitreal injection.
Intraocular lidocaine has been used to provide analgesia during surgery. The solution used is 0.3 mL of 1% isotonic nonpreserved lidocaine administered intracamerally. No adverse effects have been reported, except for possible transient retinal toxicity when lidocaine was injected posteriorly in the absence of a posterior capsule. Intracameral lidocaine obviates the need for intravenous and regional anesthetic supplementation in most patients. Adequate anesthesia is obtained in approximately 10 seconds. As with topical techniques, patient cooperation during surgery is desirable. Contrasting studies have shown no difference in the degree of cooperation regardless of whether intracameral lidocaine was used as a supplement to topical anesthetics. Because of unreliable patient cooperation, topical and intracameral anesthetics should be used cautiously, if at all, in patients with deafness, dementia, and severe photophobia.
Peribulbar and retrobulbar anesthesia
As stated previously, a mixture of lidocaine and bupivacaine in equal ratio is commonly used for peribulbar or retrobulbar anesthesia. This can be supplemented with hyaluronidase depending on technique and surgeon preference. Before injecting, it is important to pull back on the plunger to ensure that no blood or clear fluid is aspirated into the needle hub. The presence of blood indicates possible intravascular entry, where injection could lead to cardiac arrhythmia. Aspiration of clear fluid suggests the presence of CSF, meaning injection could lead to respiratory depression and seizures. The latter is more likely with the retrobulbar technique. For further discussion of peribulbar and retrobulbar anesthesia and other techniques, see BCSC Section 11, Lens and Cataract.
Crandall AS. Anesthesia modalities for cataract surgery. Curr Opin Ophthalmol. 2001; 12(1):9–11.
Kansal S, Moster MR, Gomes MC, Schmidt CM Jr, Wilson RP. Patient comfort with combined anterior sub-Tenon’s, topical, and intracameral anesthesia versus retrobulbar anesthesia in trabeculectomy, phacotrabeculectomy, and aqueous shunt surgery. Ophthalmic Surg Lasers. 2002;33(6):456–462.
Mindel JS. Pharmacology of local anesthetics. In: Tasman W, Jaeger EA, eds. Duane’s Foundations of Clinical Ophthalmology. Vol 3. Philadelphia: Lippincott Williams & Wilkins; 2006: chapter 35.
Excerpted from BCSC 2020-2021 series: Section 2 - Fundamentals and Principles of Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.