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Ocular Anesthesia for Small Incision Cataract Surgery

Samuel Masket

Introduction

Traditional methods of local ocular anesthesia for cataract surgery have employed injection of anesthetics to the periorbital region. It is well recognized that regional infiltration can produce ocular anesthesia, ocular akinesia, orbicularis akinesia, and varying degrees of amaurosis. However, recent trends strongly indicate that only ocular anesthesia is necessary for routine small incision cataract surgery The 1997 American Society of Cataract and Refractive Surgery member survey for the year 1996 suggests that roughly 15 percent of surgeons employ non-injection anesthesia (topical with or without intracameral agents) routinely.1 Nevertheless, the great majority of surgeons continue to use anesthetic injections with some degree of risks, that include damage to the globe, optic nerve, and periocular structures, and central nervous system (CNS) toxicity including brainstem anesthesia, apnea, and death. Very rarely, the patient may sustain bilateral ocular anesthesia as a result of anesthetic spread through the cavernous sinus. Moreover, with anesthetic injection, there is the potential for cosmetic blemish of the lids and conjunctiva. It is worth noting that patients often rate the quality of their cataract surgery by how the eye looks as well as how the eye sees during the early postoperative period.

The risks of periorbital anesthetic injections are of some consequence, in that the overall occurrence rate for retrobulbar hemorrhage is in the vicinity of 1 percent of all cases, the likelihood increases with long needles and intraconal injection.2 Furthermore, ocular penetration and optic nerve damage are not terribly rare. The risks of those maloccurrences increase in patients who are uncooperative for injection, those with high myopia, those with prior scleral buckling surgery, and when the injections are administered by non-ophthalmologists. Additionally, no needle types, injection sites, or injection styles are immune to the risk for damage to the globe or other orbital structures.3–5

Another issue regarding the blind passage of sharp needles into the orbit concerns those patients on anticoagulant medications or those with naturally occurring coagulopathies. It should be obvious that these patients are at greater risk for periocular hemorrhage with needle injection, but often the medical necessity for anticoagulation dictates that patients remain on treatment during the perioperative period. Often, the systemic risk to cessation of anticoagulant treatment is greater than the risk of intraoperative bleeding. Indeed, the published guidelines for cataract surgery in the United Kingdom suggest that cataract surgery should proceed up to an INR (International

Normalized Ratio) of 4.0 for patients taking Coumadin. It is evident that non-injection forms of local anesthesia are safer for anticoagulated patients.

Additional consequences of periocular anesthetic include an inability of the patient to move the eye during and after surgery. While it was once considered essential that the eye be fully still for safe surgery, it is now recognized that purposeful eye movements, on command, can benefit the progress of surgery. As an example, in cases with narrow palpebral fissures, the eye can be moved to facilitate incisions, etc. A further consequence of regional anesthetic infiltration is amaurosis. As a result, the patient cannot see to fixate a target. However, with topical/intracameral anesthesia, the patient can be asked to follow a light source or other visual target to help fixate the globe in a satisfactory position for surgery.

Movement away from periocular injection toward topical methods of ocular anesthesia is natural, given the overall changes in small incision cataract surgery that have progressed to outpatient surgery with methods that allow for immediate ambulation, rapid return to a full lifestyle, and stable optical results of surgery within days.6 The immediate use of the eye after cataract surgery is possible only with topical/intracameral methods and is in keeping with the concepts of modern surgery.

Topical anesthesia resurfaced in this decade as a useful tool after Fichman’s suggestion regarding the use of tetracaine 0.5 percent applied to the eye as the only anesthetic for cataract surgery.7 Other agents, such as bupivacaine and lidocaine have been popularized because of a reduced tendency to cause corneal epitheliopathy and to have a longer period of action as compared with tetracaine. However, patients are not universally comfortable with topical anesthesia as the only agent. Many surgeons employ small amounts of intravenous, oral, or sublingual sedation as an adjunct. However, in 1995 Gills suggested the routine use of intracameral non-preserved lidocaine in addition to topical anesthesia with or without systemic sedation,8 although the concept had been mentioned earlier by Fichman who considered intraocular tetracaine for use in difficult case situations. Safety and efficacy of intracameral lidocaine has been further established by Koch9 and Masket with Gokmen in separate studies.10 In the latter investigation, approximately 40 percent of more than 300 patients receiving only topical anesthesia required intraoperative conversion to a deeper level of local anesthesia, whereas fewer than 1 percent of 300 cases receiving intracameral lidocaine had need for an additional local anesthetic method. In the same study, safety was measured by comparing the degree of corneal edema on the first postoperative day between the two groups, a reduced likelihood for corneal edema was associated with the use of intracameral nonpreserved lidocaine hydrochloride 1 percent, but this finding may be related to the use of chop style phacoemulsification for the latter group. Nevertheless, based upon the early postoperative appearance of the cornea, nonpreserved lidocaine is seemingly nontoxic although Koch reports reduced contrast sensitivity and visual acuity in the first few hours after surgery.

