|Year : 2021 | Volume
| Issue : 3 | Page : 311-315
Comparative study of intracameral lidocaine and topical mydriatics in pupil dilation during phacoemulsification
KK Shilpa Sunil, NV Latha
Department of Ophthalmology, Government Medical College, Kannur, Kerala, India
|Date of Submission||23-Mar-2021|
|Date of Decision||27-Mar-2021|
|Date of Acceptance||29-Mar-2021|
|Date of Web Publication||08-Dec-2021|
Dr. K K Shilpa Sunil
Department of Ophthalmology, Government Medical College, Pariyaram, Kannur - 670 503, Kerala
Source of Support: None, Conflict of Interest: None
Introduction: Intracameral injection of preservative-free lidocaine is used as an alternative to reduce the potential disadvantages of common mydriatics in cataract surgery. Aims and Objectives: The aim is to evaluate pupil dilation by an intracameral injection of lidocaine during phacoemulsification cataract surgery and compare the results with those using conventional topical mydriatics. Methods: A prospective cohort study was conducted in 60 consecutive patients undergoing phacoemulsification cataract surgery under topical anesthesia at Government Medical College, Kannur from July 2018 to December 2019. Patients were allocated to intracameral lidocaine or topical mydriatics for dilation of the pupil before phacoemulsification. Results: The preoperative pupil size was similar in intracameral lidocaine (2.90 ± 0.3 mm) and topical mydriatic (2.81 ± 0.4 mm) groups. Pupil dilation was slightly more in the topical mydriatic group (7.31 ± 1.0 mm) compared to the intracameral lidocaine group (6.96 ± 1.0 mm). The pupil size at the end of the surgery was nearly similar in both groups. Mean duration of the surgery was similar in both the groups. Both the groups had 27 patients who maintained dilation till the end of the surgery. The difference between the groups was not statistically significant and a post hoc power analysis showed the need for studies with a larger sample size. Conclusion: This study shows that injection of 0.2–0.3 ml of preservative-free lidocaine 1% intracamerally provides persistent, stable, satisfactory pupil dilation comparable to that of topical mydriatics, for safe phacoemulsification, and intraocular lens implantation. However, studies with a larger sample size are needed to confirm that both interventions perform similarly.
Keywords: Intracameral, lidocaine, mydriatic, pupil size
|How to cite this article:|
Shilpa Sunil K K, Latha N V. Comparative study of intracameral lidocaine and topical mydriatics in pupil dilation during phacoemulsification. Kerala J Ophthalmol 2021;33:311-5
|How to cite this URL:|
Shilpa Sunil K K, Latha N V. Comparative study of intracameral lidocaine and topical mydriatics in pupil dilation during phacoemulsification. Kerala J Ophthalmol [serial online] 2021 [cited 2022 Jan 19];33:311-5. Available from: http://www.kjophthal.com/text.asp?2021/33/3/311/331925
| Introduction|| |
Inadequate pupil dilation increases the risk of intraoperative complications in cataract surgery. Topical administration of anticholinergic or sympathomimetic agents are used to achieve pupil dilation for cataract surgery. However, there are several disadvantages with the use of topical eye drops for pupillary dilation. Topical eyedrops have slow and poor penetration through the cornea, which delays the onset of pupil dilation and lead to an increased waiting time before cataract surgery., Physiological and anatomic barriers result in absorption of <1% of the instilled mydriatic agents through the cornea and low bioavailability in the anterior chamber.,, The higher concentration of topical mydriatics needed to achieve adequate mydriasis may rarely cause systemic toxicity such as acute pulmonary edema and hypertensive crisis. Systemic toxicity is common in children and high-risk patients with uncontrolled hypertension or poor cardiac function.,, The effects of topical mydriatics may not sustain for the duration of surgery and lead to pupil constriction, especially in patients with intraoperative floppy iris syndrome and diabetes mellitus.
Intracameral injection of preservative-free lidocaine was attempted as an alternative to reduce the potential disadvantages of common mydriatics. Since anesthetic agents lack adrenergic or anticholinergic properties, these mydriatic and cycloplegic effects of intracameral lidocaine is due to a paralytic effect on the iris.
Cataract surgery is the most common ophthalmic surgical procedure performed in India. We designed a prospective study to compare pupil dilation and operative outcomes of conventional topical mydriatics and intracameral injection of lidocaine in persons undergoing cataract surgery by phacoemulsification at a tertiary care teaching eye care hospital in north Kerala.
| Methods|| |
The study protocol that used a prospective cohort design was approved by the institutional review board and ethics committee. Informed consent was obtained from all participants prior to enrolment in the study. The study was conducted from July 2018 to December 2019 at the Ophthalmology Department of the study institute. Patients with age-related cataract posted for cataract surgery, willing to follow the study protocol and provided informed consent were enrolled. Patients with ocular surface disorders, on immune suppressive therapy, diagnosed with collagen vascular diseases, previous refractive ocular surgeries and on chronic topical medications for any ocular condition, and diabetes mellitus were excluded from the study. Consecutive subjects were enrolled for the study after confirming eligibility.
