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A randomized clinical trial of combined topical-intracameral anesthesia in cataract surgery1
A Randomized Clinical Trial of Combined Topical–Intracameral Anesthesia in Cataract Surgery Sung-Huei Tseng, MD, Fred Kuanfu Chen Objective: To evaluate the level of patient discomfort during phacoemulsification and implantation of a foldable intraocular lens (IOL) while under topical lidocaine, alone or in combination with intracameral lidocaine. Design: A prospective, randomized, controlled trial. Participants: Between January and July 1997, a total of 162 patients (162 eyes) scheduled for cataract surgery were randomly assigned to either the placebo group (topical anesthesia with intracameral balanced salt solution [group 1, n ⫽ 81]) or the interventional group (combined topical–intracameral anesthesia [group 2, n ⫽ 81]). Interventions: All patients underwent temporal clear corneal phacoemulsification and implantation of a foldable silicone IOL. All patients received a minimum total of five doses (two drops per dose) of 2% topical lidocaine hydrochloride. Three doses were administered before surgery into the superior and inferior cul-de-sac at 10 minutes, 5 minutes, and immediately before the initial corneal incision. One dose was administered before the commencement of phacoemulsification and another dose before implantation of the IOL. In addition, all patients received an intracameral injection immediately after entrance into the anterior chamber. Patients in group 1 received a 0.5-ml injection of balanced salt solution, and those in group 2 received a 0.5-ml injection of 1% lidocaine. Main Outcome Measure: A 10-point visual analogue scale was used immediately after the surgery to assess each patient’s overall severity of pain intraoperatively. Results: Ninety percent of patients in group 1 and 95% in group 2 assigned a score of 0 or 1 to the level of intraoperative discomfort. The mean pain score ⫹/⫺1 standard deviation for group 1 was 0.63 ⫾ 0.68 and for group 2 was 0.37 ⫾ 0.58. The difference between the pain scores for the two groups was statistically significant (P ⫽ 0.0053). A small but significant proportion (15%) of patients in group 1 expressed distress when the ciliary body was stretched or the iris was manipulated with instruments. Conclusion: Although topical lidocaine alone provides adequate anesthesia for phacoemulsification and implantation of a foldable IOL, combined topical and intracameral administration of lidocaine can further minimize intraoperative discomfort. Ophthalmology 1998;105:2007–2011 Retrobulbar injection of an anesthetic agent, which has been used for more than a century for cataract surgery, is associated with a number of potentially sight- or even life-threatening complications.1–10 Alternative anesthetic procedures have been developed to reduce the risks of injuring intraorbital structures, but none are completely devoid of complications.11–17 Advances in cataract surgery, including the use of a smaller, self-sealing incision and intracapsular phacoemulsification with implantation of a foldable intraocular lens (IOL), have shortened the duration of operation such that the use of shorter-
Originally received: December 15, 1997. Revision accepted: June 1, 1998. Manuscript no. 97853. From the Department of Ophthalmology, College of Medicine, National Cheng Kung University, Tainan, Taiwan, Republic of China. The authors have no proprietary interest in the development or marketing of any device or medications mentioned in the article or any competing device. Address correspondence and reprint requests to Sung-Huei Tseng, MD, C-6-1 No. 61 Shaw Dong Road, Tainan, Taiwan, R.O.C.
acting anesthetic agents and less-invasive methods of its administration can now be used. Topical anesthesia alone for cataract removal and IOL implantation was first proposed by Fichman (Fichman RA, MD. Phacoemulsification with Posterior Chamber IOL Can Be Performed with Use of Topical Anesthesia. Presented at the Symposium on Cataract, IOL and Refractive Surgery, San Diego, April 1992). This anesthetic technique has been increasingly accepted as the number of surgeons performing clear corneal phacoemulsification increases.18 –25 Unlike injection of anesthetic agents, topical administration of anesthetic agents is associated with minimal discomfort. The risk of ptosis and bruising is nonexistent and that of injuring ocular tissues or causing life-threatening systemic side effects is minimal. It also has the advantage over other methods in that the vision is restored instantly after the operation and undesirable cosmetic side effects are altogether avoided. In addition to all of these advantages, the technique is economical. However, with topical anesthesia, the agent blocks only trigeminal nerve endings in the cornea and the conjunctiva,
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Ophthalmology Volume 105, Number 11, November 1998 leaving the intraocular structures in the anterior segment unanesthetized. Thus, manipulation of the iris or stretching of the ciliary and zonular tissues, which is inevitable during the surgery, could irritate the unanesthetized ciliary nerves and result in discomfort. This forced Fukasaku and Marron26 to abandon topical anesthesia in favor of peribulbar injection. More recently, increasing numbers of ophthalmologists administer anesthetic agents by intracameral injection or by adding an anesthetic agent to the irrigation fluid used during the intraocular phase of surgery.27,28 To investigate the efficacy of intracameral anesthesia, we designed a prospective, randomized, controlled trial comparing topically administered lidocaine with intracameral injection of balanced salt solution (BSS) or lidocaine in patients undergoing phacoemulsification and implantation of a foldable IOL.