Other methods to provide ocular anesthesia for cataract surgery without the risks of blind pass, sharp needle orbital injection have evolved during the same era as the movement to topical anesthesia. Posterior sub-Tenon’s infiltration employs a blunt

•Central nervous system anesthesia

•Apnea

•Unintended bilateral ocular anesthesia

•Damage to extraocular muscles/diplopia

•Aesthetic blemish

TABLE 30.2 Advantages of topical/intracameral anesthesia

•Avoids pain, blemish and risk of injection anesthesia

•Allows immediate useful vision after surgery

•Eliminates need for patch after surgery

•Reduces anxiety and/or heavy sedation associated with injection anesthesia

•Compatible for patients on anticoagulants

•Patients can aid surgeon by moving eye for favorable exposure

TABLE 30.3 Contraindications to topical/intracameral anesthesia

Relative

•Language barrier

•Anticipated difficult surgery

•Poorly cooperative patient

Absolute

•Total deafness

•Coarse nystagmus

Varying with the experience of the surgeon, certain conditions may contraindicate the use of topical/intracameral anesthesia (Table 30.3). Given the ability to move the eye, the patient can aid in the surgery or create significant obstacles, cataract surgery under topical/intracameral anesthesia is, by necessity, interactive. Poor patient cooperation is a relative contraindication, as is the inability of the surgeon and patient to adequately communicate in the same language. Often, an interpreter or bilingual family member can be present in the operating theater in order to facilitate surgery without need for injection anesthesia. However, absolute congenital deafness with speaking difficulty is an absolute contraindication, since the patient may become disoriented under the surgical drapes and cannot be expected to communicate by the usual means of lip reading or sign language, patients of this nature often require general anesthesia. Ocular conditions may also act as relative or absolute contraindications, cataracts too dense to allow fixation on the microscope light, potentially complicated surgery (preoperative zonulysis, etc.), and nystagmus are common examples. Nevertheless, the huge majority of patients may safely experience small incision cataract surgery under topical/intracameral anesthetic with very limited sedation.

Phacoemulsification 444

Methods

The author prefers the use of lidocaine HCl 4.0 percent nonpreserved for topical anesthetic. It is long acting and nonmucogenic (previous experience with 0.75% bupivacaine HCl suggests that it causes undesired mucus production.) Intracameral anesthesia is achieved with unpreserved lidocaine HCl 1.0 percent. Some surgeons advocate diluting the intracameral agent with balanced salt solution (BSS) solution in order to raise the pH and reduce the mild discomfort associated with anterior chamber instillation.

1.Administer topical proparacaine HCl 0.4 percent to initiate anesthesia with little sting. Administer dilating agents (cyclopentylate or tropicamide and phenylephrine 2.5%), topical antibiotics, a topical non-steroidal anti-inflammatory drug (NSAID), and lidocaine HCl 4.0 percent four times at five minute intervals prior to surgery.

2.After the patient is brought into the theater, several drops of the 4.0 percent lidocaine are administered prior to the sterile “prep”. The latter begins with instillation of two drops of half strength Betadine solution (not Betadine scrub) directly to the operative eye. At this time, very small amounts of intravenous sedation may be given, depending upon the mental and medical status of the patient, the anxiety of the surgeon, and the observations of the anesthetist or equivalent. The author generally asks that 0.5 mg to 1.0 mg of midazolam HCl be administered IV.

3.During the draping process communicate with the patient about the operative process. Tell them that they will feel slight pressure from the lid speculum and that they will need to fixate on the light of the microscope. Tell them that requests to look up, down, etc. should be achieved by moving the eye and not the head. Reassure them that they will feel no pain.

