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Anesthesia for Intraocular Surgery
SURVEY OF OPHTHALMOLOGY VOLUME 46 • NUMBER 2 • SEPTEMBER–OCTOBER 2001
VIEWPOINTS JONATHAN DUTTON AND THOMAS SLAMOVITS, EDITORS
Anesthesia for Intraocular Surgery I. Editorial: Anatomic Considerations in Ophthalmic Anesthesia. Jonathan J. Dutton, MD, PhD II. Topical/Intracameral Anesthesia for Cataract Surgery. S. Akbar Hasan, MD, Henry F. Edelhauser, PhD, and Terry Kim, MD III. Injectional Orbital Anesthesia for Cataract Surgery. Clark L. Springs, MD, and Geoffrey Broocker, MD Abstract. Surgeons must decide on the type of anesthesia to use when performing cataract surgery. These “Viewpoints” articles provide a well-balanced discussion offering the pros and cons of both topical anesthesia and retrobulbar/peribulbar injection. Dr. Dutton gives an overview of both techniques, focusing on the relevant orbital anatomy. Drs. Hasan, Edelhauser and Kim, review the various types of topical anesthesia currently in use, and Drs. Springs and Broocker examine retrobulbar and peribulbar injections. Both techniques are associated with advantages and risks, so each surgeon must decide which technique is best suited for his or her own practice. (Surv Ophthalmol 46:172–178, 2001. © 2001 by Elsevier Science Inc. All rights reserved.) Key words. anesthesia • cataract surgery • peribulbar injection • retrobulbar injection • topical anesthesia
I. Editorial: Anatomic Considerations in Ophthalmic Anesthesia Jonathan J. Dutton, MD, PhD Atlantic Eye & Face Center, Cary, North Carolina, and University of North Carolina, Chapel Hill, North Carolina, USA
Ophthalmic anesthesia has evolved over the decades into a sophisticated art. When properly applied it provides comfort to the patient, allays anxiety, and allows the safe execution of delicate eye surgery. While the retrobulbar block has been a standard for many decades, newer techniques, such as
the peribulbar and sub-Tenon’s blocks, and more recently topical anesthesia, have gained in popularity over the past several years. These less-invasive techniques have been promoted in order to reduce the risks of complications while still achieving adequate patient comfort.15,22,26 Regardless of the specific tech172
© 2001 by Elsevier Science Inc. All rights reserved.
0039-6257/01/$–see front matter
ANESTHESIA FOR INTRAOCULAR SURGERY
nique employed, knowledge of local and regional anatomy is essential in order to achieve the proper levels of sensory and motor blockade with minimal complications.32
Anatomic Complications of Retrobular Block For the retrobulbar and peribulbar blocks, a visual concept of orbital anatomy is critical to avoid injury to vascular and neural structures essential to visual function. Potential complications include globe perforation, optic nerve injury, subarachnoid injection, extraocular muscle injury, and orbital hemorrhage, among others. Globe perforation has been reported in as many as 0.75% of retrobulbar and peribulbar injections.6,8,10,24 Most commonly this involves a tangential penetration in the inferolateral quadrant, and may include penetration of the inferior oblique muscle as well. Retinal detachment and vitreous hemorrhage are common sequellae, with potential for visual loss. The risk of globe perforation is greater when a sharp-pointed, cutting-edge needle is used rather than a blunt retrobulbar needle, although globe perforation has been reported in both cases.12 Careful observation of the globe during needle entry may alert the surgeon or anesthetist to impending globe penetration by rotation of the eye toward the direction of needle entry. The so-called “wiggle test” is also useful in determining if the needle tip has impaled an orbital structure fixed to the eye. In this test, after the retrobulbar needle is in the orbit, but before any anesthetic is injected, the needle is moved from side to side; any rotation of the eye suggests that the sclera, optic nerve, or an extraocular muscle may have been penetrated. Injection of local anesthetic into the eye is a potentially devastating complication. The sclera is only 0.8- to 1.0-mm thick, and it offers little resistance to perforation by a sharp needle. Because the injection is into a closed space, the surgeon should be aware that resistance to fluid injection is elevated. As little as 40 mm Hg of pressure at the plunger head of the syringe can translate into more than 3000 mm Hg of intraocular pressure, enough to rupture the globe. Larger syringes have a greater mechanical advantage and therefore produce greater risk. Injection of anesthetic directly into the optic nerve can result in severe injury and immediate blindness. If the injection pressure is high, the operator should be aware of impending disaster. As mentioned above, if the “wiggle test” is positive, then the operator should withdraw the needle before injection. It is equally important to avoid penetration of the optic nerve sheath, and injection of anesthetic into the subarachnoid space. This compartment contains cerebrospinal fluid (CSF) in communication with
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the subdural intracranial and spinal CSF. Injection of anesthetic into this space may result in sensory blockade of contralateral vision, CNS depression, paralysis, seizures, hypotension, cardiac arrest, and even death.5,14,16,25,27,29 As with direct injection into the optic nerve, the “wiggle test” will be positive, but the increased injection pressure may not be immediately appreciated. Injury to an extraocular muscle may be more subtle, because there is very little resistance to needle penetration. The anterior ciliary arteries originate in the posterior orbit from the ophthalmic artery and penetrate the posterior one-third of the rectus muscles on their conal surface. These vessels run anteriorly and centrally within the muscle bellies and then on the outer surface of the muscle tendons to their points of insertion on the globe. These vessels then penetrate the sclera through emissary canals to supply the ciliary body, iris, and anterior choroidal circulation. The anterior ciliary vessels may be injured by the retrobulbar needle, resulting in retrobulbar orbital hemorrhage or hematoma directly into the muscle itself. The muscles most likely to be injured during needle entry are the inferior oblique or the inferior rectus muscles. While the inferior oblique does not contain ciliary vessels, it is a large and thick muscle that is highly vascular, and its location along the inferolateral globe back to the macula makes it particularly vulnerable to retrobulbar needle entry. Local anesthetics are quite toxic to striated muscle tissue. Inadvertent injection can result in muscle dysfunction ranging from mild and temporary paralysis to marked fibrosis.1 Postoperative muscle dysfunction may be seen even without any clinical evidence of muscle penetration and is the most frequent cause of postoperative strabismus following cataract or scleral buckle procedures.2,4,30,31 We have seen marked severe muscle fibrosis ensuing within days to weeks of such injury. In rare instances the strabismus may be neuropathic in origin due to injury to a cranial nerve near the orbital apex. Orbital hemorrhage is the most common complication of retrobulbar injection, reported in 0.1% to 1.7% of procedures.3,5,11 The orbit is highly vascular and contains numerous arteries and veins, as well as the ciliary vessels within the extraocular muscles. Most of the larger vessels are located in the superior and medial orbit, making these regions more vulnerable to vascular injury. The quadrant most devoid of larger vascular elements is inferolateral, and this is true of both the intraconal and extraconal compartments. Although very few vessels run in the peripheral orbital space, subperiosteal hemorrhage can occur from contact of the needle with the orbital bony walls, and in one case this resulted in blindness.9 While most orbital hemorrhagic events resolve un-
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eventfully, an acute bleed can loculate within the orbital septal fascial systems, producing a compartment syndrome. The resulting optic nerve and superior ophthalmic vein compression may cause visual loss or an excessive rise in intraocular pressure. Retrobulbar injection can also significantly reduce pulsatile ocular blood flow by about 250 l/min.13 This might have the potential to alter intraocular pressure, and it could compromise eyes with borderline blood flow. Hyaluronidase in the anesthetic agent has been reported to produce less reduction in blood flow.
