Study of safety and efficacy of sub-Tenon and subconjunctival anesthesia in manual small-incision cataract surgery for hard-grade cataracts

Abstract

PURPOSE:

The purpose was to study the safety and efficacy of sub-Tenon and subconjunctival anesthesia in manual small-incision cataract surgery (MSICS) in patients with hard-grade cataracts.

STUDY DESIGN:

The design of the study was a prospective, observational, and randomized control study.

MATERIALS AND METHODS:

A total of 196 eyes, including 98 eyes in the subconjunctival anesthesia group (group A) and 98 eyes in the sub-Tenon anesthesia group (Group B), undergoing MSICS were enrolled in the study. A single surgeon performed all the surgeries. Intraoperative and postoperative pain scores, patient comfort, surgeon’s satisfaction, and intraoperative complications were examined.

RESULTS:

The mean age of patients in Group A was 66.64 ± 9.95 years and that of patients in Group B was 64.52 ± 9.46. No statistically significant difference was noted in the intraoperative (P = 0.54) and postoperative pain (P = 0.66) scores between the two groups. There was no pain (0 score) in 30% of patients in Group A and 35% of patients in Group B intraoperatively. The average surgical time (P = 0.66) and surgeon’s comfort (P = 0.34) were not statistically significant. The mean corneal haze was 0.054 ± 0.12 in group A and 0.065 ± 0.22 in group B (P = 0.45). Two patients in group A required supplemental anesthesia. There were no surgical complications that could compromise visual outcomes. No patients in either group showed alterations in vital parameters or required intravenous sedation.

CONCLUSION:

Both techniques of anesthesia are safe and effective for performing MSICS in hard-grade cataracts. However, it is prudent to choose a technique according to the surgeon’s requirements.

Introduction

Cataract surgery is the most common surgical procedure in ophthalmology and is known to be the most cost-effective of all surgical procedures.[1] Moreover, cataract surgery has been reported to have a good safety profile.[1,2] Quick recovery of visual function and ease of administration make topical anesthesia popular among ophthalmologists. Various forms of topical anesthesia have been employed for cataract surgery, which include topical proparacaine hydrochloride drops, 2% lignocaine jelly, and intracameral 1% lignocaine hydrochloride along with topical proparacaine hydrochloride drops.[3,4,5]

The global trend for anesthesia during cataract surgery has shifted from general anesthesia, sedation, and hospitalization to regional ophthalmic block (ciliary ganglion, ophthalmic, oculomotor, abducent, and trochlear nerves) as well as topical anesthesia with daycare management owing to the advancements in cataract surgery techniques. This improvement is predicated on reduced surgical wound size and self-sealing architecture as well as better intraocular lens design, less tissue manipulation, and modern instrumentation.[1,6] The choice of the regional block varies from retrobulbar or peribulbar block to sub-Tenon, subconjunctival, intracameral, and topical anesthesia or a combination of any of these blocks.[4] Retrobulbar and peribulbar anesthesia are associated with globe perforation, retrobulbar hemorrhage, optic nerve injury, brain-stem anesthesia, and other serious complications.[7,8,9]

However, sub-Tenon block provides excellent anesthesia and akinesia without requiring a sharp needle. This method is particularly appropriate for patients at a high risk of complications from sharp needle blocks; for example, high myopes, patients with scleral explants, and those taking anticoagulants. This technique decreases the incidence of patient anxiety and painful experience associated with the use of needles in the peribulbar block.[10] Subconjunctival anesthesia is useful for cataract, pterygium, and superficial glaucoma surgeries.

The present study prospectively compared the effectiveness and safety of sub-Tenon and subconjunctival anesthesia in manual small incision cataract surgery (MSICS).

Materials and Methods

Sample size

The sample size was calculated as 98 eyes in each group, considering the failure rate of 0.235 from prior data and type 1 error probability of 0.05.

Patient selection and study design

Approval for the study was obtained from the Ethical Committee of the hospital. Written informed consent was obtained from each participant. The study adhered to the tenets of the Declaration of Helsinki. The study duration was 18 months (October 2020–April 2022). This prospective, comparative, randomized, and interventional study comprised 196 eyes. Patients with senile cataracts of nuclear opalescence grades 4 and 5 according to the LOCS-III classification who visited the outpatient department of our tertiary care center and were willing to undergo surgery were included in the study. Patients with allergies to the topical anesthetics used, nystagmus, deafness, barrier to communication, extreme anxiety, neurological disorders, complicated and subluxated cataracts, nondilating pupil, those who were unable to understand the Visual Analog Scale (VAS), and one-eyed patients were excluded from the study.