Patients and Methods From January to July 1997, a total of 162 patients were eligible for phacoemulsification surgery and implantation of an IOL with topical anesthesia and gave written, informed consent to participate in the study. Patients were excluded from the study if they had a history of hearing impairment, dementia, movement disorder, or excessive anxiety; had poor fixation due to nystagmus, strabismus, or cataract; or were not native speakers of the language used in the documentation of informed consent. Other contraindications to participation in this study included known allergic response to lidocaine or other topical anesthetic agents and corneal or ocular conditions precluding the use of topical anesthesia. A random numbers table was used to assign each patient entering the study to either group 1 (n ⫽ 81) or group 2 (n ⫽ 81). All patients in both groups received a minimum total of five doses of topical anesthesia for phacoemulsification and implantation of a 6.0-mm-diameter foldable silicone IOL (AMO Model SI-30NB; Allergan, Irvine, CA). In addition, all patients received an intracameral injection immediately after entrance into the anterior chamber, but only patients in group 2 received an injection that contained the active anesthetic agent.
study. First, a corneal groove of 300 m in depth and 3.2 mm in length was fashioned at the temporal limbus. Then, a 1.5- to 2-mm-long corneal tunnel was made with a crescent knife (No. 1118; Visitec, Sarasota, FL). Finally, after creation of a sideport incision at the 2-o’clock position to the left of the main incision, a slit knife (Surgical Specialties Co. REF 72-2561; Reading, PA) was used to penetrate Descemet membrane, with a downward pressure at the tip of the knife, resulting in a 2.5-mm internal valve. For patients in group 2, 0.5 ml of 1% preservative-free lidocaine (an equal-volume mixture of 2% lidocaine and BSS) was injected slowly through the incision into the anterior chamber. For patients in group 1, who served as control subjects, the same technique was used to inject 0.5 ml of BSS as a placebo. The anterior chamber was then filled with a viscoelastic substance (Viscoat; Alcon, Humacao, Puerto Rico). A continuous curvilinear capsulorhexis was performed with capsule forceps while the eyeball was immobilized with a 0.12-mm forceps. This was followed by hydrodissection, hydrodelineation, phacoemulsification with the divide-and-conquer technique, and then instrumental removal of residual lens cortex. The length of the incision then was extended to 3.2 mm to permit insertion of a 6.0-mm foldable IOL. Shortly after positioning of the IOL, carbachol 0.01% (Miostat; Alcon Surgical, Ft. Worth, TX) was injected to constrict the pupil. The viscoelastic substance was aspirated, and BSS was injected at the entrance of the corneal tunnels for hydration of the stroma. The wound was tested for leakage of fluid by gentle compression with a Merocel sponge, and none of the patients required a suture to close the wound. Finally, one drop of 5% povidone–iodine solution was instilled into the conjunctival sac before the lid speculum was removed.
Patient Evaluations of Pain At the completion of the operation, each patient was shown a visual analogue pain scale with numeric and descriptive ratings from 0 (“no pain”) to 10 (“maximum pain”), as described by Stevens.29 Patients were asked to use this 10-point scale to rate the level of pain felt during the operation, including pain felt after delivery of topical and intracameral agents. If patients were unable to read the printed numbers and descriptive text on the pain scale, the examiner read them to the patient. In addition, we recorded any verbal expression of pain that patient made during the operation (e.g., with manipulation of the iris).
Technique of Topical Anesthesia Patients were given oral fludiazepam (Erispan; Sumitomo Pharmaceutical, Osaka, Japan), 0.5 mg, and acetaminophen, 1.0 g, 1 hour before surgery. Ten minutes before the surgery, two drops of unpreserved, methylparaben-free lidocaine 2% (Xylocaine; Fujisawa Pharmaceutical, Osaka, Japan) were instilled into the superior and inferior cul-de-sacs. This was followed by additional two-drop doses into the cul-de-sacs at 5 minutes and immediately before the start of surgery. Intraoperatively, two-drop doses of lidocaine were administered onto the ocular surface immediately before commencement of phacoemulsification and before implantation of the IOL. Additional doses were given if the patient gave indication of discomfort during the procedure or when the procedure was prolonged.
Surgical Procedure and Intracameral Anesthesia All surgical procedures were performed by one surgeon (SHT). Temporal clear corneal incision was made using a “three-plane” technique while the eyeball was immobilized with a Thorton–Fine ring. Rectus bridle sutures were not used in the operations in this
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Statistical Analysis Student’s t test for two samples was used to compare characteristics of the two study groups. To evaluate differences between the pain scores of the two groups, the Mann–Whitney U test was used because the data were not normally distributed. Statistical analyses were performed using the StatView statistical package (Abacus Concepts Inc, Berkeley, CA). The null hypothesis was rejected if the P value was less than 0.05.
Results The average age of all patients in the study was 67.2 ⫾ 7.9 years (range, 43– 84 years) and approximately 60% were female (Table 1). Differences between the two study groups in age and gender distribution were not statistically significant (P ⫽ 0.13). None of the patients in the study experienced complications due to the method of anesthetic administration or drug toxicity that were severe enough to interfere with continuation of the operation.
Tseng and Chen 䡠 Intracameral Anesthesia for Cataract Surgery Table 1. Characteristics of 162 Patients Randomly Assigned to Receive Topical Lidocaine with or without Intracameral Lidocaine for Phacoemulsification and Intraocular Lens Implantation
Characteristic Age (yrs) (mean ⫾ SD) Range Female (%) Pain score (scale of 0–10) Mean Range
Group 1: Group 2: Intracameral BBS Intracameral Lidocaine (n ⴝ 81) (n ⴝ 81) 66.1 ⫾ 7.7 46–83 59.3 0.63 ⫾ 0.68 0–3
67.8 ⫾ 7.9 43–84 62.3 0.37 ⫾ 0.58 0–4
BSS ⫽ balanced salt solution; SD ⫽ standard deviation.
