Purpose
To compare pain scores with and without supplementary topical 2% lidocaine gel in patients undergoing simultaneous bilateral laser-assisted in situ keratomileusis (LASIK) under topical anesthesia using 0.5% proparacaine eye drops.
Design
Randomized double-masked placebo-controlled trial.
Methods
Fifty-one Chinese subjects (102 eyes, with 51 eyes in each arm) were included. One eye was randomly allocated to have supplementary 2% lidocaine gel while the other eye received carbomer gel as control, in addition to topical 0.5% proparacaine. The pain scores for each eye during microkeratome flap creation, during laser ablation, and at 15, 30, and 45 minutes after LASIK were assessed. An overall pain score of the LASIK procedure was also obtained. Primary outcome measures were pain scores during and after LASIK. Secondary outcomes included need for additional topical anesthesia, patient cooperation score, and duration and complications of surgery.
Results
In the 2% lidocaine gel–treated group, the pain scores were significantly lower during microkeratome flap creation and laser ablation, and postoperatively at 30 and 45 minutes ( P < .05 for all). Patients in the lidocaine gel group required less additional topical anesthesia ( P = .0004) and were more cooperative ( P = .019) as compared to the carbomer gel group. No surgical or postoperative complications were observed.
Conclusions
The use of supplementary 2% lidocaine gel in LASIK is effective in lowering the pain experienced during and up to 45 minutes after LASIK.
Laser-assisted in situ keratomileusis (LASIK) is currently the most commonly performed refractive surgery because of its safety, efficacy, and accuracy. An important advantage of LASIK is reduced pain experienced during and after the procedure when compared to photorefractive keratectomy (PRK). However, some patients complain of discomfort or disabling pain during the surgery and in the early postoperative period. Intraoperative pain could make the patient uncooperative and increase risks of surgery. Blepharospasm attributable to postoperative pain could result in flap dislodgement. While the effects of anesthesia in patients with PRK have been extensively studied, the same is not true for LASIK. LASIK is currently performed using topical anesthetic drops in most patients, since the loss of fixation that results from orbital or general anesthesia interferes with ablation centration on the patients’ visual axis.
We have previously reported that pain during LASIK under topical anesthesia is most likely attributable to irritation of the eyelid structures and manipulations of the ocular surface. Patients experienced more pain at the time of placement of the speculum and during microkeratome flap creation. We postulated that the short duration of action of topical anesthetics and increased manipulations of the eyelids during LASIK in Asian eyes with smaller palpable fissures were possible reasons for pain during surgery.
The superior efficacy of lidocaine gel in ocular surface anesthesia has been previously demonstrated in patients undergoing cataract surgery. Compared to eye drops, the viscous gel–based vehicle improves contact and absorption at the ocular surface and prolongs its anesthetic action. For these reasons it may also be more effective in achieving lid margin anesthesia, especially the marginal and distal palpebral conjunctiva. We hypothesized that these effects may also benefit patients undergoing LASIK under topical anesthesia. Reduction in pain during LASIK surgery may subsequently increase the overall safety of the procedure.
In order to study the efficacy and safety of supplementary lidocaine gel during LASIK, we conducted a randomized double-masked placebo-controlled trial in patients undergoing simultaneous bilateral LASIK.
Materials and Methods
Fifty-one consecutive Chinese patients undergoing simultaneous bilateral LASIK were recruited for the study. The sample size calculation was based on previous pain score study done at our center. Inclusion criteria included age greater than 18 years, LASIK for the treatment of refractive errors using topical anesthesia, and willingness to participate in the study and provide assessment of pain scores. The exclusion criteria included patients with other ocular or systemic disorders, regular use of analgesics, and anisometropia over 1.5 diopters (D). All procedures were performed in the LASIK surgery center of the Chinese University of Hong Kong, Hong Kong, between June 2007 and January 2010, by experienced refractive surgeons.
Sample Size Calculation
In a previous study done at our center using proparacaine eye drops, the overall mean pain score during LASIK was 1.6 ± 2.2. In our clinical experience the pain score using lidocaine gel was much lower. The present study compared 2 groups where the anticipated difference in the pain score was 0.8 and the anticipated standard deviation was 2.2. The sample size required to achieve a type I error of 0.05 (α = 0.05) and a power of 80% (β = 0.20; power = 1 − β = 0.80) was 45 eyes in each group. We planned to recruit extra patients in anticipation of excluding a few unsuitable cases in the event of intraoperative complications that would have affected the pain scores substantially.
Randomization Method
All patients received topical proparacaine eye drops (Alcaine; Alcon, Fort Worth, Texas, USA) 3 times before surgery, at 5-minute intervals. The patients were randomized to receive carbomer gel (GenTeal Gel; Novartis, Hettingen, Switzerland) in the right eye and lidocaine gel (Xylocaine Jelly 2%, AstraZeneca, Södertäije, Switzerland) in the left eye in Group 1, and the order was reversed in Group 2 ( Supplemental Figure , available at AJO.com ). Right or left eyes were operated first with nearly equal frequencies in both groups. A dynamic allocation scheme was used to first create blocks of size divisible by 2, and simple randomization was then used to allocate patients to either Group 1 or 2. The block sizes were chosen randomly such that each block contained from 4 to 8 patients. A sealed envelope with the assigned treatment option was used to determine patient allocation after consent was obtained. The other eye of the same patient received the other treatment to act as an internal control.