4.Begin surgery with the microscope light at low levels of illumination, sufficient only to perform a paracentesis. Place 0.2 cc of nonpreserved lidocaine HCl in the anterior chamber and follow that with the viscoelastic of choice. The anesthetic will be washed out as the viscoagent fills the chamber if the lip of the sideport is depressed as the viscoelastic is injected. Slowly increase the microscope light and perform the clear corneal incision. Continue with routine surgical procedure.

5.Generally, no further anesthesia is necessary. However, in situations with prolonged surgery or very sensitive patients, additional intracameral anesthetic may be administered for complaints of “pressure” or intraocular pain. For surface discomfort, the conjunctiva may be swabbed with a pledget of any sterile topical anesthetic, but care should be taken to avoid placing the agent near or in the incision if it contains preservatives. Additionally, small increments of intravenous sedation can be added as may be (rarely) necessary.

6.In the very unlikely case that the patient cannot tolerate the microscope light even at low illumination and continues to squeeze the lids against the speculum, additional doses of IV medicine could be given until the intracameral anesthetic is administered. In author’s observations, once the eye has received the intracameral agent, all lid squeezing and signs of anxiety or discomfort abate rapidly. However, in extreme situations or should an operative complication occur that will significantly prolong

surgery, one can stop surgery, given a self-sealing incision, pressurize the eye to normal, and administer deep sub-Tenon’s local anesthetic with a blunt cannula (Fig. 30.1) through a conjunctival buttonhole entry in the superior or inferior nasal quadrant.

Prior to incising the conjunctiva, a pledget of local anesthesia may be placed on the area for a few moments. The cannula should reach the retrobulbar space with ease if the buttonhole opening includes Tenon’s capsule. Only 2.0 cc of local agent is necessary, given direct access to the muscle cone. Relative amaurosis will be achieved in a matter of seconds, and, with strong local agents, akinesia can be established in a few minutes.

References

1.Learning DV: Practice styles and preferences of ASCRS members: 1996 survey. J Cataract Refract Surg 23:527–35, 1997.

2.Cionni R, Osher R: Retrobulbar hemorrhage. Ophthalmology 98:1153–55, 1991.

3.Duker JS, Belmont JB, Benson WE et al: Inadvertent globe perforation during retrobulbar and peribulbar anesthesia. Ophthalmology 98:519–26, 1997.

4.Hay A, Flynn HW Jr, Hoffman JI et al: Needle penetration of the globe during retrobulbar and peribulbar injections. Ophthalmology 98:1017–24, 1991.

5.Grizzard WS, Kirk NM, Pavan PR et al: Perforating ocular injuries caused by anesthesia personnel. Ophthalmology 98: 1011–16, 1991.

6.Masket S, Tennen DG: Astigmatic stabilization of 3.0 mm temporal clear corneal cataract incisions. J Cataract Refract Surg 22(10):1451–55, 1996.

7.Fichman RA, Fine IH, Grabow HR: Clear-corneal Cataract Surgery and Topical Anesthesia

Thorofare: Slack Inc. 1993.

8.Gills JP, Cherchio M, Raanan MG: Unpreserved lidocaine to control discomfort during cataract surgery using topical anesthesia. J Cataract Refract Surg 23:545–50, 1997.

9.Koch PS: Anterior chamber irrigation with unpreserved lidocaine 1% for anesthesia during cataract surgery. J Cataract Refract Surg 23:551–54, 1997.

10.Masket S, Gokmen F: Efficacy and apparent safety of intracameral lidocaine as a supplement to topical anesthesia. J Cataract Refract Surg 1998 (in print).

11.Stevens JD: A new local anaesthesia technique for cataract extraction by one quadrant subTenon’s infiltration. Br J Ophthalmol 76:670, 1992.

12.Greenbaum S Anesthesia in cataract surgery. In Greenbaum S (Ed): Ocular Anesthesia, Philadelphia: WB Saunders, 1–55, 1997.

13.Fukasaku H, Marron JA: Pin-point anesthesia—a new approach to local ocular anesthesia. J Cataract Refract Surg 20:468, 1994.

Section VI

Phakonit

31.Phakonit

32.Microphaco: Concerns and Opportunities

33.Ultrasmall Incision Bimanual Phaco Surgery and Foldable IOL

34.Corneal Topography in Phakonit with a 5 mm Optic Rollable IOL

35.Phakonit with the Acritec IOL