A comparative study of divide and conquer, stop and chop and direct chop techniques of nucleotomy in topical phacoemulsification:
 an interventional study

Introduction

When the lens of the eye becomes opaque, it develops a condition known as a cataract, which can cause blurriness, colour changes, haloes around lights, and at its worst, blindness. Senile cataracts, in which the lens gets obscured owing to ageing, are the most common kind of cataract, despite the fact that there are a number of probable causes and risk factors for their formation.¹ The term “senile” (age-related) cataract is used to describe the condition in around 90% of cataract patients. Here, the lens’ consistent clouding is a result of ageing. Light is directed on the retina via the lens, which is located in the posterior part on the eye, to create sharp images. This makes it possible to see near as well as distant objects. Cataracts alter this ablility of the lens.¹ We incur an increased risk of acquiring cataracts as we age. Diabetes, UV exposure, and genetics are potential risk factors. Unfortunately, there is no known treatment for preventing cataracts from developing.² Surgery is the only treatment that can successfully remove a cataract.³ From more traditional methods like Cataract Couching and Intracapsular Cataract Extraction (ICCE) to more modern techniques like Conventional ECCE and SICS, cataract surgery has experienced tremendous developments throughout the years.

Phacoemulsification, a variation of ECCE that Charles Kelman first presented in 1967 and which rose to prominence in the 1980s, is one of the more recent techniques. This sutureless procedure uses an ultrasonic handpiece with a titanium needle and a piezo electric crystal. To emulsify the nucleus, the needle vibrates at a speed of 4000/second. The nucleotomy approaches of Divide & Conquer, Stop & Chop, Direct chop are widely used for phacoemulsification. Using the “Divide & Conquer” approach, the nucleus is split in 4 quadrants and trenched. Next, each quadrant is emulsified and aspirated individually. The Stop & Chop approach comprises of constructing a crater to enable partial nucleus removal, and then cutting. During Direct chop or Phaco chop, the phaco probe is surgically inserted in the lens nucleus, later breaking down of the nucleus using a chopper. Bimanual irrigation and aspiration are utilised after nucleus therapy to remove the epinucleus and cortical tissue. A PCIOL is then inserted into the capsular bag.⁴

One of the most prevalent forms of corneal endothelium damage is surgery within the eye. Mechanical damage caused by anterior chamber manipulation because of a hard cataract, increased vibration and heat generated by the phaco tip have all been associated with endothelial injury during phacoemulsification.⁵ Early studies found that phacoemulsification or a related procedure for removing cataracts produced a greater loss of endothelial cells (30-40%) than more standard extraction methods. However, with the use of new technology and viscoelastic materials, this has substantially reduced.⁵ The lattice structure of collagen fibrils has been ascribed to the capacity of the human cornea to transmit light, additionally state of dehydration maintained at the endothelium level by a number of corneal endothelial pumps, tight cell junctions as well as chemical modulators, which reduces scattering of light at the level of corneal stroma in conjunction with corneal protein known as crystallin.⁶ A specular microscope is a type of microscope that employs optical reflection. It shines light onto the cornea and records the picture that reflects off the optical contact between the endothelium of the cornea and the aqueous humour.⁷ The corneal endothelium is comprised up of hexagonal cells assembled in a semi-regular configuration. Morphologic analysis can be performed before surgery on individuals with suspected endothelial dystrophies or a history of repeated operations. Endothelial loss raises mean cell area while decreasing mean cell density. Depending on the level of Corneal Endothelial decompensation and the extent of corneal edema, quantitative indicators like Hexagonality, Coefficient of variation and cell area with standard deviation become aberrant.⁶

