CAPSULaser – a new modality in the portfolio of cataract surgeons

Abstract

To assess the efficiency and safety of capsulorhexis with CAPSULaser in comparison with standard capsulorhexis performed manually by emerging and established surgeons. Specialized Eye Hospital–Varna Bulgaria. Prospective, randomized, non-masked study. Patients were randomized to the M group (manual CCC), L group (laser CCC), and 2 surgeons. The manual CCC was targeted at 5.5 mm. The laser CCC was sized at 5.3 mm and measured with the same caliper device during photomicroscopy. The inclusion criteria were otherwise healthy eyes with cortical, nuclear, or subcapsular cataracts of any maturity with a biomicroscopically deep anterior chamber and preoperative pupil wider than 6.5 mm. The surgical time was measured for the entire procedure and only for capsulotomy. Sixty eyes of 60 patients, aged 65.8 ± 11 years, were prospectively recruited. Two surgeons (one with 3 years and one with 30 years of experience) performed the same types and number of procedures. The experienced surgeon was 2 times faster when performing manual capsulorhexis, but the time for CAPSULaser was almost the same. The size of the “laser” CCC was planned to be 5.3 and ended up with a minimum of 5.4 in 4 weeks; however, no lens prolapse from the CCC was observed. Utilization of the CAPSULaser in cataract surgery is easy and achievable for surgeons at any stage of their careers and provides controlled, well-centered capsulorhexis with no more adverse events than conventional surgery. The limitations are the requirement for a minimal pupil size of 6 mm, a deep anterior chamber, and a transparent cornea.

1. Introduction

Currently, continuous curvilinear capsulorhexis (CCC) is the gold standard for capsular opening and a key step in phacoemulsification. The first paper on the advantages of this concept was published in 1990 by Gimbel and Neuhann, although there is empirical proof that Calvin Fercho was practicing these techniques 10 years earlier.^[1] Since then, much work has been done to achieve better precision in the size, centration, and predictability of CCC. The introduction of capsular staining at the end of the last century was a significant step toward providing better visualization and handling.^[2] Further research and development resulted in the introduction of external and internal markers such as projection overlays (Verion; Alcon, USA), Callisto (Zeiss, Germany) or “Tassignon ring,” and various different dedicated devices most popular of which are the femtosecond laser and precision pulse capsulotomy (Zepto).^[3] Main advantages of these innovations are CCC precise sizing and centration, stronger capsular rim, minimal trauma, and modifiable training curve, all of which vary for each device. The disadvantages are specific, but price and/or multiple more invasive steps are probably the universal cones highlighted in the literature.^[4–6] Furthermore, CCC is easy in standard straightforward cases, but in small pupils, shallow anterior chambers, unstable crystalline lenses, and combined procedures, performing capsulorhexis might be a real challenge with consequences compromising the steps to follow.

To address the aforementioned obstacles and provide a noninvasive, uniform, and well-centered capsulorhexis, a new method named CAPSULaser was developed.^[3] We report our first 60 cases performed with this new device to assess efficiency (uniformity in size, centration, and surgical time), safety (complications and additional steps required), and compare them with standard capsulorhexis performed manually by the same surgeons. We concentrated on comparing established and newly trained eye surgeons, because this step is usually the most challenging for many trainees, and a small mistake in it might be associated with many more surgical complications.

2. Methods

2.1. Subjects and selection criteria

Sixty eyes of 60 patients (28 male and 32 female), aged 65.8 ± 11 years, were prospectively recruited in the clinic. The study was approved by the local ethics committee (ref 907:20.08.22) and all subjects provided informed consent. The inclusion criteria were otherwise healthy eyes with cortical, nuclear, or subcapsular cataracts of any maturity with a biomicroscopically deep anterior chamber and preoperative pupil wider than 6.5 mm. All patients were willing to accept a new step, monitor their routine operation, and demonstrate good self-control and the ability to stay steady. Patients with diabetes and other endocrine and renal diseases were also excluded, as were patients taking multiple (more than 3) systemic medications. Preoperatively, patients were dilated with tropicamide (1%) and cyclopentolate (1%), but not with neosinefrine (10%). Preoperative evaluation included visual acuity testing with a LogMar visual acuity chart, IOP (Corvis^® ST; Oculus Inc.), biomicroscopy (ZEISS SL 220 and ZEISS SL Imaging Module), specular microscopy (2000P Topcon specular microscope), and posterior segment OCT (Cirus 6000, Zeiss). Postoperative evaluation included visual acuity testing with the LogMAR visual acuity chart (1 and 4 weeks after surgery), IOP (1 and 4 weeks after surgery), biomicroscopy (1 and 4 weeks after surgery), specular microscopy (4 weeks after surgery), and posterior segment OCT only in cases with decreased vision. Surgical time was measured for the entire procedure (from cleaning of the field to the postsurgical bandage) and only for capsulotomy (from the main incision to hydrodissection). Patients were randomized to 2 surgeons and 2 groups: the M group (manual CCC) and the L group (laser CCC). The manual CCC was targeted at 5.5 mm. The laser CCC was sized at 5.3 mm and measured with the same caliper device during photobiomicroscopy at 4 weeks.