No one in either study group reported discomfort beyond mild stinging with topical administration of anesthetic, and none experienced operative discomfort sufficient to warrant supplemental peribulbar anesthesia or intravenous sedation. All patients expressed satisfaction with the anesthesia for their surgery. In eyes with small pupils (two eyes in group 1 and three eyes in group 2) due to diabetes or prolonged use of miotics, sphincterotomy and pupiloplasty were performed to facilitate phacoemulsification. Furthermore, in one patient from group 2, the surgery was complicated by a small posterior capsule rupture and loss of vitreous intraoperatively. However, this patient was able to tolerate a mechanical, anterior vitrectomy without supplemental retrobulbar or peribulbar anesthesia. Finally, a foldable IOL was implanted into the capsular bag in this eye without difficulty. Because topical and intracameral instillation of anesthetic drugs cannot achieve akinesia, some patients exhibited a strong blink–Bell’s phenomenon during the operation. When this occurred, the “psycholinguistics” technique described by Fichman24 was used and environmental light intensity and other stimuli were decreased to calm the patient and improve his or her ability to concentrate on the microscope light. The pain scores reported by patients after surgery are shown in Figure 1. Seventy-three patients in group 1 (90%) and 77 patients in group 2 (95%) reported no pain (a score of 0) or only minimal discomfort (a score of 1), and none of the patients reported a pain score of 5 or above (Fig 1). The mean pain score in group 1 (control subjects) was 0.63 ⫾ 0.68, and in group 2, it was 0.37 ⫾ 0.58. The difference between the mean pain scores for the two groups was statistically significant (P ⫽ 0.0053). During surgery, approximately 15% of patients in group 1 verbalized discomfort, usually with manipulation of the iris, sudden distention of the anterior chamber by irrigating fluid after introduction of the phacoemulsification tip, or hydrodissection or rotation of the nucleus. Some patients even verbalized discomfort on administration of Miostat. The most severe pain expressed was during the use of a spatula to reposition a prolapsed iris. A smaller proportion of patients in group 2 (2.5%) reported ocular discomfort during such manipulations, although most described a sensation of “abrupt ocular soreness” when lidocaine was injected intracamerally. Such discomfort generally lasted for only a few seconds.
Discussion Since 1993, when Kershner first reported the advantages of topical anesthesia in scleral pocket phacoemulsification,18 a
number of reports favoring this methodology have appeared.19 –25 In one study, in which topical anesthesia was used in one eye and retrobulbar injection in the other eye of the same patient, 61.5% of patients selected topical over retrobulbar injection as the preferred method of anesthetic administration.25 However, in the 1995 annual survey of the American Society of Cataract and Refractive Surgery, only 8% of responding members indicated a preference for topical anesthesia over posterior orbital injections for patients undergoing cataract surgery, which was only a slight increase from 4% in 1993 and nearly 0% in 1992.30,31 In addition, when Fukasaku and Marron26 compared topical with retrobulbar anesthesia, they found more intraoperative pain with the topical approach. The problem may be related to the limited ability of topical anesthetic agents to penetrate the ocular tissues. To achieve analgesia during intraocular surgery, impulses in pain fibers exiting the eye must be blocked completely, including impulses in the long sensory fibers from the cornea, the iris, and the ciliary body to the ciliary ganglion. Failure of topical anesthesia to block sensations in all these fibers makes intraoperative manipulation of the iris particularly uncomfortable for patients undergoing intraocular procedures with topical anesthesia only. Various techniques have been advocated to alleviate patient discomfort associated with intraocular manipulation. Grabow20 emphasized the importance of adequate cycloplegia to minimize stretching of zonules and the ciliary muscle, and Novak and Koch23 recommended lowering of the irrigating solution bottle to minimize the hydrostatic pressure that could cause pain by stretching the ciliary body. Early in the development of techniques for topical anesthesia for phacoemulsification, intravenous sedation was often used as an adjunct.18,20 –23,25,32 None of the patients in our series required this intervention, and the mean pain scores of 0.63 and 0.37 for patients in group 1 and group 2, respectively, were similar to the mean pain score of 0.41 reported by Patel and associates25 for patients in their study. We believe that the low level of discomfort in our patients, even in the placebo group, may be explained by the speed with which we performed phacoemulsification and the caution we exercised during intraocular manipulation.
Figure 1. Number of patients reporting pain scores of 0 (‘‘no pain’’) to 10 (‘‘worst pain’’) during phacoemulsification and implantation of a foldable intraocular lens. Black bars ⫽ topical anesthesia only; white bars ⫽ combined topical and intracameral anesthesia.
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Ophthalmology Volume 105, Number 11, November 1998 Intracameral Instillation of Anesthetic Agent Although the majority of patients in both groups in our study experienced no or only minimal discomfort intraoperatively, the difference in mean pain scores for the two groups was statistically significant. The efficacy of intracameral block was particularly striking when intraocular manipulation was required. Patients who received only topical anesthesia were more likely to experience discomfort during iris manipulation, zonular stretching, and spasm of the ciliary body induced by injection of Miostat. In contrast, patients who received intracameral anesthesia as well as topical lidocaine were practically oblivious to such manipulations. One would expect the pain to be particularly intense with the group 2 patient who required immediate anterior vitrectomy for rupture of the posterior capsule. However, he was able to tolerate the procedure and later rated the pain as only mild to moderate (a score of 4), although he was anesthetized only with topical and intracameral instillation of lidocaine. Our observations seemed to agree with those of Gills et al27 and Koch,28 who recently reported that irrigation of the anterior chamber with unpreserved lidocaine alleviated the intraocular discomfort of some patients undergoing cataract extraction and implantation of an IOL while under topical anesthesia. We also noticed that intracameral anesthesia was particularly effective in reducing patient discomfort when synechiolysis or sphincterotomy was required or iris retractors were used to enlarge the pupil.
