The adult corneal endothelial density is from 1500 to 2500 cells/mm3 with a total number of about 3,00,000 to 5,00,000. There is great individual variation in cell counts.^[1] Loss or damage of endothelial cells leads to an increase in corneal thickness, which may ultimately induce corneal decompensation and loss of vision.^[2]

Peribulbar anesthesia was introduced in 1986 as an effective and safe alternative method to retrobulbar anesthesia. Despite the increased safety, a few serious complications have been reported: perforation of the globe, retrobulbar hemorrhage, injury of the optic nerve, retinal artery or vein occlusion, eye movement disturbances, and intravascular injection. Threat of these complications along with the introduction of the self-sealing tunnel technique led to a rediscovery of topical anesthesia.^[3] The major advantages of topical anesthesia in cataract surgery include no painful injection through the skin or conjunctiva, avoidance of the risks and complications of peribulbar and retrobulbar injections, preserved ocular motility during surgery, and immediate visual rehabilitation after surgery. Nevertheless, some authors advise caution with the use of topical agents because of their possible toxic secondary effects on intraocular structures, in particular damage to the corneal endothelium. Changes in the ultrastructure of corneal endothelial cells and an increase in polymorphism and cellular edema have been reported.^[4] While there is akinesia of the eyelids and the eyeball during peribulbar block, the eyelids and eyeball are not static during topical anesthesia, so this difference alters the surgical manipulation and hence may affect the endothelial cell loss during surgery. To the best of my knowledge there are not many studies that have compared endothelial cell damage in cataract surgeries using peribulbar anesthesia and topical anesthesia. Thus, in view of these perspectives this study was planned to find out the amount of endothelial cell damaged during cataract surgery by phacoemulsification, comprising peribulbar anesthesia and topical anesthesia.

Study design, settings and participants:

It was a hospital based prospective study conducted over a period of one year in department of ophthalmology of a tertiary care teaching hospital of Northern India. All Patients undergoing phacoemulsification with intraocular lens implantation were divided into two groups with 55 patients in each group. Group I patients underwent phacoemulsification under peribulbar anesthesia (2 percent lignocaine + adrenaline 2%) and group II under topical anesthesia (0.5 percent proparacaine or lidocaine 2 percent jelly).Patients with previous corneal disease, corneal trauma, or intraocular surgery, glaucoma or uveitis, diabetes mellitus, pseudoexfoliation syndrome, endothelial cell count less than 2000 cells/ mm², anterior chamber depth less than 2mm, Hyper mature cataract, intra operative complications – PCR, Vitreous loss, total surgical time >15 mins and those who use contact lenses were excluded from the study.

Methodology

The patients were selected by block randomization by making blocks of four and generating a computer based random sequence within each block irrespective of their sex and place of residence in Himachal Pradesh. These cases were preoperatively examined clinically and informed consent was taken. Preoperative examination included: visual acuity using Snellen chart, refraction by streak retinoscopy and autorefractometer, complete anterior segment examination using slit Lamp Biomicroscopy, Intraocular pressure measurement using Goldmann’s applanation tonometer, fundus examination using direct and indirect ophthalmoscopy, keratometry and endothelial cell count measurement.

Corneal endothelial cell count measurement - The endothelial cell count was performed using Topcon Specular Microscope Model SP 1P, a noncontact device that photographs the endothelium. For the examination, the patient was seated at the appropriate height with his or her chin resting on the chin rest of the instrument. Light beam of specular photomicroscope passes through the cornea & it encounters series of interfaces between optically distinct regions. Some light is specularly reflected back to the photomicroscope and forms an image which is captured. The endothelial cells are counted by automated counting of cells by the software of specular microscope. Panorama mode was selected as this function takes 3 images in different areas central, nasal and temporal and automatically combines them creating a larger area for observation and analysis of endothelial cells.

Preoperative preparation:

Topical antibiotic drops (Moxifloxacin-0.5%) was instilled every six hours for 24 hours before surgery, in the eye to be operated. Xylocaine (2%) sensitivity was done.

