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Dr. Gopal Damani, Dr. Swyambhu Prosad Ghosh, Dr. (Mrs.) KELKAR JAI ADITYA, Dr. AKSHAY KOTHARI

Continuous curvilinear capsulorhexis (CCC) is of utmost importance while performing phacoemulsification and it significantly determines the overall success of cataract surgery.[1] Thus, the need to have a perfectly sized and circular rhexis cannot be overemphasized. It offers various advantages like optimal intraocular lens (IOLs) centration, and reduced chances of posterior capsular opacification.[2‑4] Manual capsulorhexis is currently the most commonly employed capsulorhexis technique. But it has a substantial learning curve and may not be consistently accurate in size and shape especially in inexperienced hands. All the more, the advent of premium IOLs like multifocal and toric IOLs has necessitated a perfect capsulorhexis.[5‑7]

The risk of capsulorhexis runoff and capsular tags with capsulotomy techniques, endanger the effective placement of these IOLs and further outcome of phacoemulsification surgery. In order to overcome these problems, new technologies like femtosecond and precision pulse capsulotomy (PPC) have been introduced, but they too come with their own set of challenges. Femtosecond laser assisted capsulotomy is precise in terms of the shape and size of the capsulotomy but involves high cost, and increased operative time.[8‑11] In 2017, Mynosys Cellular Devices Inc. (Fremont, CA, USA) developed a PPC, under the trade name “Zepto,” a new capsulotomy technology that works on the principle of converting very fast electrical pulses into mechanical energy in millisecond timeframe.[1] In this article, we have compared the three different types of capsulorhexis techniques in our setting.

Methods

This was a rerospecie case study of patients who underwent phacoemulsification with IOL implantation using PPC technique at a tertiary eye care center. We adhered to all tenets of declaration of Helsinki. Institutional Ethics Committee approval was obtained for this study. Informed written consent was taken from all patients preoperatively. Exclusion criteria for our study included patients with pre-existing ocular pathologies like retinal conditions or glaucoma, subluxated or traumatic cataract, complicated/uveitic cataract, zonulopathies, and patients who did not follow up. All surgeries were performed by two experienced surgeons. Cataract grading was done on slit lamp examination preoperatively.

All aseptic precautions were observed and all surgeries were performed under topical anaesthesia. Two paracentesis ports were created using a 15 degree lance tip at 3 and 9 o’clock positions. A 2.8 mm clear corneal incision was made superiorly with a disposable keratome in all cases. Trypan blue was used for clear visualization of the anteriorcapsule in all mature cataract cases and cases with poorly dilating pupil.

Either of the three capsulorehxis techniques was applied to create an opening into the anterior capsule. In ManualContinuous curvilinear capsulorhexis the anterior chamber was filled with Ocular viscosurgical device (OVD) and the capsulorhexis is performed using a bent 26G cystitome needle or forceps.

For the FemtoSecond Laser Capsulotomy,  seyewasdockedtothesystemusing a suction device coupled to the laser. After the anterior  sed,anddisplayedwith the integrated OCT, the surgeon selected the treatment patterns and, if necessary, adjusted the laser parameters based on the anatomy and orientation of the eye. After that, a capsulotomy was performed. Stablepositioningduringlasertreatmentwasachievedby the LiquidOptics patient interface (OptiMedica Corp.), consisting of a suction ring and liquid immersion lens.

This approachenablesdockingtooccurwithonlyasmallriseinthe intraocular pressure (15 mm Hg), avoiding patient discomfort or amaurosis. In addition, the cornea does not fold because no hard lens surface contacts the patient’s cornea directly.Avoidingcornealfoldsisveryimportantforprecise cutting as folds distort the beam.  systemiscoupledtotheeyethroughdocking, a long-range spectral-domain OCT imaging system isused to obtain a 3-D map of the patient’s anterior segment and both surfaces of the lens, and the near-infrared video provides a live image of the eye.

Image processing software automatically identifies anterior and posterior corneal surfaces, iris, and anterior and posterior lens surfaces and overlays the prospective capsulotomy and lens fragmentation patterns on the OCT data on a graphic user interface for the surgeon’s review. The overlaidnear-infraredvideoenablesthesurgeontoverifylateral position of thelaser patternsandcontrol everyaspect of the laser capsulotomypatternisaposterior to anterior spiral, starting in the anterior lens tissue and terminating inthe lower endof theanterior chamber toensure intersection of the incision with the anterior lens capsule in between.