Adverse Effects of Intracameral Injection of Lidocaine Despite the efficacy of supplementary intracameral lidocaine, nearly all patients in group 2 experienced abrupt and very transient ocular discomfort immediately after the injection into the anterior chamber. This sensation may result from the direct irritation of the tissues caused by the lidocaine. A word of warning was sufficient to ward off the patient’s anxiety.
Contraindications to Intracameral Injection of Lidocaine Contraindications to the combined approach are similar to contraindications to topical administration of anesthesia alone. For example, the combined approach is not suitable for patients with a high degree of anxiety, those with hearing difficulties or mental retardation, or patients with an opaque cataract, as they cannot fixate on the operating microscope light.
Toxic Effects of Intracameral Lidocaine There is a concern that intracameral injection of an anesthetic agent may cause intraocular injury, particularly to the corneal endothelium and the retina. Toxic effects of the commonly available topical anesthetic agents on the corneal epithelium have been studied extensively,33 but little is known of their toxic effects on corneal endothelium. A
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report of several cases in which inadvertent injection of lidocaine into the anterior chamber had no ill effects supported the hypothesis that routine intraocular injection of this local anesthetic may be safe and effective as part of the anesthesia regimen.34 In contrast, a recent study in a rabbit model35 found that injections of unpreserved lidocaine hydrochloric acid 4% into the anterior chamber for days produced significant corneal thickening and opacification, from which the authors concluded that topical anesthetic agents should not be allowed to reflux into the anterior chamber. However, in the same study, injection of a diluted (1:10) solution of unpreserved lidocaine failed to produce any significant increase in corneal thickness or opacification in the rabbits. Furthermore, Kim et al36 evaluated the direct effect of preservativefree lidocaine hydrochloric acid 1% on the corneal endothelium using an in vitro perfusion system, and their results showed that lidocaine hydrochloric acid 1% only caused the endothelium of human and rabbit corneas a transient edema. In the clinical setting in which lidocaine was intracamerally injected, the amount of the anesthetic agent and the time it was in contact with corneal endothelium before being flushed from the eye were negligible compared to a study conducted on rabbits. We consider that such brief exposure to lidocaine is unlikely to injure the corneal endothelium. Of note, however, is the finding of another study in rabbits that the preservatives, such as benzalkonium chloride at a concentration of 0.025% to 0.05% in commercially available anesthetic agents, may cause irreversible damages to the corneal tissues.37 Only unpreserved lidocaine should be used for intracameral injection. In support of our conclusion, Gills et al27 also found no evidence of significant endothelial cell loss or injury in patients who received intracameral injections of unpreserved lidocaine. Our slit-lamp biomicroscopic examination showed no evidence of corneal pathology, edema, thickening, or other toxicity, nor did any patients in our study have unexplained iritis or other unusual intraocular inflammation develop. Even in a study in which transient visual loss occurred in a patient receiving intracameral injections of lidocaine, vision recovered completely within hours with no untoward effects.38 The transient visual loss in this case probably was caused by effects of the topical anesthetic agent on the retinal nerve fiber layer, in turn because of lack of the barrier effect of posterior capsule, zonules, and vitreous humor. Incidentally, therefore, the retina must be resistant to toxic effects of low concentrations of intracameral unpreserved lidocaine. Thus, currently, unpreserved intracameral lidocaine seems to be safe for the cornea, the anterior chamber, and the retina, although a larger series of evaluations is called for before a definite conclusion can be drawn. In conclusion, combining topical and intracameral anesthesia for cataract surgery offers significant benefits over topical anesthesia alone in terms of patient comfort. We believe that the combined topical–intracameral approach will probably become the standard ophthalmic anesthetic technique in phacoemulsification.
Tseng and Chen 䡠 Intracameral Anesthesia for Cataract Surgery
References 1. Duker JS, Belmont JB, Benson WE, et al. Inadvertent globe perforation during retrobulbar and peribulbar anesthesia. Patient characteristics, surgical management, and visual outcome. Ophthalmology 1991;98:519 –26. 2. Sullivan KL, Brown GC, Forman AR, et al. Retrobulbar anesthesia and retinal vascular obstruction. Ophthalmology 1983;90:373–7. 3. Feibel RM. Current concepts in retrobulbar anesthesia. Surv Ophthalmol 1985;30:102–10. 4. Hay A, Flynn HW Jr, Hoffman JI, Rivera AH. Needle penetration of the globe during retrobulbar and peribulbar injections. Ophthalmology 1991;98:1017–24. 5. Morgan CM, Schatz H, Vine AK, et al. Ocular complications associated with retrobulbar injections. Ophthalmology 1988; 95:660 –5. 6. Smith JL. Retrobulbar bupivacaine can cause respiratory arrest. Ann Ophthalmol 1982;14:1005– 6. 7. Meyers EF. Brain-stem anesthesia after retrobulbar block [letter]. Arch Ophthalmol 1985;103:1278,1282. 8. Javitt JC, Addiego R, Friedberg HL, et al. Brain stem anesthesia after retrobulbar block. Ophthalmology 1987;94:718 – 24. 9. Hamilton RC. Brain stem anesthesia following retrobulbar blockade. Anesthesiology 1985;63:688 –90. 10. Nicoll JMV, Acharya PA, Ahlen K, et al. Central nervous system complications after 6000 retrobulbar blocks. Anesth Analg 1987;66:1298 –302. 11. Arnold PN. Prospective study of a single-injection peribulbar technique. J Cataract Refract Surg 1992;18:157– 61. 12. Whitsett JC, Balyeat HD, McClure B. Comparison of oneinjection-site peribulbar anesthesia and retrobulbar anesthesia. J Cataract Refract Surg 1990;16:243–5. 13. Bloomberg LB. Administration of periocular anaesthesia. J Cataract Refract Surg 1986;12:677–9. 14. Bloomberg LB. Anterior periocular anesthesia: five years experience. J Cataract Refract Surg 1991;17:508 –11. 15. Kimble JA, Morris RE, Witherspoon CD, Feist RM. Globe perforation from peribulbar injection [letter]. Arch Ophthalmol 1987;105:749. 16. Smith R. Cataract extraction without retrobulbar anaesthetic injection. Br J Ophthalmol 1990;74:205–7. 17. Hansen EA, Mein CE, Mazzoli R. Ocular anesthesia for cataract surgery: a direct sub-Tenon’s approach. Ophthalmic Surg 1990;21:696 –9. 18. Kershner RM. Topical anesthesia for small incision self-sealing cataract surgery. A prospective evaluation of the first 100 patients. J Cataract Refract Surg 1993;19:290 –2. 19. Shuler JD. Topical anesthesia in a patient with a history of retrobulbar hemorrhage. Arch Ophthalmol 1993;111:733.