Preoperative assessment included best-corrected visual acuity, slit-lamp examination, intraocular pressure check with a handheld tonometer, retinal evaluation, A-scan biometry for axial length measurement, and intraocular lens power calculation. Morphologically, cataract grade was evaluated based on the LOCS-III classification using a slit lamp.

The patients were randomized into subconjunctival and sub-Tenon anesthesia groups using simple random sampling. In total, 196 eyes were numbered and randomized into two groups using the software available at https://www.randomizer.org. Group A included 98 patients undergoing MSICS under subconjunctival anesthesia, and Group B included an equal number of patients undergoing MSICS under sub-Tenon anesthesia. Proparacaine hydrochloride drops (Paracain 0.5%, Sunways Pvt. Ltd., India) were instilled in the lower fornix three times at an interval of 5 min before the start of the sub-Tenon and subconjunctival anesthesia in both groups. In Group A patients, 0.5 cc of 2% xylocaine (Xylocaine, AstraZeneca Ltd., India) was injected into the lower and upper bulbar conjunctivas after lifting them with tooth forceps. In Group B patients, a lid speculum was applied. A conjunctiva and Tenon’s capsule were picked up with the help of tooth forceps. The site selected for the block was the inferonasal quadrant 7–10 mm away from the limbus. After making a small cut, the sub-Tenon’s space was assessed with closed, blunt, curved Westcott scissors to create a thin channel just past the equator of the globe to the Tenon’s space. A blunt-tipped cannula was then inserted into the sub-Tenon’s space. Subsequently, 4 cc of 2% lignocaine hydrochloride was injected into the space. The lid speculum was removed, and gentle digital pressure was applied over the closed lids with two fingers for 2–3 min. Preoperatively, the pupils were dilated with topical phenylephrine 5% and tropicamide 0.8% drops (Appamide, Appasamy Ocular Devices, Puducherry, India) instilled thrice every 15 min. No nonsteroidal anti-inflammatory drugs were used preoperatively. None of the patients received preoperative or intraoperative sedation.

The patients were asked to inform about pain or discomfort experienced while instilling anesthesia, during the procedure, and postoperatively up to 4 h. The patient’s subjective perception of pain was graded into none, mild, moderate, and severe. Eyeball movement during the surgery was graded as none, slight, moderate, and excessive. The surgeon’s satisfaction was graded as dissatisfied, somewhat satisfied, and satisfied, and the patient’s satisfaction was graded as dissatisfied and satisfied. Complications related to anesthesia were observed.

Surgical technique

A single surgeon performed all the surgeries. All patients were operated on from the superior side. A universal eye speculum was used in all cases. The patients were instructed to fixate on the microscope light during the surgery. Conjunctival peritomy was performed using conjunctival scissors after holding the conjunctiva with Hoskins forceps. A straight scleral incision of approximately 6.5 mm was created with a 15 no. blade 1.5 mm away from the limbus superiorly. A 20 G side port incision was created on the appropriate side, as required. Trypan blue dye was injected for the staining of the anterior capsule. Excess dye was washed out with a balanced salt solution (BSS). An ocular viscoelastic device was injected through the side port with a 23-G blunt tip cannula. Continuous curvilinear capsulorhexis (CCC) was completed using a 26-G bent needle mounted on a 2 cc syringe. The size of the CCC in both groups was maintained at approximately 5.0–5.5 mm. The sclerocorneal tunnel was opened with a 2.8 mm keratome. Hydrodissection was performed with BSS. The nucleus was brought into the anterior chamber, and viscoexpression of the nucleus was done. A thorough cortical cleanup was accomplished using Simcoe’s cannula. The anterior chamber was filled with viscoelastic. A 6-mm rigid PMMA monofocal IOL was implanted in the capsular bag. Stromal hydration of the side port was achieved. Viscoelastic was washed from the anterior chamber and the anterior chamber was formed with BSS, and the wound was secured. In case of wound leakage, a 10-0 nylon suture was placed at the sclerocorneal junction. Subconjunctival injection of steroids and antibiotics was avoided. If the patient complained of pain during the surgery, supplementation of proparacaine hydrochloride drops or subconjunctival injection of lignocaine or peribulbar block or repeat sub-Tenon’s block was given.

After completion of the procedure, the patients were taken to the recovery room. A standard 10-point VAS was used to assess intraoperative and postoperative pain. Postoperative pain was assessed 30 min after the completion of the surgery. A senior resident unaware of the study objectives performed the pain-grading procedure. The operating surgeon was not present during the assessment of the pain score. The patient was also asked whether they would be opting for a similar anesthetic technique for the fellow eye cataract surgery if the other eye was due for cataract surgery.

The surgeon’s subjective impression of corneal haze (grade 0 = clear, 1 = mild haze, 2 = moderate haze, and 3 = severe haze), discomfort during the surgery (grade 0 = no pain, 1 = mild pain, 2 = moderate pain, and 3 = severe pain), complications, and supplemental anesthesia were recorded.