Anatomic Complications of Sub-Tenon’s Block In the sub-Tenon’s block, Tenon’s capsule is elevated from the sclera, and local anesthetic is infused into the sub-Tenon’s/episcleral space. To be most effective, the anesthetic must diffuse back to the posterior globe near the optic nerve. Here the posterior ciliary nerves perforate Tenon’s capsule and pass through Tenon’s space to penetrate sclera (Fig. 1). These nerve branches originate from the ophthalmic division of the trigeminal nerve as the long posterior ciliary nerves, and as non-synapsing fibers passing through the ciliary ganglion, and run forward in the short posterior ciliary nerves. They carry sensory information from the ciliary body, iris, and cornea. In addition, the short posterior ciliary nerves carry post-synaptic parasympathetic motor fibers from the Edinger–Wesphal nucleus to the ciliary body and iris. Thus, placement of anesthetic into the posterior Tenon’s space will provide both sensory and motor blockade to the anterior intraocular structures, supplemented with topical anesthetic to the cornea and conjunctiva. The major potential complications of the subTenon’s block are injury to the sclera and to the cili-
Fig. 1. Sub-Tenon’s infusion with catheter placed beneath Tenon’s capsule. The anesthetic agent is injected and diffuses to the posterior ciliary nerves.
DUTTON ET AL
ary nerves with the perfusing canula or catheter. Penetration of the globe has been reported, and nerve injury can result in pupillary or accommodative abnormalities. Orbital hemorrhage, although rare, has also been reported, presumably from penetration of posterior Tenon’s capsule.
Relevant Orbital Anatomy A detailed knowledge of orbital anatomy is not necessary for the delivery of safe anesthesia during ophthalmic surgery. Indeed, one only needs to have a visual picture of the major anatomic structures and their relationships during ocular movement. This visual, or “eidetic”, image allows the surgeon or anesthetist to navigate the orbit with greater confidence. From an anatomic perspective the orbit can be conceived as having three major compartments, the peripheral space, extraconal space, and intraconal space. The peripheral space is the potential space between periorbita and the orbital walls. It contains only a few vascular and neural elements penetrating bone to enter or leave the orbit. The intraconal space is defined as the conical compartment roughly bounded by the four rectus muscles, from the annulus of Zinn at the orbital apex to their penetration through Tenon’s capsule (Fig. 2). Although there is an extensive system of orbital fascial membranes interconnecting the muscles and suspending them to the orbital walls, nevertheless, the classic concept of an encircling membrane (the intermuscular septum) separating the extraconal from intraconal compartments is a conceptual convenience more than an anatomic reality.7,21 Anesthetic and other fluids can easily diffuse from the extraconal space into the intraconal compartment, which explains the equal efficacy of peribulbar and retrobulbar placement of anesthetic agents28 and the rapid distribution of hemorrhage throughout the orbit. The addition of hyaluronidase to the anesthetic agent may help diffusion across the interlobular septal membranes, thus enhancing the anesthetic effect and reducing the need for supplemental blocks.17 Within the orbit, larger vascular and neural elements are concentrated in the orbital apex, and they diverge as they extend forward. Thus, the greatest density of structures at greatest risk for injury is in the apical one-third of the orbit, approximately 30 to 45 mm behind the orbital rim. This is the region where the ciliary ganglion is located and where cranial nerves 3, 4, and 6 penetrate their respective extraocular muscles. The vortex veins, ophthalmic artery, superior and inferior ophthalmic veins, and the muscular arteries are also concentrated here. However, except for the inferior ophthalmic vein and its venous plexus, and the ciliary ganglion and nerves, most of these structures are situated in the superior
ANESTHESIA FOR INTRAOCULAR SURGERY
175 Fig. 2. Major anatomical structures of the orbit. The intraconal space is defined as the compartment bounded by the four rectus muscles.
half of the orbit. Therefore, a needle inserted into the inferolateral intraconal space will present the lowest risk to these structures. Entry into the superior or superomedial orbit carries the highest risk of anatomic injury. In the posterior orbit, situated just inferior and lateral to the optic nerve, is the ciliary ganglion, where parasympathetic fibers destined for the ciliary body and iris synapse are present. This is the region of the orbit where the motor nerves to the extraocular muscles penetrate the conal surface of the muscles. This region, therefore, in the inferolateral posterior orbit is of major interest for retrobulbar
anesthesia because anesthetic placed here will block both sensory and motor innervation to the eye, as well as visual signals along the optic nerve. Such a block will generally not provide sensory block to the eyelids because these branches of the trigeminal nerve primarily run in the superior extraconal space and within the bony infraorbital canal in the floor. Thus, if eyelid surgery is contemplated, additional regional or local blocks must be given more anteriorly. Of great concern is the central retinal artery, located near the ciliary ganglion and entering the optic nerve on its inferior aspect. This is a relatively large structure in the central cone and has a great
Fig. 3. Shift in the position of orbital structures when the globe is in the upgaze position.