The Precision Pulsed Capsulotomy device is primed using balanced salt solution and then the slider was extended forward onto the handpiece by the surgeon, thus elongating the PPC tip. The tip was then introduced through the main incision into the anterior chamber filled with OVD, after stabilizing the eye with corneal forceps if required. Once the tip was in the anterior chamber, the push rod was retracted completely and the device re‑expanded to its inherent circular shape. The PPC tip was then centered over the desired capsulotomy site and controlled suction was applied via the console system. Eventually, a waveform was created that formed the capsulotomy opening. Suction was released and tip was gently removed from the anterior chamber.

After completing the capsulotomy, the free floating anterior capsule was removed and then both the capsule and capsulotomy edge were inspected for any residual tag or tear. Also the size and shape of the capsulotomy edge were observed. Direct chop phacoemulsification was performed using the Stellaris System (Bausch and Lomb). After performing bimanual irrigation and aspiration, single piece aspheric hydrophobic acrylic IOL (AcrySof IQ, Alcon Labs, Fort Worth, TX, USA) implantation was done in all patients.

Patients were followed up at day 1, 2nd week, 3rd, and 6th months. Best‑corrected visual acuity (BCVA),capsulotomy edge, posterior capsular opacification, anterior capsular opacification/contraction, IOL stability, and centration were evaluated at 3rd and 6th months.

RESULTS

This study included patients who underwent Phacoemulscification with posterior chamber intraocular lens implantation being divided into 3 groups according to method of capsulotomy performed- Manual CCC, FSLC, and PPC with each group having 123 eyes, similar grade of cataract and demographic characteristics.The mean age was 49.5 (±7.77) years with a range of 30–81 years. The cataract grade was nuclear sclerosis (NS) I in 31 eyes, NS II in 55 eyes, NS III in 11eyes, NS IV in 12 eyes, and mature cataract in 14 eyes in each group. Postoperatively BCVA improved to 6/9 or better in all patients. The mean preoperative IOP was 15.21 ± 2.85 mm Hg and mean postoperative IOP was 15.65 ± 2.65 mm Hg. At 6 months, one case developed anterior capsular opacification at the capsulotomy edge and none of the eyes had any visually significant posterior capsular opacification or capsular contraction. All cases had well‑centred IOL with stable fixation.

Complications faced in Manual CCC

One patient had a rhexsis run-off, but was managed with careful phaco to get desirable outcome. Shape of the rehxis was slightly irregular in 86 eyes but it did not compromise on the visual outcome nor the anterior or posterior capsular opacification. The mean size of capsulorehxis was 5 mm.

Complications faced in FemtoSecond Laser Capsulotomy

We faced no complications in FSLC and could achieve perfect circular capsulotomy in all cases. The mean size of capsulorehxis was 5.25 mm.

Complications faced in Precision Pulsed Capsulotomy

One hundred seventeen eyes had complete round circular capsulotomy edge without any intraoperative complications. In one case, sub-incisional iris was inadvertently caught in the suction cup that was released and then the tip was re‑introduced resulting in a circular capsulotomy ultimately. In five cases the capsulotomy edge was noted to have extended to the periphery sub-incisionally. In one case of mature cataract, a small capsular tag was noted inferiorly and sudden extension of capsulorhexisoccurred from the capsular tag after removal of irrigation and aspiration cannula. We encountered probe malfunction in six cases. In these cases, while extending the push rod, it penetrated through the silicon cup thus making it non-functional. Thus, a new handpiece was used to complete the capsulotomy. The rest of the surgery was uneventful.

There was no difficulty observed in hydro dissection, nucleus rotation or cortical clean up, and in none of the patients posterior capsular tear or vitreous loss was encountered. The comparison data of the three techniques of capsulorhexis are presented in Table 1.

Parameters Manual (n=123) Femto (n=123) Zepto (n=123)  

P‑values (intergroup)

 
        Manual vs Femto Manual vs Zepto Femto vs Zepto
Mean age (years) 56.1 56.3 55.9 0.999NS 0.999NS 0.999NS
Sex
Male 86 (70.0) 83 (67.5) 82 (66.7) 0.999NS 0.999NS 0.999NS
Female 37 (30.0) 40 (32.5) 41 (33.3)
Rhexis runoff 1 (1.6) 0 6 (4.9) 0.999NS 0.165NS 0.039*
Mean size (mm) 5.00 5.25 5.20 0.999NS 0.999NS 0.999NS
Shape        
Irregular 86 (70.0) — 6 (4.9) 0.001*** 0.001*** 0.087NS
Circular 37 (30.0) 123 (100.0) 117 (95.1)

Table: Values on sex, rhexis runoff, shape, and centration are n (% of eyes) and the P value by Chi-square test. P values for mean age and mean size are by ANOVA. Bonferroni’s correction is used for multiple group comparisons for both Chi-Square and ANOVA comparisons. P value < 0.05 is considered to be statistically significant

The distribution of mean age and sex did not differ significantly across the three study groups (P value> 0.05 for all). The distribution of shape differed significantly in manual and Zepto groups (P value < 0.001). It did not differ significantly between femtosecond and Zepto groups (P value > 0.05). The incidence of rhexis runoff was higher in Zepto than manual group but it was not statistically significant. Whereas, it was significantly higher in Zepto compared to femtosecond (P value < 0.05). The distribution of mean size did not differ significantly across the three study groups (P value > 0.05 for all).