20. Grabow HB. Topical anaesthesia for cataract surgery. Eur J Implant Refract Surg 1993;5:20 – 4. 21. Bloomberg LB, Pellican KJ. Topical anesthesia using the Bloomberg SuperNumb Anesthetic Ring. J Cataract Refract Surg 1995;21:16 –20. 22. Dinsmore SC. Drop, then decide approach to topical anesthesia. J Cataract Refract Surg 1995;21:666 –71. 23. Novak KD, Koch DD. Topical anesthesia for phacoemulsification: initial 20-case series with one month follow-up. J Cataract Refract Surg 1995;21:672–5. 24. Fichman RA. Use of topical anesthesia alone in cataract surgery. J Cataract Refract Surg 1996;22:612– 4. 25. Patel BCK, Burns TA, Crandall A, et al. A comparison of topical and retrobulbar anesthesia for cataract surgery. Ophthalmology 1996;103:1196 –203. 26. Fukasaku H, Marron JA. Pinpoint anesthesia: a new approach to local ocular anesthesia. J Cataract Refract Surg 1994;20: 468 –71. 27. Gills JP, Cherchio M, Raanan MG. Unpreserved lidocaine to control discomfort during cataract surgery using topical anesthesia. J Cataract Refract Surg 1997;23:545–50. 28. Koch PS. Anterior chamber irrigation with unpreserved lidocaine 1% for anesthesia during cataract surgery. J Cataract Refract Surg 1997;23:551– 4. 29. Stevens JD. A new local anaesthesia technique for cataract extraction by one quadrant sub-Tenon’s infiltration. Br J Ophthalmol 1992;76:670 – 4. 30. Leaming DV. Practice styles and preferences of ASCRS members—1995 survey. J Cataract Refract Surg 1996;22:931–9. 31. Leaming DV. Practice styles and preferences of ASCRS members—1993 survey. J Cataract Refract Surg 1994;20:459 – 67. 32. Dinsmore SC. Approaching a 100% success rate using topical anesthesia with mild intravenous sedation in phacoemulsification procedure. Ophthalmic Surg Lasers 1996;27:935– 8. 33. Rosenwasser GOD. Complications of topical ocular anesthetics. Int Ophthalmol Clin 1989;29:153– 8. 34. Gills JP, Hustead RF, Sanders DR, eds. Ophthalmic Anesthesia. Thorofare, NJ: SLACK Inc, 1993:187–202. 35. Judge AJ, Najafi K, Lee DA, Miller KM. Corneal endothelial toxicity of topical anesthesia. Ophthalmology 1997;104: 1373–9. 36. Kim T, Holley GP, Lee JH, et al. The effects of intraocular lidocaine on the corneal endothelium. Ophthalmology 1998; 105:125–30. 37. Britton B, Hervey R, Kasten K, et al. Intraocular irritation evaluation of benzalkonium chloride in rabbits. Ophthalmic Surg 1976;7:46 –55. 38. Hoffman RS, Fine IH. Transient no light perception visual acuity after intracameral lidocaine injection. J Cataract Refract Surg 1997;23:957– 8.
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Originally received: December 15, 1997. Revision accepted: June 1, 1998. Manuscript no. 97853. From the Department of Ophthalmology, College of Medicine, National Cheng Kung University, Tainan, Taiwan, Republic of China. The authors have no proprietary interest in the development or marketing of any device or medications mentioned in the article or any competing device. Address correspondence and reprint requests to Sung-Huei Tseng, MD, C-6-1 No. 61 Shaw Dong Road, Tainan, Taiwan, R.O.C.