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Surv Ophthalmol 46 (2) September–October 2001
DUTTON ET AL Fig. 4. Shift in the position of orbital structure when the globe is in the downgaze position.
deal of redundancy, coiling along the lateral side of the optic nerve. It therefore presents a significant target for potential injury. The length of the orbit is highly variable, as is the relative location of other anatomic structures. Ketsev et al20 measured the depth of the normal orbit and the position of the ciliary ganglion in cadaver specimens. They showed that the average distance from the inferolateral orbital rim to the apex is 48 mm, with a range of 42 to 54 mm. Similar findings were reported by Karampatakis et al.19 The annulus of Zinn, enclosing the optic nerve, extends 8–9 mm in front of the orbital apex; therefore, this immobile and more vulnerable portion of the nerve can lie as little as 33 mm from the orbital rim in the shortest orbits. Ketsev et al also showed that the average distance from the rim to the ciliary ganglion was 38 mm, with a range of 32–44 mm.20 Using a 40-mm retrobulbar needle, Karampatakis et al found that in
100% of cadaver specimens studied, the needle tip reached the posterior optic nerve, and in nearly 60% (7/12) it significantly pushed against the nerve.18 Even when a 35-mm needle is used, the tip engages the optic nerve sheath in 18% of cases. It is clear, therefore, that in order to ensure a safe approach to the orbital apex and ciliary ganglion, a retrobulbar needle should not exceed 31.5 mm in length.
Anatomy of Ocular Movement Of significant interest to the surgeon or anesthetist delivering retrobulbar anesthesia is the relative shift in position of the major anatomic structures with globe gaze positions. Knowledge of these relationships can allow us to manipulate these structures so as to maximize the safe zones for passage of the retrobulbar needle and to shift certain structures into less vulnerable positions.
Fig. 5. Position of orbital structures and the retrobulbar needle when the globe is in the primary gaze position.
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In the upgaze position, the optic nerve and ciliary ganglion are displaced downward into the inferior orbit, and the inferior oblique muscle is displaced forward toward the orbital rim (Fig. 3).This position lessens the risk of injury to the muscle, and makes it easier to achieve sensory blockade at the ciliary ganglion. However, it puts the optic nerve at greater risk of penetration. In the downgaze position, the optic nerve and ciliary ganglion are displaced upward, and the inferior oblique muscle is shifted backward (Fig. 4). This puts the muscle closer to the orbital floor behind the orbital rim and into the potential path of the retrobulbar needle. However, this is the safest position to prevent injury to the optic nerve. The primary gaze position offers a good compromise between optic nerve and inferior oblique muscle positions (Fig. 5). It also avoids having the patient look directly at the needle, and thus reduces potential apprehension. In this position the retrobulbar needle can be introduced at the inferolateral orbital rim and advanced parallel to the floor to the level of the posterior globe. It must be kept in mind that the posterior globe position depends on many factors and can be highly variable among patients. The relative degree of proptosis or shallowness of the orbit can significantly alter the depth of the globe within the orbit, as can the degree of myopia and globe size.23 The posterior sclera can vary from less than 10 mm behind the orbital rim to more than 18 mm. In patients with orbital diseases, such as Graves’ disease, or in those with marked enophthalmos from trauma, this disparity can be even greater. A careful evaluation of the globe in relation to the orbital rims will help determine the probable depth of the posterior pole. When the advancing retrobulbar needle reaches the posterior surface of the globe, the needle must be directed slightly upward. At this point the bony orbital floor slopes upward to the apex at an angle of about 10 to 15 degrees. In the traditional retrobulbar injection, the needle tip is advanced into the intraconal space between the lateral and inferior rectus muscles to reach the vicinity of the ciliary ganglion. As mentioned above, this region of the orbit is relatively empty of vascular structures and therefore provides relative safety. In the peribulbar block, the anesthetic is injected within the extraconal space without penetrating the muscle cone.
Conclusion It should be clear that the placement of a needle and injection of anesthesia into the orbit is not a procedure to be taken lightly or to be casually performed by the novice. Although the vast majority of
procedures proceed uneventfully, the risks are significant and the potential complications can be devastating. Techniques that minimize these risks are available, both as modifications to the classic retrobulbar block or as one of the newer, less invasive techniques. In the articles that follow this one, a balanced discussion is presented for both retrobulbar injection and topical anesthesia in cataract surgery. In the first discussion, Drs. Hasan, Edelhauser, and Kim review the various types of topical anesthesia currently in use, and they present the in vivo data supporting the use of adjuvant intracameral anesthesia. Drs. Springs and Broocker focus on retrobulbar and peribulbar injections as effective alternatives in cataract surgery. Both approaches are associated with distinct advantages and potential risks, and every surgeon must evaluate for himself or herself the benefits of each technique in their own practice.
References 1. Ando K, Oohira A, Takao M: Restrictive strabismus after retrobulbar anesthesia. Jpn J Ophthalmol 41:23–6, 1997 2. Brown SM, Brooks SE, Mazow ML: Cluster of diplopia cases after periocular anesthesia without hyaluronidase. J Cataract Refract Surg 25:1245–9, 1999 3. Cionni RJ, Osher RH: Retrobulbar hemorrhage. Ophthalmology 98:1153–5, 1991 4. Corboy JM, Jiang X: Postanesthetic hypotropia: a unique syndrome in left eyes. J Cataract Refract Surg 23:1394–8, 1997 5. Davis DB 2nd, Mandel MR: Efficacy and complication rate of 16,224 consecutive peribulbar blocks. A prospective multicenter study. J Cataract Refract Surg 20:327–37, 1994 6. Duker JS, Belmont JB, Benson WE: Inadvertent globe perforation during retrobulbar and peribulbar anesthesia. Patient characteristics, surgical management, and visual outcome. Ophthalmology 98:519–26, 1991 7. Dutton JJ: Clinical and Surgical Orbital Anatomy. Philadelphia, W.B. Saunders Company, 1994, pp 93–111 8. Edge R, Navon S: Scleral perforation during retrobulbar and peribulbar anesthesia: risk factors and outcome in 50,000 consecutive injections. J Cataract Refract Surg 25:1237–44, 1999 9. Girard LJ: Subperiosteal orbital hemorrhage from retrobulbar injection resulting in blindness. Arch Ophthalmol 115: 1085–6, 1997 10. Grizzard WS, Kirk NM, Pavan PR: Perforating ocular injuries caused by anesthesia personnel. Ophthalmology 98:1011–6, 1991 11. Hamilton RC, Gimbel HV, Strunin L: Regional anaesthesia for 12,000 cataract extraction and intraocular lens implantation procedures. Can J Anaesth 35:615–23, 1988 12. Hay A, Flynn HW Jr, Hoffman JI, Rivera AH: Needle penetration of the globe during retrobulbar and peribulbar injections. Ophthalmology 98:1017–24, 1991 13. Hulbert MF, Yang YC, Pennefather PM, Moore JK: Pulsatile ocular blood flow and intraocular pressure during retrobulbar injection of lignocaine: influence of additives. J Glaucoma 7:413–6, 1998 14. Jackson K, Vote D: Multiple cranial nerve palsies complicating retrobulbar eye block. Anaesth Intensive Care 26:662–4, 1998 15. Jacobi PC, Dietlein TS, Jacobi FK: A comparative study of topical vs retrobulbar anesthesia in complicated cataract surgery. Arch Ophthalmol 118:1037–43, 2000 16. Javitt JC, Addiego R, Friedberg HL: Brain stem anesthesia after retrobulbar block. Ophthalmology 94:718–24, 1987 17. Kallio H, Paloheimo M, Maunuksela EL: Hyaluronidase as
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18.