2.2. CAPSULaser

CAPSULaser (EXCEL-LENS, Inc., Livermore, CA) is a class 4 solid-state laser with a wavelength of 590 ± 3 nm and 100% continuous wave. The device is easily attached to the surgical microscope and has a separate pedal manipulation. The laser had to run a standardized procedure before the surgical day. Each procedure was endorsed by using a software key. The size of the CCC can be set from 4.0 to 5.5 mm in diameter in 0.1 increments. The mechanism of action involves selective absorption of the stain with the trypan blue anterior capsule.

2.3. Surgery

The 2 surgeons performed the same type and number of procedures, one with 30 and one with 3 years of surgical experience (300 + cataract procedures), and assigned the cases randomly. After peribulbar anesthesia, the patient was positioned on the surgical table and the eye was draped. The main incision was made.

For the M group the capsule was stained with CapsulBlue ® (EXCEL-LENS, Inc.). After 60 seconds, the dye was meticulously washed out with balanced salt solution (BSS®; ALCON, Fort Worth, TX), and the anterior chamber was filled with cohesive visco-substance (DisCoVIsc®; ALCON). Utilizing Utrata forceps, a manual capsulorhexis aimed to be 5.5 mm in diameter was performed under the Callisto eye (Zeiss Inc) guidance. The central stab was followed by a flap at the 3 o’clock position and moved clockwise until complete CCC was achieved.

In the L group, the ocular surface was covered with methylcellulose, and the anterior chamber was filled with Capsulblue® (EXCEL-LENS, Inc.) under air. The cannula was directed towards the capsule at the 6 o’clock position to provide uniform, more intensive staining. After 60 seconds, the dye was meticulously washed out with a balanced salt solution (BSS®; ALCON), and the anterior chamber was filled with cohesive visco-substance (DisCoVIsc®; ALCON). Following the prior calibration and verification procedure, the Laser device (CAPSULaser®) was advanced to the surgical field. The beam was focused according to the manufacturer’s recommendations. Centration was performed based on the marks formed during capsular staining. The size and concentration of the capsulohexis were verified, and the laser was fired with an intended diameter of 5.2 (Fig. 1). The round capsular segment was extracted using Utrata forceps, and the operation was continued in a standard manner.

Figure 1.

The most important steps of capsulotomy performed with CAPSUlaser: techniques for staining with Capsulblue® (EXCEL-LENS, Inc., Livermore, CA) (A), wash out and filling of the anterior chamber with viscoelastic(B), performing the laser for less than a second, assisting eye stabilization (C), removal of the intact capsular segment with Utrata forceps (D).

The efficiency and safety was evaluated on the basis of the following criteria:

Primary efficiency parameters were the size and absence of defects of the capsulorhexis margin at the end of the surgery and the surgical time from the first incision to hydrodissection. Secondary parameters included intraocular lens in-the-bag centration and absence of imperfections at the edge of the capsulorhexis 4 weeks after the surgery.

The primary safety parameters were endothelial cell count, IOP, 360-degree continuous curvature, and centration of the capsulorhexis, and secondary parameters were based on descriptive events such as laser damage of the corneal epithelium, stromal marks, and/or iris damage.

As the methodology was new for both surgeons, they were allowed to make specific procedure-related comments at the end of the 15-th laser-assisted surgery.

3. Results

Sixty eyes from 60 patients were surgically treated. They were randomly assigned to Surgeon 1 (groups 1 M and 1 L) and Surgeon 2 (groups 2 M and 2 L) Demographic and preoperative parameters are presented in the Table 1. Total surgical time and the time dedicated to performing capsulotomy by the 2 methods are shown in Table 2.