Protocol

This study takes place in a hospital and involves patients with cataracts who visit the Ophthalmology OPD at AVBRH, Sawangi (Meghe), Wardha and agree to undergo Topical Phacoemulsification surgery. The study follows inclusion and exclusion criteria, and has received approval from the Institutional Ethics Committee of Datta Meghe Institute Of Higher Education And Research (DMIHER (DU)/IEC/2023/1035, 01/05/2023). Around 114 patients are scheduled to undergo topical phacoemulsification using three different nucleotomy techniques. These patients will undergo specular microscopy examination to assess their corneal endothelial cell count and central corneal thickness. Before participating in the study, the participants will undergo a screening process to ensure they meet the criteria for inclusion. In this three arm parallel interventional study patients will be divided in three groups randomly:

The patients will be examined after one day post operatively and will be followed up after 4 weeks.

Inclusion criteria

Patients >50 years of age with grade 1-3 Immature Senile Cataract.

Exclusion criteria

Outcomes

Our study focuses on determining the surgical technique that results in minimal corneal endothelial cell loss and maximum improvement in post-operative visual acuity for patients. These depend upon intra operative variables like Ultrasound time, Use of balanced salt solution.

When it comes to surgical techniques, the direct chop method of nucleotomy requires less ultrasound time and the use of balanced salt solution compared to the other two techniques. This suggests that patients who undergo direct chop nucleotomy may experience better outcomes.

Research done by Park J et al. found that using Direct chop approach resulted in decreased Ultrasound time and decreased use of balanced salt solution as opposed to the Divide & Conquer and Stop & Chop approach for patients with nuclear sclerosis grade 4 cataract. Additionally, two months after cataract surgery, the direct chop group had a significantly lower Corneal endothelial cell loss compared to the Divide & Conquer and Stop & Chop groups in the same nuclear sclerosis grade 4 cataract group.¹⁰

The direct chop technique may prove to be a more efficient method for removing lenses, while minimizing corneal endothelial decompensation, compared to the Divide & Conquer and Stop & Chop approaches.¹⁰

The technique of Phaco chop has gained immense popularity over divide-and-conquer, due to its numerous advantages, as evidenced in a study conducted by Moore et al. Despite its challenging nature, Phaco chop utilizes the natural cleavage planes within the nucleus, resulting in minimal energy used to break it into smaller fragments. The Following advantages were seen

Research done by Wong et al. found that Direct Chop technique had significant advantages than Divide & Conquer method in terms of Ultrasound power and duration. Additionally, the Direct chop approach needed less surgical time and intraoperative manipulation intraocularly, with no discernible increase in complications during or after surgery.¹²

These studies are in favour of our expected outcome.

According to Kaur et al., all 3 approaches of Phacoemulsification (Divide & Conquer, Stop & Chop and Direct Chop) are uniformly successful. The amount of Central Corneal Thickness alterations & Corneal Endothelial Cell loss in all 3 procedures is virtually identical when performed by an experienced surgeon.⁵

Analysis

Descriptive statistics will be used to tabulate and characterise the results over the outcome variables; The mean and standard deviation of the data over the outcome variables will be checked for normal distribution. The interquartile range (IQR) and skewed distributions may be found using median statistics. For descriptive statistics, categorical and binary variable frequencies and percentages will be tallied. Every statistical study will be performed using R-software free version. The analysis of the inferential statistics will follow the guidelines provided below.

Outcome: The three groups will be compared using inferential statistics to determine the measurement score that was obtained (A-Stop & Chop, B-Divide & Conquer C-Direct chop) using the linear mixed model to determine the mean change in the variables (Visual acuity, loss of corneal endothelial cells and Central corneal thickness) between baseline and four weeks. Test results will be given to participants taking into consideration the primary variable change from baseline to the timeframe evaluated throughout the trial (post op day 1 and after the end of 4 weeks after completion of intervention). While fixed effects will be examined by taking the treatment group and number of visits into account, random effects will be generalized for study subjects. From the Baseline till the last visit at 4 weeks, the effect size over the mean change difference on the primary variable will be assessed, and the associated 95 percent Confidence Interval will be given.