19. 20. 21. 22. 23. 24. 25. 26.
Surv Ophthalmol 46 (2) September–October 2001 an adjuvant in bupivacaine-lidocaine mixture for retrobulbar/peribulbar block. Anesth Analg 91:934–7, 2000 Karampatakis V, Natsis K, Gigis P, Stangos NT: The risk of optic nerve injury in retrobulbar anesthesia: a comparative study of 35 and 40 mm retrobulbar needles in 12 cadavers. Eur J Ophthalmol 8:184–7, 1998 Karampatakis V, Natsis K, Gigis P, Stangos NT: Orbital depth measurements of human skulls in relation to retrobulbar anesthesia. Eur J Ophthalmol 8:118–20, 1998 Katsev DA, Drews RC, Rose BT: An anatomic study of retrobulbar needle path length. Ophthalmology 96:1221–4, 1989 Koornneef L: The architecture of the musculo-fibrous apparatus in the human orbit. Acta Morphol Neerl Scand 15:35– 64, 1977 Leaming DV: Practice styles and preferences of ASCRS members—1998 survey. J Cataract Refract Surg 25:851–9, 1999 Modarres M, Parvaresh MM, Hashemi M, Peyman GA: Inadvertent globe perforation during retrobulbar injection in high myopes. Int Ophthalmol 21:179–85, 1997 Mount AM, Seward HC: Scleral perforations during peribulbar anaesthesia. Eye 7:766–7, 1993 Nicoll JM, Acharya PA, Ahlen K: Central nervous system complications after 6000 retrobulbar blocks. Anesth Analg 66:1298–302, 1987 Patel BC, Burns TA, Crandall A: A comparison of topical and
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27. 28.
29. 30. 31. 32.
retrobulbar anesthesia for cataract surgery. Ophthalmology 103:1196–203, 1996 Petersen WC, Yanoff M, Danilenko AM: Complications of local ocular anesthesia. Int Ophthalmol Clin 32:23–30, 1992 Ripart J, Lefrant JY, de la Coussaye JE: Peribulbar versus retrobulbar anesthesia for ophthalmic surgery: an anatomical comparison of extraconal and intraconal injections. Anesthesiology 94:56–62, 2001 Rosen WJ: Brainstem anesthesia presenting as dysarthria. J Cataract Refract Surg 25:1170–1, 1999 Salama H, Farr AK, Guyton DL: Anesthetic myotoxicity as a cause of restrictive strabismus after scleral buckling surgery. Retina 20:478–82, 2000 Schacher S, Luthi M, Schipper I: [Vertical diplopia after cataract operation]. Klin Monatsbl Augenheilkd 216:295–7, 2000 Troll GF: Regional ophthalmic anesthesia: safe techniques and avoidance of complications. J Clin Anesth 7:163–72, 1995
The author has no commercial or proprietary interest in any product or idea discussed in this article. PII S0039-6257(01)00246-6
II. Topical/Intracameral Anesthesia for Cataract Surgery S. Akbar Hasan, MD,1 Henry F. Edelhauser, PhD,2 and Terry Kim, MD1 Departments of Ophthalmology, 1Duke University School of Medicine, Durham, North Carolina, and 2Emory University School of Medicine, Atlanta, Georgia, USA
The role of topical anesthesia in ophthalmic surgery has undergone prolific change in the last decade. In conjunction with the advent of advances in cataract surgery, topical anesthesia continues to gain increasing popularity. A survey of the practice styles and preferences of members of the American Society of Cataract and Refractive Surgery demonstrates a significant rise in the number of physicians using topical anesthesia. In 1995, approximately 8% of the respondents used topical anesthetics. In 1997, the number rose to 25%, and in 1999, 45% of the respondents employed topical agents for anesthesia. Its use was largely dependent on cataract surgery volume. Only 2% of physicians who performed five or fewer cases per month used topical anesthesia, whereas 73% of surgeons who performed more than 50 cases per month used topical anesthesia. Furthermore, 81% of the physicians performing cataract surgery with topical anesthesia also used intracameral lidocaine to supplement anesthesia.30 The use of topical anesthesia with cocaine for cataract extraction was first described in the United States by Knapp in 1884.27 Koller, working indepen-
dently, also reported the use of cocaine for ophthalmic surgery in the same year in Germany. Topical cocaine anesthesia, supplemented by subconjunctival anesthesia, remained the preferred method of pain control during cataract extraction until the 1930s, at which time retrobulbar and peribulbar regional blocks became the principal means of anesthesia.4,5,7, 11,36,38,41 The use of topical anesthesia in modern cataract surgery was reintroduced by Fichman in 1992.15 In 1995, Gills first reported the use of intracameral lidocaine in conjunction with topical anesthesia.18 Since its introduction, the use of intraocular lidocaine has also rapidly developed. Numerous subsequent studies have supported the use of topical and intracameral anesthesia with regards to efficacy and patient comfort. Advances in cataract surgery have provided an impetus for the recent interest and use of topical anesthesia. The development of sutureless, clear cornea, and small-incision cataract surgery with implantation of foldable intraocular lenses has significantly decreased operation times and tissue manipulation.8,33,39 Furthermore, improved instrumentation
VIEWPOINTS JONATHAN DUTTON AND THOMAS SLAMOVITS, EDITORS
Anesthesia for Intraocular Surgery I. Editorial: Anatomic Considerations in Ophthalmic Anesthesia. Jonathan J. Dutton, MD, PhD II. Topical/Intracameral Anesthesia for Cataract Surgery. S. Akbar Hasan, MD, Henry F. Edelhauser, PhD, and Terry Kim, MD III. Injectional Orbital Anesthesia for Cataract Surgery. Clark L. Springs, MD, and Geoffrey Broocker, MD Abstract. Surgeons must decide on the type of anesthesia to use when performing cataract surgery. These “Viewpoints” articles provide a well-balanced discussion offering the pros and cons of both topical anesthesia and retrobulbar/peribulbar injection. Dr. Dutton gives an overview of both techniques, focusing on the relevant orbital anatomy. Drs. Hasan, Edelhauser and Kim, review the various types of topical anesthesia currently in use, and Drs. Springs and Broocker examine retrobulbar and peribulbar injections. Both techniques are associated with advantages and risks, so each surgeon must decide which technique is best suited for his or her own practice. (Surv Ophthalmol 46:172–178, 2001. © 2001 by Elsevier Science Inc. All rights reserved.) Key words. anesthesia • cataract surgery • peribulbar injection • retrobulbar injection • topical anesthesia
I. Editorial: Anatomic Considerations in Ophthalmic Anesthesia Jonathan J. Dutton, MD, PhD Atlantic Eye & Face Center, Cary, North Carolina, and University of North Carolina, Chapel Hill, North Carolina, USA
Ophthalmic anesthesia has evolved over the decades into a sophisticated art. When properly applied it provides comfort to the patient, allays anxiety, and allows the safe execution of delicate eye surgery. While the retrobulbar block has been a standard for many decades, newer techniques, such as