acting anesthetic agents and less-invasive methods of its administration can now be used. Topical anesthesia alone for cataract removal and IOL implantation was first proposed by Fichman (Fichman RA, MD. Phacoemulsification with Posterior Chamber IOL Can Be Performed with Use of Topical Anesthesia. Presented at the Symposium on Cataract, IOL and Refractive Surgery, San Diego, April 1992). This anesthetic technique has been increasingly accepted as the number of surgeons performing clear corneal phacoemulsification increases.18 –25 Unlike injection of anesthetic agents, topical administration of anesthetic agents is associated with minimal discomfort. The risk of ptosis and bruising is nonexistent and that of injuring ocular tissues or causing life-threatening systemic side effects is minimal. It also has the advantage over other methods in that the vision is restored instantly after the operation and undesirable cosmetic side effects are altogether avoided. In addition to all of these advantages, the technique is economical. However, with topical anesthesia, the agent blocks only trigeminal nerve endings in the cornea and the conjunctiva,
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Ophthalmology Volume 105, Number 11, November 1998 leaving the intraocular structures in the anterior segment unanesthetized. Thus, manipulation of the iris or stretching of the ciliary and zonular tissues, which is inevitable during the surgery, could irritate the unanesthetized ciliary nerves and result in discomfort. This forced Fukasaku and Marron26 to abandon topical anesthesia in favor of peribulbar injection. More recently, increasing numbers of ophthalmologists administer anesthetic agents by intracameral injection or by adding an anesthetic agent to the irrigation fluid used during the intraocular phase of surgery.27,28 To investigate the efficacy of intracameral anesthesia, we designed a prospective, randomized, controlled trial comparing topically administered lidocaine with intracameral injection of balanced salt solution (BSS) or lidocaine in patients undergoing phacoemulsification and implantation of a foldable IOL.
Patients and Methods From January to July 1997, a total of 162 patients were eligible for phacoemulsification surgery and implantation of an IOL with topical anesthesia and gave written, informed consent to participate in the study. Patients were excluded from the study if they had a history of hearing impairment, dementia, movement disorder, or excessive anxiety; had poor fixation due to nystagmus, strabismus, or cataract; or were not native speakers of the language used in the documentation of informed consent. Other contraindications to participation in this study included known allergic response to lidocaine or other topical anesthetic agents and corneal or ocular conditions precluding the use of topical anesthesia. A random numbers table was used to assign each patient entering the study to either group 1 (n ⫽ 81) or group 2 (n ⫽ 81). All patients in both groups received a minimum total of five doses of topical anesthesia for phacoemulsification and implantation of a 6.0-mm-diameter foldable silicone IOL (AMO Model SI-30NB; Allergan, Irvine, CA). In addition, all patients received an intracameral injection immediately after entrance into the anterior chamber, but only patients in group 2 received an injection that contained the active anesthetic agent.
study. First, a corneal groove of 300 m in depth and 3.2 mm in length was fashioned at the temporal limbus. Then, a 1.5- to 2-mm-long corneal tunnel was made with a crescent knife (No. 1118; Visitec, Sarasota, FL). Finally, after creation of a sideport incision at the 2-o’clock position to the left of the main incision, a slit knife (Surgical Specialties Co. REF 72-2561; Reading, PA) was used to penetrate Descemet membrane, with a downward pressure at the tip of the knife, resulting in a 2.5-mm internal valve. For patients in group 2, 0.5 ml of 1% preservative-free lidocaine (an equal-volume mixture of 2% lidocaine and BSS) was injected slowly through the incision into the anterior chamber. For patients in group 1, who served as control subjects, the same technique was used to inject 0.5 ml of BSS as a placebo. The anterior chamber was then filled with a viscoelastic substance (Viscoat; Alcon, Humacao, Puerto Rico). A continuous curvilinear capsulorhexis was performed with capsule forceps while the eyeball was immobilized with a 0.12-mm forceps. This was followed by hydrodissection, hydrodelineation, phacoemulsification with the divide-and-conquer technique, and then instrumental removal of residual lens cortex. The length of the incision then was extended to 3.2 mm to permit insertion of a 6.0-mm foldable IOL. Shortly after positioning of the IOL, carbachol 0.01% (Miostat; Alcon Surgical, Ft. Worth, TX) was injected to constrict the pupil. The viscoelastic substance was aspirated, and BSS was injected at the entrance of the corneal tunnels for hydration of the stroma. The wound was tested for leakage of fluid by gentle compression with a Merocel sponge, and none of the patients required a suture to close the wound. Finally, one drop of 5% povidone–iodine solution was instilled into the conjunctival sac before the lid speculum was removed.
Patient Evaluations of Pain At the completion of the operation, each patient was shown a visual analogue pain scale with numeric and descriptive ratings from 0 (“no pain”) to 10 (“maximum pain”), as described by Stevens.29 Patients were asked to use this 10-point scale to rate the level of pain felt during the operation, including pain felt after delivery of topical and intracameral agents. If patients were unable to read the printed numbers and descriptive text on the pain scale, the examiner read them to the patient. In addition, we recorded any verbal expression of pain that patient made during the operation (e.g., with manipulation of the iris).
Technique of Topical Anesthesia Patients were given oral fludiazepam (Erispan; Sumitomo Pharmaceutical, Osaka, Japan), 0.5 mg, and acetaminophen, 1.0 g, 1 hour before surgery. Ten minutes before the surgery, two drops of unpreserved, methylparaben-free lidocaine 2% (Xylocaine; Fujisawa Pharmaceutical, Osaka, Japan) were instilled into the superior and inferior cul-de-sacs. This was followed by additional two-drop doses into the cul-de-sacs at 5 minutes and immediately before the start of surgery. Intraoperatively, two-drop doses of lidocaine were administered onto the ocular surface immediately before commencement of phacoemulsification and before implantation of the IOL. Additional doses were given if the patient gave indication of discomfort during the procedure or when the procedure was prolonged.
