Ophthalmic surgeons have witnessed a significant evolution in surgical techniques for cataract extraction in the 20th century.1 The most remarkable advance is the significant decrease in the incision size. Cataract surgery using phacoemulsification through a small, clear corneal, self-sealing incision avoids cauterization, suturing, and intraocular pressure fluctuations. Moreover, this technique is faster, more controlled, and less traumatic than conventional large incision extracapsular cataract extraction. With the phakonit technique, it is possible to remove the cataract through a 0.9 mm incision.2
Anesthesia techniques for cataract surgery have also advanced significantly. Except for a few earlier reports of the use of topical cocaine, general anesthesia was preferred in the early years.3,4 This was followed by various methods of injectable anesthesia including retrobulbar, peribulbar, sub-Tenon's, and subconjunctival.3,4 Because of marked improvements in surgical techniques, it is no longer essential to achieve complete akinesia of the eye. As a consequence, topical anesthesia has evolved into a relatively popular technique. The topical technique includes eyedrop application,5–9 sponge anesthesia,10 eyedrops plus intracameral injection,11–20 and most recently gel application.21,22 In a 2000 survey, 49% (range 37% to 62%) of members of the American Society of Cataract and Refractive Surgery in the United States stated a preference for topical anesthesia23; as many as 82% of those using topical anesthesia preferred eyedrops in association with an intracameral injection of lidocaine.
However, neither injectable nor topical anesthesia is completely safe. Injecting anesthetic agents can lead to complications that are sight threatening and in rare cases, life threatening.3,4,24,25 Topical anesthesia prevents these complications but has been reported to cause corneal epithelial, corneal endothelial, or retinal toxicity (“Topical Anesthesia Side Effect Is Less Likely with Intact Capsular Bag,” Ocular Surgery News, November 1, 1996, page 32). The toxicity is mostly the result of the preservatives in the anesthetic solutions.26–30
Clear corneal phacoemulsification and intraocular lens (IOL) implantation without the use of an anesthetic agent has been reported in India,31 Germany (T. Neuhann, MD, “No Anesthesia Cataract Surgery Can Be an Option,” Ocular Surgery News, Europe/Asia-Pacific Edition, November 1, 2000, pages 13–17), Spain (F.J. Gutierrez-Carmona, MD, PhD, et al., “Phacoemulsification with Cryoanalgesia: a New Approach for Cataract Surgery,” video presented at the American Academy of Ophthalmology annual meeting, Dallas, Texas, USA, October 2000), and Brazil (V. Centurion, MD, “No-Anesthesia Cataract Surgery Defies Conventional Wisdom,” Ocular Surgery News, January 15, 2001, pages 9–15). We completed a study comparing the pain scores of patients having clear corneal phacoemulsification under no anesthesia, topical anesthesia, or topical plus intracameral anesthesia. We also compared patient discomfort and surgeon stress level during surgery.
Patients and methods
This prospective randomized double-masked study comprised 75 patients who had clear corneal phacoemulsification with foldable IOL implantation from August 1999 to October 1999. The patients were between 38 and 79 years old. Cataract density ranged from grade 2 to 4 (Emery-Little classification).32 Patient data are shown in Table 1.
Excluded were patients with barriers to communication or cooperation during surgery (eg, extreme anxiety, language/hearing impairment, mental retardation, dementia, Parkinson's disease, very young). Monocular patients and those with hard, mature cataract (Emery-Little grade 5), a shallow anterior chamber, a fully dilated pupil diameter less than 5.0 mm, and unable to understand a visual analog pain scale were also excluded.
After receiving a detailed explanation of the study, all patients provided informed consent. The study was reviewed and approved by the local ethics research committee of the hospital.
The patients were randomized to 1 of 3 groups of 25 patients each based on the type of anesthesia. Group 1 received no anesthesia; Group 2, topical anesthesia; and Group 3, topical plus intracameral anesthesia.
No patient received preoperative or intraoperative sedation. Preoperatively, the pupils were dilated with phenylephrine 5%, cyclopentolate 0.5%, and tropicamide 1% eyedrops. No nonsteroidal antiinflammatory drugs were used.
While still in the preoperative area, patients in Group 1 received 2 drops of balanced salt solution (BSS®) every 5 minutes 3 times beginning 10 to 15 minutes before surgery. The corneal endothelium was coated with a viscoelastic agent before the capsulorhexis was created. An intracameral injection of BSS was given using a 25-gauge Rycroft cannula (Beaver and Visitec Products). Patients in Group 2 received lidocaine 4% eyedrops preoperatively and an intracameral injection of BSS as in Group 1. Patients in Group 3 received preoperative lidocaine 4% eyedrops and an intracameral injection of preservative-free lidocaine 1%.