the peribulbar and sub-Tenon’s blocks, and more recently topical anesthesia, have gained in popularity over the past several years. These less-invasive techniques have been promoted in order to reduce the risks of complications while still achieving adequate patient comfort.15,22,26 Regardless of the specific tech172
© 2001 by Elsevier Science Inc. All rights reserved.
0039-6257/01/$–see front matter
ANESTHESIA FOR INTRAOCULAR SURGERY
nique employed, knowledge of local and regional anatomy is essential in order to achieve the proper levels of sensory and motor blockade with minimal complications.32
Anatomic Complications of Retrobular Block For the retrobulbar and peribulbar blocks, a visual concept of orbital anatomy is critical to avoid injury to vascular and neural structures essential to visual function. Potential complications include globe perforation, optic nerve injury, subarachnoid injection, extraocular muscle injury, and orbital hemorrhage, among others. Globe perforation has been reported in as many as 0.75% of retrobulbar and peribulbar injections.6,8,10,24 Most commonly this involves a tangential penetration in the inferolateral quadrant, and may include penetration of the inferior oblique muscle as well. Retinal detachment and vitreous hemorrhage are common sequellae, with potential for visual loss. The risk of globe perforation is greater when a sharp-pointed, cutting-edge needle is used rather than a blunt retrobulbar needle, although globe perforation has been reported in both cases.12 Careful observation of the globe during needle entry may alert the surgeon or anesthetist to impending globe penetration by rotation of the eye toward the direction of needle entry. The so-called “wiggle test” is also useful in determining if the needle tip has impaled an orbital structure fixed to the eye. In this test, after the retrobulbar needle is in the orbit, but before any anesthetic is injected, the needle is moved from side to side; any rotation of the eye suggests that the sclera, optic nerve, or an extraocular muscle may have been penetrated. Injection of local anesthetic into the eye is a potentially devastating complication. The sclera is only 0.8- to 1.0-mm thick, and it offers little resistance to perforation by a sharp needle. Because the injection is into a closed space, the surgeon should be aware that resistance to fluid injection is elevated. As little as 40 mm Hg of pressure at the plunger head of the syringe can translate into more than 3000 mm Hg of intraocular pressure, enough to rupture the globe. Larger syringes have a greater mechanical advantage and therefore produce greater risk. Injection of anesthetic directly into the optic nerve can result in severe injury and immediate blindness. If the injection pressure is high, the operator should be aware of impending disaster. As mentioned above, if the “wiggle test” is positive, then the operator should withdraw the needle before injection. It is equally important to avoid penetration of the optic nerve sheath, and injection of anesthetic into the subarachnoid space. This compartment contains cerebrospinal fluid (CSF) in communication with
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the subdural intracranial and spinal CSF. Injection of anesthetic into this space may result in sensory blockade of contralateral vision, CNS depression, paralysis, seizures, hypotension, cardiac arrest, and even death.5,14,16,25,27,29 As with direct injection into the optic nerve, the “wiggle test” will be positive, but the increased injection pressure may not be immediately appreciated. Injury to an extraocular muscle may be more subtle, because there is very little resistance to needle penetration. The anterior ciliary arteries originate in the posterior orbit from the ophthalmic artery and penetrate the posterior one-third of the rectus muscles on their conal surface. These vessels run anteriorly and centrally within the muscle bellies and then on the outer surface of the muscle tendons to their points of insertion on the globe. These vessels then penetrate the sclera through emissary canals to supply the ciliary body, iris, and anterior choroidal circulation. The anterior ciliary vessels may be injured by the retrobulbar needle, resulting in retrobulbar orbital hemorrhage or hematoma directly into the muscle itself. The muscles most likely to be injured during needle entry are the inferior oblique or the inferior rectus muscles. While the inferior oblique does not contain ciliary vessels, it is a large and thick muscle that is highly vascular, and its location along the inferolateral globe back to the macula makes it particularly vulnerable to retrobulbar needle entry. Local anesthetics are quite toxic to striated muscle tissue. Inadvertent injection can result in muscle dysfunction ranging from mild and temporary paralysis to marked fibrosis.1 Postoperative muscle dysfunction may be seen even without any clinical evidence of muscle penetration and is the most frequent cause of postoperative strabismus following cataract or scleral buckle procedures.2,4,30,31 We have seen marked severe muscle fibrosis ensuing within days to weeks of such injury. In rare instances the strabismus may be neuropathic in origin due to injury to a cranial nerve near the orbital apex. Orbital hemorrhage is the most common complication of retrobulbar injection, reported in 0.1% to 1.7% of procedures.3,5,11 The orbit is highly vascular and contains numerous arteries and veins, as well as the ciliary vessels within the extraocular muscles. Most of the larger vessels are located in the superior and medial orbit, making these regions more vulnerable to vascular injury. The quadrant most devoid of larger vascular elements is inferolateral, and this is true of both the intraconal and extraconal compartments. Although very few vessels run in the peripheral orbital space, subperiosteal hemorrhage can occur from contact of the needle with the orbital bony walls, and in one case this resulted in blindness.9 While most orbital hemorrhagic events resolve un-
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eventfully, an acute bleed can loculate within the orbital septal fascial systems, producing a compartment syndrome. The resulting optic nerve and superior ophthalmic vein compression may cause visual loss or an excessive rise in intraocular pressure. Retrobulbar injection can also significantly reduce pulsatile ocular blood flow by about 250 l/min.13 This might have the potential to alter intraocular pressure, and it could compromise eyes with borderline blood flow. Hyaluronidase in the anesthetic agent has been reported to produce less reduction in blood flow.