Surgical Procedure and Intracameral Anesthesia All surgical procedures were performed by one surgeon (SHT). Temporal clear corneal incision was made using a “three-plane” technique while the eyeball was immobilized with a Thorton–Fine ring. Rectus bridle sutures were not used in the operations in this
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Statistical Analysis Student’s t test for two samples was used to compare characteristics of the two study groups. To evaluate differences between the pain scores of the two groups, the Mann–Whitney U test was used because the data were not normally distributed. Statistical analyses were performed using the StatView statistical package (Abacus Concepts Inc, Berkeley, CA). The null hypothesis was rejected if the P value was less than 0.05.
Results The average age of all patients in the study was 67.2 ⫾ 7.9 years (range, 43– 84 years) and approximately 60% were female (Table 1). Differences between the two study groups in age and gender distribution were not statistically significant (P ⫽ 0.13). None of the patients in the study experienced complications due to the method of anesthetic administration or drug toxicity that were severe enough to interfere with continuation of the operation.
Tseng and Chen 䡠 Intracameral Anesthesia for Cataract Surgery Table 1. Characteristics of 162 Patients Randomly Assigned to Receive Topical Lidocaine with or without Intracameral Lidocaine for Phacoemulsification and Intraocular Lens Implantation
Characteristic Age (yrs) (mean ⫾ SD) Range Female (%) Pain score (scale of 0–10) Mean Range
Group 1: Group 2: Intracameral BBS Intracameral Lidocaine (n ⴝ 81) (n ⴝ 81) 66.1 ⫾ 7.7 46–83 59.3 0.63 ⫾ 0.68 0–3
67.8 ⫾ 7.9 43–84 62.3 0.37 ⫾ 0.58 0–4
BSS ⫽ balanced salt solution; SD ⫽ standard deviation.
No one in either study group reported discomfort beyond mild stinging with topical administration of anesthetic, and none experienced operative discomfort sufficient to warrant supplemental peribulbar anesthesia or intravenous sedation. All patients expressed satisfaction with the anesthesia for their surgery. In eyes with small pupils (two eyes in group 1 and three eyes in group 2) due to diabetes or prolonged use of miotics, sphincterotomy and pupiloplasty were performed to facilitate phacoemulsification. Furthermore, in one patient from group 2, the surgery was complicated by a small posterior capsule rupture and loss of vitreous intraoperatively. However, this patient was able to tolerate a mechanical, anterior vitrectomy without supplemental retrobulbar or peribulbar anesthesia. Finally, a foldable IOL was implanted into the capsular bag in this eye without difficulty. Because topical and intracameral instillation of anesthetic drugs cannot achieve akinesia, some patients exhibited a strong blink–Bell’s phenomenon during the operation. When this occurred, the “psycholinguistics” technique described by Fichman24 was used and environmental light intensity and other stimuli were decreased to calm the patient and improve his or her ability to concentrate on the microscope light. The pain scores reported by patients after surgery are shown in Figure 1. Seventy-three patients in group 1 (90%) and 77 patients in group 2 (95%) reported no pain (a score of 0) or only minimal discomfort (a score of 1), and none of the patients reported a pain score of 5 or above (Fig 1). The mean pain score in group 1 (control subjects) was 0.63 ⫾ 0.68, and in group 2, it was 0.37 ⫾ 0.58. The difference between the mean pain scores for the two groups was statistically significant (P ⫽ 0.0053). During surgery, approximately 15% of patients in group 1 verbalized discomfort, usually with manipulation of the iris, sudden distention of the anterior chamber by irrigating fluid after introduction of the phacoemulsification tip, or hydrodissection or rotation of the nucleus. Some patients even verbalized discomfort on administration of Miostat. The most severe pain expressed was during the use of a spatula to reposition a prolapsed iris. A smaller proportion of patients in group 2 (2.5%) reported ocular discomfort during such manipulations, although most described a sensation of “abrupt ocular soreness” when lidocaine was injected intracamerally. Such discomfort generally lasted for only a few seconds.
Discussion Since 1993, when Kershner first reported the advantages of topical anesthesia in scleral pocket phacoemulsification,18 a
number of reports favoring this methodology have appeared.19 –25 In one study, in which topical anesthesia was used in one eye and retrobulbar injection in the other eye of the same patient, 61.5% of patients selected topical over retrobulbar injection as the preferred method of anesthetic administration.25 However, in the 1995 annual survey of the American Society of Cataract and Refractive Surgery, only 8% of responding members indicated a preference for topical anesthesia over posterior orbital injections for patients undergoing cataract surgery, which was only a slight increase from 4% in 1993 and nearly 0% in 1992.30,31 In addition, when Fukasaku and Marron26 compared topical with retrobulbar anesthesia, they found more intraoperative pain with the topical approach. The problem may be related to the limited ability of topical anesthetic agents to penetrate the ocular tissues. To achieve analgesia during intraocular surgery, impulses in pain fibers exiting the eye must be blocked completely, including impulses in the long sensory fibers from the cornea, the iris, and the ciliary body to the ciliary ganglion. Failure of topical anesthesia to block sensations in all these fibers makes intraoperative manipulation of the iris particularly uncomfortable for patients undergoing intraocular procedures with topical anesthesia only. Various techniques have been advocated to alleviate patient discomfort associated with intraocular manipulation. Grabow20 emphasized the importance of adequate cycloplegia to minimize stretching of zonules and the ciliary muscle, and Novak and Koch23 recommended lowering of the irrigating solution bottle to minimize the hydrostatic pressure that could cause pain by stretching the ciliary body. Early in the development of techniques for topical anesthesia for phacoemulsification, intravenous sedation was often used as an adjunct.18,20 –23,25,32 None of the patients in our series required this intervention, and the mean pain scores of 0.63 and 0.37 for patients in group 1 and group 2, respectively, were similar to the mean pain score of 0.41 reported by Patel and associates25 for patients in their study. We believe that the low level of discomfort in our patients, even in the placebo group, may be explained by the speed with which we performed phacoemulsification and the caution we exercised during intraocular manipulation.