Each subject had a detailed preoperative assessment that included uncorrected and best-corrected visual acuity, intraocular pressure and anterior chamber depth assessments, slit-lamp biomicroscopy assessment of the cornea and anterior segment, and posterior segment assessment. The lens was graded based on the LOCS III grading system. The operating surgeon allocated patients to one of the two intervention groups using a nonrandomized sequential alternate allocation approach. Masking of the operating surgeon was not possible as one of the intervention arms was the use of intracameral medication.
Intracameral lidocaine or topical mydriatics was used to dilate the pupil before cataract surgery by phacoemulsification and intraocular lens implantation. The topical mydriatic group received 1 drop of tropicacyl plus (tropicamide 0.8% and phenylephrine hydrochloride 5%) four times at 15 min interval in the Ophthalmology OutPatient Department starting 60 min before surgery. The intracameral lidocaine group was given preservative-free lidocaine 1% (0.2–0.3 mL) intracamerally after entry into the anterior chamber on the operating table. Epinephrine was not added to the irrigating solution. In both groups, the horizontal pupil diameter was measured before pupil dilation, after dilatation and at the end of surgery using the same caliper and by the same operator (LNV). All patients underwent cataract surgery by phacoemulsification by the same surgeon (LNV). The total surgical time and need for an additional mydriatic agent during the procedure were recorded.
The sample size for the study was estimated based on the estimates reported by Nikeghbali et al. The sample size for the study was estimated as 2 based on the reported standard deviations of 0.09 and 0.08 in the two groups and reported mean difference of 0.46 reported by Nikeghbali et al., 5% significance and 80% power. As the derived sample size was small, we decided to perform an observational study based on a convenience sample size of 30 to derive estimates from the local population that can be used to design the study.
The data were entered into an MS Excel spreadsheet and subsequently exported to SPSS software (IBM SPSS Statistics for Windows, v 22.0, Armonk, NY; IBM Corp) for statistical analysis. An independent t-test was used to compare the means of continuous variables and a Chi-square test was used to compare categorical variables. A P < 0.05 was considered statistically significant.
| Results|| |
The study included 30 patients in each group. The two groups did not differ by preoperative pupillary size and was 2.90 ± 0.3 mm in intracameral group and 2.81 ± 0.4 mm in topical mydriatic group [Table 1]. The distribution of preoperative visual acuity and IOP was similar in both the groups. The LOCS III classification showed that NO2-NO3+ variable amount of cortical cataract and posterior subcapsular cataract stage was the predominant type of cataract operated in both the groups.
The pupil dilated slightly more in the topical mydriatic group 7.31 ± 1.0 mm compared to the intracameral lidocaine group 6.96 ± 1.0 mm although this difference was not statistically significant [Table 1]. The pupil size at the end of the surgery were almost similar but slightly more for topical group (6.73 ± 1.0 mm) compared to intracameral lidocaine group (6.51 ± 1.4 mm) although the difference was not statistically significant [Table 1]. The mean difference, or in other words average change in pupil size was +4.5 mm in topical mydriatic group and +4.06 mm in intracameral lidocaine group. Thereafter, pupil size changed to −0.58 in topical mydriatic group and −0.45 mm in intracameral lidocaine group.
The duration of the surgery was same in both the groups 12.93 ± 1.23 min in intracameral lidocaine group and 12.90 ± 1.26 min in topical mydriatic group [Table 2]. Both groups had 27 patients who maintained dilation until the end of the surgery and 3 patients who didn't maintain dilation. Additional mydriatic was used in 1 patient in intracameral lidocaine group compared to 2 patients in topical mydriatic group. Intraoperative complications were seen among 2 patients in intracameral lidocaine group and 2 patients in topical mydriatic group. There were no postoperative complications in any patients. These differences did not show any statistical significance [Table 2]. Postoperative striate keratopathy was present in the first 2 patients in intracameral lidocaine group and was solved by injecting air bubble into anterior chamber before injecting preservative free lidocaine intracamerally for subsequent surgeries.
| Discussion|| |
Topical mydriatic agents have been routinely used to dilate pupils preoperatively in cataract surgery. It is commonly achieved by topical administration of anticholinergic (passive) and sympathomimetic (active) mydriatic agents. This regimen has many drawbacks. Slow penetration through cornea delays onset of mydriasis. Thus, the waiting time to operate is longer than the total operating time. There is limited bioavailability of topically administered substances and there is significant systemic absorption which leads to risk of cardiovascular side-effects, especially in patients with hypertension, cardiovascular diseases and in children. Another disadvantage is that mydriatic effect tends to wear off during surgery. The use of benzalkonium chloride as a preservative in topical eyedrops has led to side effects, mainly on the cornea (e.g., punctate epithelial erosion causing poor intraoperative surgical view). Therefore, alternative methods of pupil dilation have been assessed with the goal of decreasing the risk for unwanted local and systemic side effects.