Anatomic Complications of Sub-Tenon’s Block In the sub-Tenon’s block, Tenon’s capsule is elevated from the sclera, and local anesthetic is infused into the sub-Tenon’s/episcleral space. To be most effective, the anesthetic must diffuse back to the posterior globe near the optic nerve. Here the posterior ciliary nerves perforate Tenon’s capsule and pass through Tenon’s space to penetrate sclera (Fig. 1). These nerve branches originate from the ophthalmic division of the trigeminal nerve as the long posterior ciliary nerves, and as non-synapsing fibers passing through the ciliary ganglion, and run forward in the short posterior ciliary nerves. They carry sensory information from the ciliary body, iris, and cornea. In addition, the short posterior ciliary nerves carry post-synaptic parasympathetic motor fibers from the Edinger–Wesphal nucleus to the ciliary body and iris. Thus, placement of anesthetic into the posterior Tenon’s space will provide both sensory and motor blockade to the anterior intraocular structures, supplemented with topical anesthetic to the cornea and conjunctiva. The major potential complications of the subTenon’s block are injury to the sclera and to the cili-
Fig. 1. Sub-Tenon’s infusion with catheter placed beneath Tenon’s capsule. The anesthetic agent is injected and diffuses to the posterior ciliary nerves.
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ary nerves with the perfusing canula or catheter. Penetration of the globe has been reported, and nerve injury can result in pupillary or accommodative abnormalities. Orbital hemorrhage, although rare, has also been reported, presumably from penetration of posterior Tenon’s capsule.
Relevant Orbital Anatomy A detailed knowledge of orbital anatomy is not necessary for the delivery of safe anesthesia during ophthalmic surgery. Indeed, one only needs to have a visual picture of the major anatomic structures and their relationships during ocular movement. This visual, or “eidetic”, image allows the surgeon or anesthetist to navigate the orbit with greater confidence. From an anatomic perspective the orbit can be conceived as having three major compartments, the peripheral space, extraconal space, and intraconal space. The peripheral space is the potential space between periorbita and the orbital walls. It contains only a few vascular and neural elements penetrating bone to enter or leave the orbit. The intraconal space is defined as the conical compartment roughly bounded by the four rectus muscles, from the annulus of Zinn at the orbital apex to their penetration through Tenon’s capsule (Fig. 2). Although there is an extensive system of orbital fascial membranes interconnecting the muscles and suspending them to the orbital walls, nevertheless, the classic concept of an encircling membrane (the intermuscular septum) separating the extraconal from intraconal compartments is a conceptual convenience more than an anatomic reality.7,21 Anesthetic and other fluids can easily diffuse from the extraconal space into the intraconal compartment, which explains the equal efficacy of peribulbar and retrobulbar placement of anesthetic agents28 and the rapid distribution of hemorrhage throughout the orbit. The addition of hyaluronidase to the anesthetic agent may help diffusion across the interlobular septal membranes, thus enhancing the anesthetic effect and reducing the need for supplemental blocks.17 Within the orbit, larger vascular and neural elements are concentrated in the orbital apex, and they diverge as they extend forward. Thus, the greatest density of structures at greatest risk for injury is in the apical one-third of the orbit, approximately 30 to 45 mm behind the orbital rim. This is the region where the ciliary ganglion is located and where cranial nerves 3, 4, and 6 penetrate their respective extraocular muscles. The vortex veins, ophthalmic artery, superior and inferior ophthalmic veins, and the muscular arteries are also concentrated here. However, except for the inferior ophthalmic vein and its venous plexus, and the ciliary ganglion and nerves, most of these structures are situated in the superior
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175 Fig. 2. Major anatomical structures of the orbit. The intraconal space is defined as the compartment bounded by the four rectus muscles.
half of the orbit. Therefore, a needle inserted into the inferolateral intraconal space will present the lowest risk to these structures. Entry into the superior or superomedial orbit carries the highest risk of anatomic injury. In the posterior orbit, situated just inferior and lateral to the optic nerve, is the ciliary ganglion, where parasympathetic fibers destined for the ciliary body and iris synapse are present. This is the region of the orbit where the motor nerves to the extraocular muscles penetrate the conal surface of the muscles. This region, therefore, in the inferolateral posterior orbit is of major interest for retrobulbar
anesthesia because anesthetic placed here will block both sensory and motor innervation to the eye, as well as visual signals along the optic nerve. Such a block will generally not provide sensory block to the eyelids because these branches of the trigeminal nerve primarily run in the superior extraconal space and within the bony infraorbital canal in the floor. Thus, if eyelid surgery is contemplated, additional regional or local blocks must be given more anteriorly. Of great concern is the central retinal artery, located near the ciliary ganglion and entering the optic nerve on its inferior aspect. This is a relatively large structure in the central cone and has a great
Fig. 3. Shift in the position of orbital structures when the globe is in the upgaze position.