A protocol was established for supplemental anesthesia for breakthrough pain during the surgery. If the patient reported pain, 2 additional drops of lidocaine 4% were placed in the eye. If the pain persisted, a peribulbar or retrobulbar block was used.
All cataract surgeries were performed at a referral institute in southern India by the same surgeon (Am.A.). A speculum with solid blades was used in all cases. The patients were asked to look down. No superior rectus sutures were used in any group. Patients were informed that they would be aware of the sensation of touch and would be able to move their eyes. The operating microscope light was kept at its lowest level, with the intensity gradually increased to the usual operating level after hydrodissection. Patients were encouraged to fixate on the microscope light during surgery.
Figure 1 shows the steps of the surgical technique. First, sodium hyaluronate 1% (Healon®) was injected into the anterior chamber with a 26-gauge needle (Figure 1,A) to distend the eye and a self-sealing corneal valve was created. A straight rod was used to enter the anterior chamber through the same opening to stabilize the eye during the procedure; a 3.2 mm groove was made in clear temporal cornea with a diamond knife (Figure 1,B). No toothed or fixation forceps was used to grasp the conjunctiva at any time. A 5.0 to 5.5 mm wide capsulorhexis was created with a 26-gauge bent needle cystotome (Figure 1,C). Complete cortical cleaving hydrodissection was performed by injecting BSS between the lens capsule and cortex with a 27-gauge cannula. Nuclear emulsification (Master 10,000 unit, Alcon) was performed using the central anterior chopping (karate chop) technique31 but with less ultrasound power (Figure 1,D).
After meticulous cortical cleanup, the capsular bag was filled with a viscoelastic material. A single-piece, plate, foldable silicone IOL with large holes (Staar Surgical Co.) was then implanted (Figure 1,E). The viscoelastic material was removed from the anterior chamber and capsular bag by irrigation/aspiration (I/A). The corneal incisions were secured by stromal hydration (Figure 1,F). No sutures were required in any case.
No patient received intracameral miotics during surgery. None received a subconjunctival injection or eye pads at the completion of surgery.
After surgery, the patients were taken to the postoperative area, where vital signs were obtained. Patients used a standard 10-point visual analog scale33 to assess their intraoperative pain. The scale was administered in the recovery room immediately after surgery by a theater nurse trained in its use. Standardized phrasing was used throughout. The surgeon was not present in the recovery room during this assessment.
Patients were asked to mark the scale at the point most accurately representing the worst degree of pain experienced during surgery. If the patient was unable to see the scale or read the accompanying text, the scale was described and a verbal score obtained. Patients were also asked to differentiate the sensation as pain or discomfort versus touch or movement. The discomfort during the surgery and related to the operating microscope light was assessed as none (0), a little (1), or a lot (2). Surgeon stress during the surgery was rated from 0 to 2, and the total surgical time (minutes) was noted. The patients were kept in the recovery area for a minimum of 30 minutes. The surgeon also completed a questionnaire on surgical conditions, complications, and the need for supplemental anesthesia.
Comparison of parameters among the 3 groups was by an analysis of variance. A P value less than 0.05 was considered statistically significant.
There was no significant difference in age and cataract density among the 3 groups (P = .417 and P = .399, respectively). The surgical time was slightly longer in the topical anesthesia group than in the no-anesthesia or topical plus intracameral anesthesia groups; however, the difference was not significant (P = .483). No patient in any group required supplemental anesthesia.
The results of the questionnaires are shown in Table 2. The mean intraoperative pain score (scale 0 to 10) in the no-anesthesia group was slightly higher than in the topical and topical plus intracameral groups. However, the difference was not statistically significant (P = .610). The mean patient discomfort score during surgery was significantly higher in the no-anesthesia group (P = .0235) than in the other 2 groups. The mean score for patient discomfort from the microscope light was slightly higher in the no-anesthesia group; however, the difference was not statistically significant (P = .211). The surgeon's stress was significantly greater in the no-anesthesia group than in the other 2 groups (P = .0206).