Figure 1. Number of patients reporting pain scores of 0 (‘‘no pain’’) to 10 (‘‘worst pain’’) during phacoemulsification and implantation of a foldable intraocular lens. Black bars ⫽ topical anesthesia only; white bars ⫽ combined topical and intracameral anesthesia.
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Ophthalmology Volume 105, Number 11, November 1998 Intracameral Instillation of Anesthetic Agent Although the majority of patients in both groups in our study experienced no or only minimal discomfort intraoperatively, the difference in mean pain scores for the two groups was statistically significant. The efficacy of intracameral block was particularly striking when intraocular manipulation was required. Patients who received only topical anesthesia were more likely to experience discomfort during iris manipulation, zonular stretching, and spasm of the ciliary body induced by injection of Miostat. In contrast, patients who received intracameral anesthesia as well as topical lidocaine were practically oblivious to such manipulations. One would expect the pain to be particularly intense with the group 2 patient who required immediate anterior vitrectomy for rupture of the posterior capsule. However, he was able to tolerate the procedure and later rated the pain as only mild to moderate (a score of 4), although he was anesthetized only with topical and intracameral instillation of lidocaine. Our observations seemed to agree with those of Gills et al27 and Koch,28 who recently reported that irrigation of the anterior chamber with unpreserved lidocaine alleviated the intraocular discomfort of some patients undergoing cataract extraction and implantation of an IOL while under topical anesthesia. We also noticed that intracameral anesthesia was particularly effective in reducing patient discomfort when synechiolysis or sphincterotomy was required or iris retractors were used to enlarge the pupil.
Adverse Effects of Intracameral Injection of Lidocaine Despite the efficacy of supplementary intracameral lidocaine, nearly all patients in group 2 experienced abrupt and very transient ocular discomfort immediately after the injection into the anterior chamber. This sensation may result from the direct irritation of the tissues caused by the lidocaine. A word of warning was sufficient to ward off the patient’s anxiety.
Contraindications to Intracameral Injection of Lidocaine Contraindications to the combined approach are similar to contraindications to topical administration of anesthesia alone. For example, the combined approach is not suitable for patients with a high degree of anxiety, those with hearing difficulties or mental retardation, or patients with an opaque cataract, as they cannot fixate on the operating microscope light.
Toxic Effects of Intracameral Lidocaine There is a concern that intracameral injection of an anesthetic agent may cause intraocular injury, particularly to the corneal endothelium and the retina. Toxic effects of the commonly available topical anesthetic agents on the corneal epithelium have been studied extensively,33 but little is known of their toxic effects on corneal endothelium. A
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report of several cases in which inadvertent injection of lidocaine into the anterior chamber had no ill effects supported the hypothesis that routine intraocular injection of this local anesthetic may be safe and effective as part of the anesthesia regimen.34 In contrast, a recent study in a rabbit model35 found that injections of unpreserved lidocaine hydrochloric acid 4% into the anterior chamber for days produced significant corneal thickening and opacification, from which the authors concluded that topical anesthetic agents should not be allowed to reflux into the anterior chamber. However, in the same study, injection of a diluted (1:10) solution of unpreserved lidocaine failed to produce any significant increase in corneal thickness or opacification in the rabbits. Furthermore, Kim et al36 evaluated the direct effect of preservativefree lidocaine hydrochloric acid 1% on the corneal endothelium using an in vitro perfusion system, and their results showed that lidocaine hydrochloric acid 1% only caused the endothelium of human and rabbit corneas a transient edema. In the clinical setting in which lidocaine was intracamerally injected, the amount of the anesthetic agent and the time it was in contact with corneal endothelium before being flushed from the eye were negligible compared to a study conducted on rabbits. We consider that such brief exposure to lidocaine is unlikely to injure the corneal endothelium. Of note, however, is the finding of another study in rabbits that the preservatives, such as benzalkonium chloride at a concentration of 0.025% to 0.05% in commercially available anesthetic agents, may cause irreversible damages to the corneal tissues.37 Only unpreserved lidocaine should be used for intracameral injection. In support of our conclusion, Gills et al27 also found no evidence of significant endothelial cell loss or injury in patients who received intracameral injections of unpreserved lidocaine. Our slit-lamp biomicroscopic examination showed no evidence of corneal pathology, edema, thickening, or other toxicity, nor did any patients in our study have unexplained iritis or other unusual intraocular inflammation develop. Even in a study in which transient visual loss occurred in a patient receiving intracameral injections of lidocaine, vision recovered completely within hours with no untoward effects.38 The transient visual loss in this case probably was caused by effects of the topical anesthetic agent on the retinal nerve fiber layer, in turn because of lack of the barrier effect of posterior capsule, zonules, and vitreous humor. Incidentally, therefore, the retina must be resistant to toxic effects of low concentrations of intracameral unpreserved lidocaine. Thus, currently, unpreserved intracameral lidocaine seems to be safe for the cornea, the anterior chamber, and the retina, although a larger series of evaluations is called for before a definite conclusion can be drawn. In conclusion, combining topical and intracameral anesthesia for cataract surgery offers significant benefits over topical anesthesia alone in terms of patient comfort. We believe that the combined topical–intracameral approach will probably become the standard ophthalmic anesthetic technique in phacoemulsification.
Tseng and Chen 䡠 Intracameral Anesthesia for Cataract Surgery
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