Preparation of eye to be operated was done by trimming the eyelashes on the night before surgery. Patient was given Tab. Alprazolam 0.25 mg on the night before surgery. Pupil of the eye to be operated was dilated by using Tropicamide (0.8%) + Phenylephrine (5%), Cyclopentolate (1%) and Ketorolac tromethamine 0.5%. These drops were instilled four times over one hour to maintain mydriasis during surgery.

Anaesthesia

The patients were divided into two groups

Group I - Peribulbar Anesthesia group: A solution containing 2 percent lignocaine, adrenaline 2% and hyaluronidase was used. This was prepared by taking 1 ml of lignocaine and was mixed with 1500 IU hyaluronidase, this was added to 29 ml of 2 percent lignocaine with adrenaline. Superior & inferior injections of 5 ml each were given with a 25 G 1-inch needle. The patient was instructed to look straight ahead in the primary gaze position. Inferior injection was given at the junction of the outer one third & inner two third of the lower orbital rim. Superior injection was given usually nasally just above the medial canthus

Group II - Topical Anesthesia: Local anesthetic eye drops of 0.5 percent proparacaine or lidocaine 2 percent jelly was used. The drops were instilled once before the surgery started.

Phacoemulsification: All operations were performed by the same surgeon and comprised phacoemulsification with the peristaltic and implantation of a poly (methyl methacrylate) posterior chamber IOL in the capsular bag.

Bandage was removed on the first day after operation. Topical antibiotic with steroid combination (Moxifloxacin 0.5% + Prednisolone 1%) given from 1st POD for 6 times per day till 2 weeks then tapered off slowly with 4 times and 2 times daily over 2 weeks period respectively. Topical cycloplegics were given wherever required. Patients were followed up at 1st postoperative day (POD), 1 week, 6 weeks after cataract surgery.

Statistical analysis

Data were analyzed and statistically evaluated using SPSS software, version 25 (Chicago II, USA). Quantitative data was expressed in mean, standard deviation and difference between pre-post was tested by paired t test while difference between mean of two group were tested by student t test or Mann Whitney U test. Qualitative data were expressed in percentage and statistical differences between the proportions were tested by chi square test. ‘p’ value less than 0.05 was considered statistically significant.

Ethical issues

All participants were explained about the purpose of the study. Confidentiality was assured to them along with informed written consent. The study was approved by the Institutional Ethical Committee.

Both the groups were comparable in term of baseline characteristics. Preoperative visual acuity was divided into three categories: 6/12 to 6/24 P, 6/36 – 6/60 P and worse than 6/60P. Group I patients in each category were 14.5%, 38.2%, 47.3% respectively. Group II patients in each category were 21.8%, 43.6%, 34.5% respectively. Type of cataract are also depicted in table 1. The mean endothelial cell counts preoperatively in Group I was 2785.49 ±339.08, at 1st POD was 2718.98 ± 322.12, at 1st postoperative week was 2641.44 ±320.11, at 6th postoperative week was 2561.62 ±318.61. The mean endothelial cell count in Group II preoperatively was 2854.09 ±235.51, at 1st POD was 2752.11± 221.10, at 1st postoperative week was 2605.42 ± 235.98 and at 6th postoperative week was 2515.71 ± 243.57. Mean central corneal thickness was also comparable between both groups at all time period (table 2). The mean endothelial cell loss at 6 weeks postoperatively was 7.98±3.91% in group I and 11.94±3.75% in group II.