Topical anesthesia is now a preferred technique in cataract surgery. Clear corneal phacoemulsification has the advantage of avoiding touching superficial sensitive ocular tissue other than the peripheral cornea during the surgery. Preserved ocular motility can be used to improve the operating conditions by optimizing the red reflex and wound access. The topical approach avoids the risks of regional anesthetic techniques (eg, peribulbar) including globe perforation and does not require orbital decompression to decrease vitreous pressure.25 In addition, there is no effect on the optic nerve blood flow. Postoperatively, recovery is quicker and pain is reduced. Also, many patients prefer the topical technique.
Although topical lidocaine alone provides adequate anesthesia for phacoemulsification and foldable IOL implantation, studies11,12 report that combined topical and intracameral administration of lidocaine further minimizes intraoperative discomfort. In a prospective randomized double-masked clinical trial, Gillow et al.19 evaluated the efficacy of supplementary intracameral lidocaine in routine phacoemulsification under topical anesthesia. Patients were randomly allocated to receive topical anesthesia plus 0.5 mL intracameral BSS or topical anesthesia plus 0.5 mL preservative-free lidocaine 1%. Intraoperative and postoperative discomfort and the discomfort caused by the microscope light were assessed. Although there was a small reduction in discomfort from the microscope light when intracameral lidocaine was used, there was no significant relationship between the use of intracameral lidocaine and the intraoperative or postoperative pain scores. The authors conclude that the routine use of intracameral lidocaine as a supplement to topical anesthesia has no clinically useful role.
Topical anesthesia has many advantages over injectable anesthetic techniques.34,35 However, in a few cases, it has led to corneal epithelial, corneal endothelial, or retinal toxicity that is mainly the result of the preservatives in the anesthetic solutions.24,26–30 In rare cases, the topical anesthetic agent and its vehicle may serve as a reservoir of microbial contamination with the potential to cause infection. Some agents (eg, proparacaine) can lead to allergic and idiosyncratic reactions such as periocular swelling, erythema, and contact dermatitis.26 In addition, preoperative instillation of some topical anesthetic agents (eg, lidocaine) can cause burning and stinging, and multiple applications can lead to mild corneal haziness during surgery. There is a potential for cumulative toxicity because several doses of the agent are administered. Recent reports recommend that cataract surgeons be aware of the potential for endothelial injury if anesthetic agents are injected into the eye.28–30 This is not surprising because the intraocular concentration of the anesthetic agent after intracameral injection can be 250 times higher than the concentration after topical application.30 The toxicity of ocular anesthetics has been reported and discussed in several studies.26–30
Clear corneal phacoemulsification surgery without topical anesthesia was first done in India in June 1998.31 Our study is the first randomized double-masked controlled trial comparing 3 techniques: no anesthesia, topical anesthesia, and topical plus intracameral anesthesia. No patient in any group required supplemental anesthesia or had an intraoperative complication. This may be because the surgery was atraumatic and performed without touching the conjunctiva with a toothed forceps. In addition, the patients were motivated and the surgeon was experienced and skilled.
In our study, there was no significant difference in intraoperative pain scores among the no-anesthesia, topical anesthesia, and topical anesthesia with intracameral lidocaine groups. Assessments of parameters other than the pain scores revealed that patient discomfort and surgeon stress during the procedure were significantly higher in the no-anesthesia group than in the topical and topical plus intracameral lidocaine groups. These 2 findings are probably correlated; that is, the greater the discomfort, the less the patient cooperates, causing more stress for the surgeon.
It seems surprising that cataract surgery can be performed through one of the most sensitive structures (cornea) without using anesthesia. Although there may be a minimal placebo or hypnotic effect when surgery is done without anesthesia, our surgeon did not continuously talk to or assure patients (eg, provide vocal anesthesia) at any time during surgery. No patient was told that a placebo eyedrop would be instilled, nor did the surgeon or his team continuously use hypnosis or vocal anesthesia. The precise reason for this phenomenon remains unknown to us. However, we can advance hypotheses related to surgical and anatomic factors.
The surgeon's skill and experience are important factors in successful no-anesthesia cataract surgery. It is important to avoid grasping the conjunctiva or sclera with a toothed forceps. The surgeon should also use a straight and relatively blunt rod to stabilize the eye during the entire procedure. The creation of a clear corneal incision avoids the need for cautery, which is necessary to achieve hemostasis with scleral tunnel incisions. Other important factors in successful topical and no-anesthesia techniques include the gradual increase in microscope luminance and minimal intraocular and iris manipulation. The phaco power should be kept as low as possible to avoid excessive heating of the phaco tip, which can produce pain.