Operative Procedure
Usual skin and eye preparations were done with 5% povidone-iodine before LASIK surgery. Draping of the lid margins was performed, taking care to ensure that the lashes and lid margins were isolated from the surgical field and eyelids were retracted using a lid speculum. At this juncture, the first pain score was obtained, after which an assistant applied the eye gels according to randomization, without informing the surgeon of the sequence of use. After a contact time of 2 minutes, the eye was rinsed using 30 mL balanced salt solution (BSS; Alcon, Forth Worth, Texas, USA) to remove all of the gel from the surface of the eye. LASIK surgery was performed using the Zyoptic XP microkeratome system with the 140-μm keratome head (Technolas, München, Germany) and either the Allegreto (Wavelight AG, Erlangen, Germany) or the Technolas (Technolas 217z) excimer laser platform. After completion of LASIK in the right eye, the procedure was repeated in the left eye, adhering to the same protocol as in the first eye.
Pain Scores
A verbal pain score (VPS) was employed. The patient was requested to rate the pain experienced on a scale of 0 to 10 after the stages of speculum placement, flap creation with microkeratome, and laser ablation. A pain score of 0 represented “no discomfort at all,” whereas a score of 10 represented “the worst pain that one can possibly imagine.” After the operation was completed and the speculum removed, the patient was requested to give an overall pain score for the whole procedure in that eye. Pain scores were also assessed at 15, 30, and 45 minutes after the procedure in each eye. All the scores were collected by a research assistant who was masked to the type of anesthesia received by the patient. The research assistant was a trained interviewer with experience in using the VPS during our previous LASIK pain score study.
Cooperation Score
At the completion of surgery, the surgeon, who was masked to the type of gel applied to each eye, was requested to give a score for the patient’s cooperation for each eye. A score of 0 represented “very cooperative patient who followed the surgeon’s instruction at all stages of the surgery.” A score of 10 represented “the most uncooperative patient you have ever met.” The scores were recorded by the same research assistant recording the VPS of the patient.
Statistical Analysis
Statistics were summarized and analyses were performed with SAS 9.1.3 (SAS Institute Inc, Cary, North Carolina, USA). Pain scores, patients’ cooperation, durations for suction, laser ablation, and total operation time were compared using the nonparametric Wilcoxon signed rank tests. Fisher exact test was used to compare the need of additional topical anesthetic between the groups. A P value <.05 was regarded as statistically significant for the assessment of patients’ cooperation. Bonferroni correction was used in the VPS analysis to address the issue of multiplicity with the statistical significance set at P < .005.
Results
Fifty-one patients (23 male, 28 female) were recruited. Mean age was 33.4 ± 7.6 years (range 19-47 years), and manifest spherical equivalent (SE) refraction was −7.61 ± 2.52 D in the eye receiving lidocaine gel and −7.65 ± 2.52 D in the eye receiving carbomer gel.
Table 1 shows the mean pain scores for each of the assessment stages for lidocaine gel– and carbomer gel–treated eyes. We assessed the first pain score after the placement of the speculum before the application of the gel and there was no significant difference between the groups ( P = .34). The most painful stage for both groups was flap creation with the microkeratome. At all stages of surgery, pain scores were significantly lower in the lidocaine gel–treated eyes ( Figure ). The overall intraoperative pain score was 4.37 for the carbomer gel group, indicating that LASIK with anesthetic drops was perceived as a procedure with some pain by the patient. The intraoperative pain was reduced significantly with the use of 2% lidocaine gel, as the average pain score was 3.06 ( P = .003). Three patients required additional instillation of 0.5% proparacaine eye drops to the lidocaine-treated eyes during surgery, in contrast to 18 carbomer-treated eyes ( P = .0004, Fisher exact test). Despite the application of topical proparacaine at the conclusion of surgery, the postoperative pain score was not negligible, and pain increased at 45 minutes postoperatively as shown in Figure 1 , although this increase was less in the lidocaine gel group ( P = .0004). There was no significant difference in duration of surgery between both groups ( Table 2 ).
| Speculum Placement a | Keratome Pass | Laser Ablation | Overall Score | 15 Minutes Postoperative | 30 Minutes Postoperative | 45 Minutes Postoperative | |
|---|---|---|---|---|---|---|---|
| Lidocaine gel | 1.90 ± 1.84 | 3.35 ± 2.30 | 2.18 ± 2.23 | 3.05 ± 1.97 | 1.06 ± 1.39 | 1.27 ± 1.48 | 1.35 ± 1.62 |
| Carbomer gel | 2.12 ± 1.70 | 5.31 ± 2.62 | 3.55 ± 2.35 | 4.37 ± 2.10 | 2.24 ± 2.37 | 2.26 ± 1.93 | 2.77 ± 2.22 |
| P value b | .34 | .0005 | .0019 | .0046 | .0064 | .0043 | .0007 |
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