Table 1: Baseline characteristics between both groups

Table 2: Comparison of endothelial cell count and central corneal thickness at different interval between both groups

The use of topical anesthesia rather than peribulbar or retrobulbar anesthesia in cataract surgery is becoming increasingly popular. Topical anesthesia by subconjunctivally injected anesthetic agents in combination with the sponge technique, instillation of lidocaine gel, or anesthetic eyedrops alone have been described. ^[5,6] Pure topical anesthesia with anesthetic eyedrops had a pain-killing effect as good as peribulbar anesthesia. The use of topical anesthesia in modern cataract surgery became feasible after the development of small suture less incisions made through clear cornea or at the limbus. Strategic selection of the cataract incision site, combined with topical anaesthesia, results in a minimally invasive procedure with quick visual recovery and high patient satisfaction without the drawbacks of postoperative diplopia, ptosis, periocular ecchymosis, subconjunctival haemorrhage, and chemosis. However, the significant drawback of this technique lies in its failure to provide adequate motor and sensory anaesthesia. This leads to an increased risk for intraoperative complications due to unrestricted eye movements and insufficient pain control. Endothelial toxicity may be caused by topically applied anesthetic agents when a trans corneal portal of entry is present. ^[7-9]

In view of these perspectives, present study was designed to compare the endothelial cell loss between peribulbar anaesthesia and topical anaesthesia following uncomplicated phacoemulsification with posterior chamber intra ocular lens.

The effect of type of anaesthesia on the endothelium was evaluated by calculating the endothelial cell loss. The mean endothelial cells were comparable in both the groups at all time period. There was a statistically significant (p <0.01) decrease in endothelial cell count in both the groups from baseline, at all follow-up period. The mean endothelial cell loss at 6 weeks postoperatively patients who received peribulbar anaesthesia was 7.98±3.91% and patients who received topical anaesthesia was 11.94±3.75%. Endothelial cell loss could be as high as 20.62 ±13.63% as was reported in a study by Choi JY et al^[10] who investigated the extent of long-term corneal endothelial loss after uneventful cataract surgery and 10-year endothelial cell loss rate. A similar study was conducted by Heuermann T et al^[4] (2002) in which endothelial cell loss was 11.11% in the peribulbar group and 12.55% in the topical/lidocaine group. However, endothelial cell loss was not found to be statistically significant in their study. In our study the possible reason for the lesser endothelial cell loss in peribulbar group is due to the akinesia of the globe and the eyelids and endothelial toxicity of the topical anesthetic agents are avoided. Pain and discomfort complained by some of the patients operated under topical anaesthesia might affect the perfection of some of the steps during surgery.

The mean central corneal thickness was comparable in both groups at various times. Patients in both the groups attained central corneal thickness almost equivalent to their preoperative range by the end of 6 weeks. The mean central corneal thickness increased in both the groups at 1st POD which could be due to the transient endothelial dysfunction and endothelial cell loss which tends to recover by the 1st postoperative week. Sachin M. Salvi et al^[11] evaluated changes occurring in central corneal thickness after phacoemulsification, the central corneal thickness reduced to preoperative levels by the 1-week postoperative period. Ventura AC et al^[2] (2001) also concluded that preoperative values of central corneal thickness were restored by 3 and 12 months, even though significant endothelial cell losses had occurred. No correlation existed between central corneal thickness and central corneal endothelial cell numerical density. Our findings were also similar to these studies.

The proponents of topical anaesthesia administration may justify its use due to the side effects of peribulbar anaesthesia such as perforation of the globe, retrobulbar haemorrhage, injury of the optic nerve, retinal artery or vein occlusion, eye movement disturbances, and intravascular injection, which are potentially sight threatening, globe threatening and life-threatening complications. Topical anesthesia greatly reduces the risk of these complications and eliminates those stemming from the needle and systemic toxicity. Yet, concerns still exist including those related to incomplete akinesia and patient discomfort. Surgery is more difficult in cases of increased motion, especially in uncooperative patients. Squeezing and eye movement could be found significantly less frequently after peribulbar anesthesia. ^[7,12]

Limitation:

The person performing the postoperative examinations was not masked to the anesthesia technique used, which may have introduced bias. This could have been prevented by using an observer masked to the technique.

Based on finding of our study it can be concluded that peribulbar anaesthesia was better as compared to topical anaesthesia when the endothelial cell loss was taken into consideration. Further study with larger sample size was needed with long term follow up to see complete effect of both anesthesia.

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