DISCUSSION

It was Howard Gimbel and Thomas Neuhann, who pioneered the manual capsulorhexis technique that revolutionized the phacoemulsification surgery.[12] Traditionally, surgeons have been successfully performing the manual CCC with needle or forceps but it does have a learning curve. Automated CCC can be performed using the femtosecond laser;[8,9,13,14] however it is expensive, and is difficult to perform in cases with mature cataracts, small pupils, and corneal opacities. Another laser‑assisted system “CAPSULaser” has been introduced recently.[15] It is a microscope mounted, noncontact, continuousmode laser system that produces a stronger capsulorhexis with better elasticity.[15] However, it is not yet commercially available.

In the quest of achieving a perfectly sized and circular rhexis, Mynosys developed PPC under the trade name Zepto in 2017. A disposable handpiece is provided along with a console that regulates the vacuum during the procedure. The tip consists of a circular nitinol ring element for a 5.2 mm diameter capsulotomy and is covered by a silicone suction cup that ensures favorable apposition of the ring to the anterior capsular surface. The nitinol alloy has good memory, which ensures adequate deformation of the tip whereas maneuvering through the main incision port. A series of brief fast electrical micropulses create optimum heat to vaporize the water molecules trapped between the anterior capsule and the nitinol ring.

The phase transition happens so rapidly that a simultaneous circular anterior capsulotomy is created.[16]PPC technique is also an attempt to overcome the pitfalls of performing manual CCC. PPC may be advantageous in challenging case scenarios like mature cataracts, intumescent cataracts, coexisting significant pterygium, and poorly dilating pupils but care must be exercised as the technique is not free of complications. Studies conducted in live rabbits and human cadaver eyes reported that PPC is safe, effective, and produces a stronger capsulotomy edge compared to manual and FLSC technique with no difference in postoperative corneal edema, endothelial cell loss, inflammation, and capsular opacification.[17,18]

The placement of the IOL was stable and well centered in all cases. However, we wish to emphasize the fact that the centration of the ring over the anterior capsule is with relation to the iris rim and also surgeon dependant or manual leading to a few off‑centered capsulotomies. But these off‑centrations were not significant in relation to IOL centration and stability. To overcome this difficulty, Waltz et al. have recommended placement of the center of the PPC device on the appropriate Purkinje image allowing centration of a PPC capsulotomy on the patient’s visual axis.[16]

In cases with small pupils, the use of the PPC device is safe because the silicone material forming the suction cup is soft and insulates against heat as shown in a previous study, which reported only a slight temperature change (1 to 2 degrees) immediately adjacent to the suction cup during capsulotomy.[16] At 6 months, we did not encounter any IOL instability, capsular contraction, and PCO that is similar to earlier reports.[17] Although, in one case we observed anterior capsular opacification at the capsulotomy edge at 6 months follow‑up. A study was carried out in human cadaver eyes that tested and compared the tear strength of manual, femtosecond, and presicion pulse capsulotomy.[18] It showed that the strength of the capsulotomy edge was greater in PPC as compared to other two techniques.

In our study, we encountered maximum rhexis runoffs in PPC group (4.9%) followed by manual (1.6%) followed by femtosecond (0%) group. The difference between PPC and femtosecond group was statistically significant (P = 0.039). As far as rhexis runoff is concerned, we believe that manual capsulotomy once mastered can give results better than PPC and similar to femtosecond laser assisted capsulotomy. Thus, manual capsulorhexis can still be considered the technique of choice especially where affordability is an issue.

Conclusion

PPC is a useful device for achieving a perfectly round capsulorrhexis. However, the technique has a learning curve and subincisional area can have skip areas leading to torn capsulorhexis. Chances of capsular tag and its extension should also be kept in mind. Special care should be taken in the initial cases and while operating on eyes with poorly dilating pupil, and mature cataract and cataracts with shallow anterior chamber. Future larger clinical studies comparing the manual versus automated capsulotomy techniques in human eyes would help us better understand the long‑term safety and efficacy of all these procedures.

Financial support and sponsorship Nil.

Conflicts of interest There are no conflicts of interest.

 References

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  11. Reddy KP, Kandulla J, Auffarth GU. Effectiveness and safety of femtosecond laser–assisted lens fragmentation and anterior capsulotomy versus the manual technique in cataract surgery. J Cataract Refractive Surg 2013;39:1297‑306.
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