Furthermore, the anesthetist noted the vital parameters, such as blood pressure, pulse rate, and oxygen saturation, intraoperatively and the need for supplemental intravenous sedation.

Statistical analysis

The data were entered into an Excel spreadsheet (Software version 14.1.0 [110310]/2011) (Microsoft Corporation, Redmond, WA, USA), and statistical analysis was performed with SPSS version 13.0 (SPSS Inc., Chicago, IL, USA). Intraoperative and postoperative pain and operating conditions were assessed using the Wilcoxon (Mann–Whitney) rank-sum test. Dichotomous comparisons were performed using Fisher’s exact test. P < 0.05 was considered statistically significant. An unpaired t-test was performed to determine the statistical significance between continuous features of two separate groups. The statistical significance of the categorical variables of two separate groups was tested using the Chi-square test. The critical value taken for hypothesis testing was 0.05. Statistical significance was considered if P < 0.05.

Results

A total of 196 eyes from 196 patients were enrolled in the study. The study included two groups: Group A comprised 98 eyes that had undergone MSICS under subconjunctival anesthesia and Group B comprised 98 eyes that had undergone MSICS under sub-Tenon anesthesia. The mean age of patients in Group A was 66.64 ± 9.95 years and that of patients in Group B was 64.52 ± 9.46 years. Group A included 54 men and 44 women, whereas Group B included 52 men and 46 women. Forty-eight eyes in both groups had nuclear opalescence grade 5. Demographic details of the patients are furnished in Table 1.

Table 1.

Demographic details of the group studied

Parameters		Group A (n=98)		Group B (n=98)		P
Age (years)		66.64±9.95		64.52±9.46		0.06
Male		54		52		0.77
Female		44		46		0.77
Eye
Right eye		70		74		0.51
Left eye		28		24		0.51
Grade of cataract
NO 4		40		41		0.56
NO 5		58		57

NO: Nuclear opalescence

The average pain score on the VAS during the administration of anesthesia was 0.675 ± 1.02 (range 0–5) in Group A and 0.982 ± 1.22 in Group B (P = 0.23). Zero scores were reported in 40% of patients in Group A and 43% in Group B.

The intraoperative pain score was 0.926 ± 1.234 (range 0–8) in Group A and 0.746 ± 1.335 (range 0–7) in Group B (P = 0.54). Zero scores were reported in 30% of patients in Group A and 35% in Group B.

The mean postoperative pain score was 4.784 ± 1.054 (range 0–8) in Group A and 3.321 ± 1.222 (range 0–6) in Group B (P = 0.66). Zero scores were reported in 20% of patients in Group A and 34% of patients in Group B.

The average surgical time was 10.45 ± 2.34 min in Group A and 9.47 ± 3.33 min in Group B (P = 0.66).

The mean corneal haze was 0.054 ± 0.12 in Group A and 0.065 ± 0.22 in Group B (P = 0.45). The average surgeon’s comfort score was 0.34 ± 0.31 in Group A and 0.23 ± 0.23 in Group B (P = 0.34).

Two patients (2%) in Group A required supplemental anesthesia in the form of repeat subconjunctival anesthesia in one and peribulbar anesthesia in the other patient. None of the patients in Group B required supplemental anesthesia, and there were no surgical complications that could compromise the visual outcome.

In Group A, 50 (51%) patients had bilateral cataracts and 47 (48%) patients were willing to consider the same technique for the other eye cataract surgery. In Group B, 47 (48%) patients had bilateral cataracts and 40 (41%) patients were willing to consider a similar technique for the other eye. In both groups, two patients wanted another anesthesia technique for cataract surgery.

The average blood pressure was systolic 120 ± 4 mm Hg and diastolic 80 ± 2 mm Hg in both groups collectively. The mean pulse rate was 80 ± 2, and oxygen saturation was maintained at 97%–99% in both groups. None of the patients in either group required intravenous sedation.

Discussion

Cataract surgery is the most commonly performed eye surgery, and the peribulbar and retrobulbar technique for the administration of anesthesia is routinely used. With the advancements in cataract surgery techniques, anesthesia techniques have also evolved. Topical anesthesia has become popular in cataract surgery. However, MSICS involves the handling of the conjunctiva, sclera, and iris during the procedure, which is painful. Therefore, peribulbar and retrobulbar anesthesia form the main common mode of anesthesia practice. There have been studies on the safety and efficacy of various anesthetic techniques in MSICS.[4,5,11,12,13] However, either all grades of cataracts or grade 1–3 were selected in these studies. Hard-grade cataracts constitute a significant proportion of the workload in developing countries owing to the late presentation of patients for surgery.[14,15,16] MSICS forms a major chunk of cataract surgery in the developing world. Studies on MSICS under subconjunctival and sub-Tenon anesthesia in hard-grade cataracts in nuclear opalescence of grades 4 and 5 are lacking. Therefore, the present study was undertaken.