Concerning the anatomic factors, the cornea is supplied by the medial and lateral long ciliary nerves, which are branches of the trigeminal nerve. It is sensitive to touch, pain, and temperature.36 However, there are marked topographical variations in corneal sensitivity. In addition to diurnal fluctuations, corneal sensitivity varies by age, sex, and race.36–38 The central part of the cornea is the most sensitive, with an overall reduction from the center to the periphery. The superior cornea is the least sensitive, probably because of difference in the density of the innervational network. The density of this network is highest in the center of the cornea, encompassing an area 5.0 mm in diameter. The density decreases toward the limbus. There are more free nerve endings in the horizontal meridian than in the vertical one.36
Concerning diurnal variations, corneal sensitivity is lowest in the morning and highest in the evening. The decreased sensitivity in the morning may be attributed to a reduction in oxygen tension at the epithelium surface when the eye is closed.38
Corneal sensitivity remains practically unchanged from 10 to about 50 years of age. Subsequently, the decline is significant, reaching one half after 65 years of age.36 The precise mechanism is not clear; however, some authors relate it to the formation of arcus senilis and to a decreased concentration of acetylcholine. In women, corneal sensitivity decreases during the premenstrual and menstrual periods.
The role of race should not be underestimated.37 Many studies have confirmed that corneal sensitivity is 4 times less in dark-eyed, nonwhite persons (eg, Indians, Chinese, blacks) than in light-eyed white persons. This phenomenon is relevant in contact lens use.37
Similarly, it is possible that different quantities of anesthetic agents may be needed according to eye color. This agrees with the clinical fact that more ocular drugs are needed in eyes with dark irides than in those with light irides to obtain the same effect (eg, cycloplegia). The reason is not known, although it may be related to the amount of melanin present in the iris. The cornea contains no pigment, so explaining the diminution in corneal sensitivity in eyes with darker irides is difficult. It is not known whether corneal thickness varies with eye color. It has been shown that corneas that are relatively thick as a result of edema are less sensitive than normal corneas. It is also unknown whether the nerve supply density varies by race and eye color. Another possibility is that the difference in sensitivity arises in the central nervous system and not at the periphery. Finally, recent studies report that frequent exposure to ultraviolet (UV) rays (between 280 and 310 nm) decrease corneal sensitivity by as much as 73%.36
Clear corneal phacoemulsification without topical anesthesia has been performed by others in India (M. Rajan, “How No Anesthesia Cataract Surgery Works,” presented at the All India Ophthalmology Congress, Chennai, India, January 2000). One surgeon performed more than 450 cases in India using this technique (K.R. Mehta, MD, personal communication, February 2000). However, approximately 10% to 12% of patients required supplemental anesthesia. Gutierrez-Carmona performed no-anesthesia cataract surgery in 13 patients in Spain39 (F.J. Gutierrez-Carmona, MD, PhD, personal communication, February 2000). He used cooled viscoelastic solution and BSS in the operative eye and termed the technique cryoanalgesia. Neuhann performed no-anesthesia cataract surgery in 16 cases in Germany (T. Neuhann, MD, “No Anesthesia Cataract Surgery Can Be an Option,” Ocular Surgery News, Europe/Asia-Pacific Edition, November 1, 2000, pages 13-17). Although motivation is important, Neuhann's experience indicates that no-anesthesia cataract surgery works better in older patients. The technique has also been performed in Sweden (M. Zand, MD, “No Anesthesia Cataract Surgery,” presented at the All India Ophthalmology Congress, Chennai, India, January 2000) and Brazil (V. Centurion, MD, “No-Anesthesia Cataract Surgery Defies Conventional Wisdom,” Ocular Surgery News, January 15, 2001, pages 9-15).
In conclusion, our results indicate that no-anesthesia cataract surgery succeeds when the technique is atraumatic and performed in suitable patients by an experienced, skilled, and confident surgeon. Incisions and manipulations through the least sensitive (superior) part of the cornea are probably the most important factors. A further decrease in corneal sensation due to racial factors and long-term exposure to UV rays probably accounted for our results.
The results of our preliminary study must be interpreted with caution. We are not recommending the no-anesthesia clear corneal phacoemulsification technique for every cataract surgeon or every patient because of the simplicity and low cost of currently available topical anesthetic agents. Although the mean pain scores were similar among our 3 groups, the use of at least topical anesthetic with or without intracameral lidocaine seems to increase patient and surgeon comfort during surgery. Alternatively, the use of a cooled eyepad, irrigating solution, and viscoelastic material (cryoanalgesia) may help reduce patient pain and discomfort during the cataract surgery without the possible adverse effects of topical and/or intracameral anesthetic agents.
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