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DUTTON ET AL Fig. 4. Shift in the position of orbital structure when the globe is in the downgaze position.
deal of redundancy, coiling along the lateral side of the optic nerve. It therefore presents a significant target for potential injury. The length of the orbit is highly variable, as is the relative location of other anatomic structures. Ketsev et al20 measured the depth of the normal orbit and the position of the ciliary ganglion in cadaver specimens. They showed that the average distance from the inferolateral orbital rim to the apex is 48 mm, with a range of 42 to 54 mm. Similar findings were reported by Karampatakis et al.19 The annulus of Zinn, enclosing the optic nerve, extends 8–9 mm in front of the orbital apex; therefore, this immobile and more vulnerable portion of the nerve can lie as little as 33 mm from the orbital rim in the shortest orbits. Ketsev et al also showed that the average distance from the rim to the ciliary ganglion was 38 mm, with a range of 32–44 mm.20 Using a 40-mm retrobulbar needle, Karampatakis et al found that in
100% of cadaver specimens studied, the needle tip reached the posterior optic nerve, and in nearly 60% (7/12) it significantly pushed against the nerve.18 Even when a 35-mm needle is used, the tip engages the optic nerve sheath in 18% of cases. It is clear, therefore, that in order to ensure a safe approach to the orbital apex and ciliary ganglion, a retrobulbar needle should not exceed 31.5 mm in length.
Anatomy of Ocular Movement Of significant interest to the surgeon or anesthetist delivering retrobulbar anesthesia is the relative shift in position of the major anatomic structures with globe gaze positions. Knowledge of these relationships can allow us to manipulate these structures so as to maximize the safe zones for passage of the retrobulbar needle and to shift certain structures into less vulnerable positions.
Fig. 5. Position of orbital structures and the retrobulbar needle when the globe is in the primary gaze position.
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In the upgaze position, the optic nerve and ciliary ganglion are displaced downward into the inferior orbit, and the inferior oblique muscle is displaced forward toward the orbital rim (Fig. 3).This position lessens the risk of injury to the muscle, and makes it easier to achieve sensory blockade at the ciliary ganglion. However, it puts the optic nerve at greater risk of penetration. In the downgaze position, the optic nerve and ciliary ganglion are displaced upward, and the inferior oblique muscle is shifted backward (Fig. 4). This puts the muscle closer to the orbital floor behind the orbital rim and into the potential path of the retrobulbar needle. However, this is the safest position to prevent injury to the optic nerve. The primary gaze position offers a good compromise between optic nerve and inferior oblique muscle positions (Fig. 5). It also avoids having the patient look directly at the needle, and thus reduces potential apprehension. In this position the retrobulbar needle can be introduced at the inferolateral orbital rim and advanced parallel to the floor to the level of the posterior globe. It must be kept in mind that the posterior globe position depends on many factors and can be highly variable among patients. The relative degree of proptosis or shallowness of the orbit can significantly alter the depth of the globe within the orbit, as can the degree of myopia and globe size.23 The posterior sclera can vary from less than 10 mm behind the orbital rim to more than 18 mm. In patients with orbital diseases, such as Graves’ disease, or in those with marked enophthalmos from trauma, this disparity can be even greater. A careful evaluation of the globe in relation to the orbital rims will help determine the probable depth of the posterior pole. When the advancing retrobulbar needle reaches the posterior surface of the globe, the needle must be directed slightly upward. At this point the bony orbital floor slopes upward to the apex at an angle of about 10 to 15 degrees. In the traditional retrobulbar injection, the needle tip is advanced into the intraconal space between the lateral and inferior rectus muscles to reach the vicinity of the ciliary ganglion. As mentioned above, this region of the orbit is relatively empty of vascular structures and therefore provides relative safety. In the peribulbar block, the anesthetic is injected within the extraconal space without penetrating the muscle cone.
Conclusion It should be clear that the placement of a needle and injection of anesthesia into the orbit is not a procedure to be taken lightly or to be casually performed by the novice. Although the vast majority of
procedures proceed uneventfully, the risks are significant and the potential complications can be devastating. Techniques that minimize these risks are available, both as modifications to the classic retrobulbar block or as one of the newer, less invasive techniques. In the articles that follow this one, a balanced discussion is presented for both retrobulbar injection and topical anesthesia in cataract surgery. In the first discussion, Drs. Hasan, Edelhauser, and Kim review the various types of topical anesthesia currently in use, and they present the in vivo data supporting the use of adjuvant intracameral anesthesia. Drs. Springs and Broocker focus on retrobulbar and peribulbar injections as effective alternatives in cataract surgery. Both approaches are associated with distinct advantages and potential risks, and every surgeon must evaluate for himself or herself the benefits of each technique in their own practice.