This study showed that both subconjunctival and sub-Tenon anesthesia are comparable in terms of the safety of the procedure and the comfort of the surgeons and patients in those with nuclear cataracts of grades 4 and 5. Furthermore, there was no significant difference between the two groups during the administration and in intraoperative pain scores. The average pain score on the VAS during the administration of anesthesia was 0.675 ± 1.02 (range 0–5) in Group A and 0.982 ± 1.22 in Group B (P = 0.23). Zero scores were reported in 40% of patients in Group A and 43% in Group B. In their study on anterior subconjunctival and sub-Tenon anesthesia in all grades of cataracts, Ajay et al. mentioned that none of the patients experienced pain during the administration of anesthesia.[11] Wu and Tang showed that 97% (58/60) had no pain during the procedure.[17] Antony et al. and Ashok et al., in their study on the comparison of sub-Tenon with peribulbar anesthesia in MSICS, reported that a significant number of patients felt pain during the administration of peribulbar anesthesia.[18,19] Conjunctival anesthesia is important before performing subconjunctival and sub-Tenon injections. Instillation of proparacaine hydrochloride drops three times before the start of the injection helps in reducing the pain.

The intraoperative pain score was 0.926 ± 1.234 (range 0–8) in Group A and 0.746 ± 1.335 (range 0–7) in Group B (P = 0.54). Zero scores were reported in 30% of patients in Group A and 35% in Group B. A similar observation was made by Gupta et al. and Antony et al. in their study on the use of intracameral lignocaine. A mean pain score of 0.70 (SD ± 0.97) was obtained, which is comparable to that obtained in the sub-Tenon group of our study.[4,18] The perception of pain may differ from person to person, which also depends on tolerance and personal traits.

The mean postoperative pain score (Group A: 4.784 ± 1.054; Group B: 3.321 ± 1.222; P = 0.66) and surgeon’s comfort while performing the procedure were similar in both groups. The safety and efficacy of the anesthetic procedures were proven by the observation that the surgeon’s comfort level and average surgical time were almost the same in both groups (10.45 ± 2.34 min in Group A and 9.47 ± 3.33 min in Group B, P = 0.66). The anesthesia administration and surgery were performed by the same surgeon to avoid bias related to the anesthesia technique and the surgical procedure. None of the patients experienced visually significant intraoperative surgical complications or corneal haze. Two patients (2%) in Group A required supplemental anesthesia in the form of repeat subconjunctival anesthesia in one and peribulbar anesthesia in the other. One patient felt mild pain while maneuvering the nucleus in the bag, for which repeat subconjunctival 1 cc of lignocaine was administered. Another patient had a deep-set socket, for which a peribulbar block was given. The reason could be the lower volume of subconjunctival lignocaine (2 cc) in Group A.

The preference for the same anesthesia technique for the other eye cataract surgery was higher in the subconjunctival group (48%) than in the sub-Tenon group (41%). In both groups, two patients wanted another anesthesia technique for cataract surgery. Joshi, in his study on single-drop proparacaine hydrochloride (89.11%) versus additional intracameral lignocaine (90.18%) for phacoemulsification in age-related cataract surgery, reported that an almost equal number of patients preferred the same anesthetic technique.[3]

The average blood pressure was systolic 120 ± 4 mm Hg and diastolic 80 ± 2 mm Hg in both groups collectively. The mean pulse rate was 80 ± 2, and oxygen saturation was maintained at 97%–99% in both groups. None of the patients in either group required intravenous sedation. This finding is comparable to that from a study by Joshi on age-related cataracts and patients with comorbid conditions scheduled for cataract surgery with phacoemulsification.[3,20]

Nonetheless, the surgeon’s expertise and experience are of prime concern while performing MSICS under minimal anesthesia. This study has its own limitations. The volumes of anesthetic agents used in both techniques were different. The study involved a single surgeon and a single center. The inclusion of two or more centers and surgeons with different expertise may strengthen the conclusions of this study. The strength of the study was the systematic analysis of two anesthesia techniques in hard-grade cataracts.

Conclusion

The subconjunctival and sub-Tenon techniques are safe and effective for performing MSICS in hard-grade cataracts. The pain experienced by the patients and the surgeon’s comfort were comparable in both groups. The ease of application and adequate effect to complete the surgery make these techniques viable alternatives for hard cataracts. However, it is prudent to individualize the anesthetic technique according to the patient’s and surgeon’s needs.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.