The baseline characteristics of the study population in this study was consistent with previously reported studies.,,, The changes in pupil size in our study is consistent with previous studies,, comparing the effectiveness of topical mydriatics with that of intracameral lidocaine 1.0% alone or intracameral lidocaine 1.0% in combination with other mydriatic agents such as cyclopentolate 0.1% and phenylephrine 1.5%. These studies found that the use intracameral mydriatics alone produced prompt pupil dilation intraoperatively without the previous use of topical mydriatics. However, we found that the difference in pupil dilation or duration of surgery or time to dilation between intracameral and topical mydriatics was not statistically significant in this series.
Previous studies,, have reported that intracameral mydriatics produced adequate pupil dilation during cataract surgery. The potential advantages of intracameral mydriatics are multiple. First, omission of preoperative dilating eyedrops will ease the burden on the hospital staff. Moreover, the use of intracameral mydriatics in cataract surgery prevents the corneal side effects of intensive preoperative mydriatic agents. In addition, surgery can be scheduled using a staggered system to reduce the waiting time for patients. A study by Cionni et al. found that intracameral lidocaine 1.0% was effective in attaining good pupil dilation without the use of topical mydriatics preoperatively. The mydriatic effect of intracameral mydriatics did not wear off during the surgery, and the pupils were further dilated at the end of surgery. Sodhi PK et al. evaluated the use of intracameral lidocaine 1.0% to dilate the pupil in glaucoma filtering surgery intraoperatively and showed that intracameral lidocaine 1.0% can be used as a dilating agent in undilated eyes. A study by Nikeghbali et al. found that both intracameral lidocaine 1.0% and topical groups (cyclopentolate 1.0% and phenylephrine 5.0%) achieved significant pupil dilation in cataract surgery.
The sustenance of pupil dilation, use of additional mydriatics, and intraoperative complications were similar for both groups and consistent with previous reports.,,, In our study, the amount of pupil dilation was not significantly different during surgery, which lasted approximately 12 min. However, it is not clear how long the pupil dilation lasts after an intracameral lidocaine injection. We found pupil dilation in both the topical group and intracameral group to be similar as opposed to previous studies that reported a significant difference in pupil dilation between intracameral and topical mydriatics.,,,,,, It is possible that the lack of difference maybe a true population difference based on the characteristics of the iris. However, a post hoc power analysis showed that we did not have enough power (10.32%) to determine if this is a true lack of difference. A repeat estimation of the sample size based on the results of our study indicated the need for a much larger study to support the hypothesis that intracameral mydriatics have greater effectiveness than topical mydriatics in our population.
The current study highlights the importance of an appropriate sample size estimation and an understanding of the underlying assumptions that are used to determine sample size. The estimated sample size of 2, based on the previous study results, suggests an exceptionally large difference between the two interventions. Such a large difference between the interventions will make it unethical to withhold the better performing intervention, in this case, intracameral mydriatics to all patients. However, in clinical practice, we did not see such a huge difference between the two interventions. We decided to do an observational study as a cohort design before designing a randomized clinical trial to get better estimates of the sample size that may be needed for an adequate power (at least 80% power). The sample size, based on our initial results, was estimated as a minimum of 380 subjects if we design a noninferiority, randomized clinical trial.
Estimates of sample size are based on clinical assumptions and it is important to examine the underlying assumptions used. Sample size estimates for interventions are best derived from previous meta-analyses or clinical trials. In the absence of such studies, a prior study with a cohort design or a cross sectional study may be used. A pilot study is preferable if there are no prior estimates in the literature or if the estimated sample size seems implausible based on clinical experience.
| Conclusion|| |
Although our study shows that intracameral preservative free lidocaine provides persistent, stable, satisfactory pupil dilation , we recommend future studies from diverse settings to better understand the comparative effectiveness of intracameral mydriatics in our population and using a randomized clinical trial design. We recommend further studies from diverse settings to better understand the comparative effectiveness of intracameral mydriatics in our population and using a randomized clinical trial design.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2]