References 1. Ando K, Oohira A, Takao M: Restrictive strabismus after retrobulbar anesthesia. Jpn J Ophthalmol 41:23–6, 1997 2. Brown SM, Brooks SE, Mazow ML: Cluster of diplopia cases after periocular anesthesia without hyaluronidase. J Cataract Refract Surg 25:1245–9, 1999 3. Cionni RJ, Osher RH: Retrobulbar hemorrhage. Ophthalmology 98:1153–5, 1991 4. Corboy JM, Jiang X: Postanesthetic hypotropia: a unique syndrome in left eyes. J Cataract Refract Surg 23:1394–8, 1997 5. Davis DB 2nd, Mandel MR: Efficacy and complication rate of 16,224 consecutive peribulbar blocks. A prospective multicenter study. J Cataract Refract Surg 20:327–37, 1994 6. Duker JS, Belmont JB, Benson WE: Inadvertent globe perforation during retrobulbar and peribulbar anesthesia. Patient characteristics, surgical management, and visual outcome. Ophthalmology 98:519–26, 1991 7. Dutton JJ: Clinical and Surgical Orbital Anatomy. Philadelphia, W.B. Saunders Company, 1994, pp 93–111 8. Edge R, Navon S: Scleral perforation during retrobulbar and peribulbar anesthesia: risk factors and outcome in 50,000 consecutive injections. J Cataract Refract Surg 25:1237–44, 1999 9. Girard LJ: Subperiosteal orbital hemorrhage from retrobulbar injection resulting in blindness. Arch Ophthalmol 115: 1085–6, 1997 10. Grizzard WS, Kirk NM, Pavan PR: Perforating ocular injuries caused by anesthesia personnel. Ophthalmology 98:1011–6, 1991 11. Hamilton RC, Gimbel HV, Strunin L: Regional anaesthesia for 12,000 cataract extraction and intraocular lens implantation procedures. Can J Anaesth 35:615–23, 1988 12. Hay A, Flynn HW Jr, Hoffman JI, Rivera AH: Needle penetration of the globe during retrobulbar and peribulbar injections. Ophthalmology 98:1017–24, 1991 13. Hulbert MF, Yang YC, Pennefather PM, Moore JK: Pulsatile ocular blood flow and intraocular pressure during retrobulbar injection of lignocaine: influence of additives. J Glaucoma 7:413–6, 1998 14. Jackson K, Vote D: Multiple cranial nerve palsies complicating retrobulbar eye block. Anaesth Intensive Care 26:662–4, 1998 15. Jacobi PC, Dietlein TS, Jacobi FK: A comparative study of topical vs retrobulbar anesthesia in complicated cataract surgery. Arch Ophthalmol 118:1037–43, 2000 16. Javitt JC, Addiego R, Friedberg HL: Brain stem anesthesia after retrobulbar block. Ophthalmology 94:718–24, 1987 17. Kallio H, Paloheimo M, Maunuksela EL: Hyaluronidase as
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Surv Ophthalmol 46 (2) September–October 2001 an adjuvant in bupivacaine-lidocaine mixture for retrobulbar/peribulbar block. Anesth Analg 91:934–7, 2000 Karampatakis V, Natsis K, Gigis P, Stangos NT: The risk of optic nerve injury in retrobulbar anesthesia: a comparative study of 35 and 40 mm retrobulbar needles in 12 cadavers. Eur J Ophthalmol 8:184–7, 1998 Karampatakis V, Natsis K, Gigis P, Stangos NT: Orbital depth measurements of human skulls in relation to retrobulbar anesthesia. Eur J Ophthalmol 8:118–20, 1998 Katsev DA, Drews RC, Rose BT: An anatomic study of retrobulbar needle path length. Ophthalmology 96:1221–4, 1989 Koornneef L: The architecture of the musculo-fibrous apparatus in the human orbit. Acta Morphol Neerl Scand 15:35– 64, 1977 Leaming DV: Practice styles and preferences of ASCRS members—1998 survey. J Cataract Refract Surg 25:851–9, 1999 Modarres M, Parvaresh MM, Hashemi M, Peyman GA: Inadvertent globe perforation during retrobulbar injection in high myopes. Int Ophthalmol 21:179–85, 1997 Mount AM, Seward HC: Scleral perforations during peribulbar anaesthesia. Eye 7:766–7, 1993 Nicoll JM, Acharya PA, Ahlen K: Central nervous system complications after 6000 retrobulbar blocks. Anesth Analg 66:1298–302, 1987 Patel BC, Burns TA, Crandall A: A comparison of topical and
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retrobulbar anesthesia for cataract surgery. Ophthalmology 103:1196–203, 1996 Petersen WC, Yanoff M, Danilenko AM: Complications of local ocular anesthesia. Int Ophthalmol Clin 32:23–30, 1992 Ripart J, Lefrant JY, de la Coussaye JE: Peribulbar versus retrobulbar anesthesia for ophthalmic surgery: an anatomical comparison of extraconal and intraconal injections. Anesthesiology 94:56–62, 2001 Rosen WJ: Brainstem anesthesia presenting as dysarthria. J Cataract Refract Surg 25:1170–1, 1999 Salama H, Farr AK, Guyton DL: Anesthetic myotoxicity as a cause of restrictive strabismus after scleral buckling surgery. Retina 20:478–82, 2000 Schacher S, Luthi M, Schipper I: [Vertical diplopia after cataract operation]. Klin Monatsbl Augenheilkd 216:295–7, 2000 Troll GF: Regional ophthalmic anesthesia: safe techniques and avoidance of complications. J Clin Anesth 7:163–72, 1995
The author has no commercial or proprietary interest in any product or idea discussed in this article. PII S0039-6257(01)00246-6
II. Topical/Intracameral Anesthesia for Cataract Surgery S. Akbar Hasan, MD,1 Henry F. Edelhauser, PhD,2 and Terry Kim, MD1 Departments of Ophthalmology, 1Duke University School of Medicine, Durham, North Carolina, and 2Emory University School of Medicine, Atlanta, Georgia, USA
The role of topical anesthesia in ophthalmic surgery has undergone prolific change in the last decade. In conjunction with the advent of advances in cataract surgery, topical anesthesia continues to gain increasing popularity. A survey of the practice styles and preferences of members of the American Society of Cataract and Refractive Surgery demonstrates a significant rise in the number of physicians using topical anesthesia. In 1995, approximately 8% of the respondents used topical anesthetics. In 1997, the number rose to 25%, and in 1999, 45% of the respondents employed topical agents for anesthesia. Its use was largely dependent on cataract surgery volume. Only 2% of physicians who performed five or fewer cases per month used topical anesthesia, whereas 73% of surgeons who performed more than 50 cases per month used topical anesthesia. Furthermore, 81% of the physicians performing cataract surgery with topical anesthesia also used intracameral lidocaine to supplement anesthesia.30 The use of topical anesthesia with cocaine for cataract extraction was first described in the United States by Knapp in 1884.27 Koller, working indepen-
dently, also reported the use of cocaine for ophthalmic surgery in the same year in Germany. Topical cocaine anesthesia, supplemented by subconjunctival anesthesia, remained the preferred method of pain control during cataract extraction until the 1930s, at which time retrobulbar and peribulbar regional blocks became the principal means of anesthesia.4,5,7, 11,36,38,41 The use of topical anesthesia in modern cataract surgery was reintroduced by Fichman in 1992.15 In 1995, Gills first reported the use of intracameral lidocaine in conjunction with topical anesthesia.18 Since its introduction, the use of intraocular lidocaine has also rapidly developed. Numerous subsequent studies have supported the use of topical and intracameral anesthesia with regards to efficacy and patient comfort. Advances in cataract surgery have provided an impetus for the recent interest and use of topical anesthesia. The development of sutureless, clear cornea, and small-incision cataract surgery with implantation of foldable intraocular lenses has significantly decreased operation times and tissue manipulation.8,33,39 Furthermore, improved instrumentation