Table 1.

Demographic parameters of the study subjects. Group 1 was operated by an established surgeon (30 + years of surgical experience). Group 2 was operated by a young experienced surgeon (300 + cataract cases). The sub-groups M and L were randomized to manual (M)l and laser(L) (Capsullarer) capsulorhexis respectively.

Parameter	Group 1M N = 15 eyes	Group 1L N = 15 eyes	Group 2M N = 15 eyes	Group 2L N = 15 eyes	Total N = 60
Age	63.7 ± 9	65.8 ± 12	68.9 ± 11	65.8 ± 12	66.3 ± 11
Gender	M = 7, F = 8	M = 6, F = 9	M = 7, F = 8	M = 7, F = 8	M = 27, F = 33
Mean visual acuity (LogMar)	0.84	0.76	0.75	0.76	0.8
IOP (Goldmann tonometer)	13.4 ± 4	13.3 ± 4	14 ± 2	13.6 ± 2	13.6 ± 3
Range of IOL power	13-28 D	14-29 D	12-28 D	16-27 D	12-29 D
Preoperative endothelial cell count	1829 ± 292	1838 ± 278	1849 ± 307	1802 ± 282	1826 ± 287
Type of cataract (C-cortical, N Nuclear, S sub-capsular. T-total)	C = 7, N = 4, S = 0, T = 4	C = 9, N = 2, S = 2, T = 2	C = 9, N = 3, S = 2, T = 1	C = 9, N = 2, S = 2, T = 2	C = 34, N = 11, S = 6, T = 9

Table 2.

Total surgical time and the time dedicated to capsulotomy, and specific pre- and postoperative outcome parameters in 1 and 4 weeks. Group 1 was operated by an established surgeon (30+ years of surgical experience). Group 2 was operated by a young experienced surgeon (300+ cataract cases).

Parameter	Group 1M N = 15 eyes	Group 1L N = 15 eyes	Group 2M N = 15 eyes	Group 2L N = 15 eyes	Groups M N = 30 eyes	Groups L N = 30 eyes	Statistical difference M versus L, P value
Total surgical time (min)	12 ± 2.2	13 ± 1.9	15 ± 1.7	17 ± 1.5	13.5 ± 2	15 ± 1.7	.0006
Procedure dedicated time	0.6 ± 0.15	2.99 ± 0.25	1.3 ± 0.13	3.26 ± 0.15	0.95 ± 1.4	3.13 ± 2	.0001
Mean visual acuity (1 wk) (LogMar)	0.21	0.21	0.16	0.17	0.19	0.19	.1
IOP (Goldmann tonometer) 1 wk	14.4 ± 3	15.3 ± 4	13.9 ± 2	13.2 ± 2	14.2 ± 2.5	14.3 ± 3	.08
IOP (Goldmann tonometer) 1 wk	12.4 ± 3	12.3 ± 4	13 ± 2	12.6 ± 2	12.7 ± 2.5	12.5 ± 3	.09
Mean visual acuity (4 wk) (LogMar)	0.03	0.05	0.04	0.03	0.04	0.04	.2
Postoperative endothelial cell count (4 wk)	1734 ± 290	1716 ± 295	1601 ± 247	1683 ± 297	1667 ± 269	1692 ± 296	.2
Size of the capsulorhexis (4 wk)	5.3 ± 1.2	5.5 ± 0.8	5.4 ± 1.6	5.5 ± 0.6	5.4 ± 1.4	5.5 ± 0.7	.02

The size of the capsulorhexis was determined by the 2 surgeons manually and with the assistance of CAPSUlaser, as shown in Figure 2. Decentered capsulorhexis was observed in 1 patient from group 1 L and 2 patients from group 2 M. In all 3 cases, the decentration was within 1.5 mm. In both L groups, there was a case with incomplete capsulorhexis with 1 to 2 clock hours bridge, which was easily completed without prolongation of the procedure. In only one case (group 2 L), decentration and incomplete capsulorhexis resulted in 1 mm lens decentration and BSCVA 0.8 at 4 weeks, which was the worst of the entire group (2 L). Three cases, including the last one, had a BSCVA of 0.8, and underwent OCT within 4 weeks. No macular edema was observed in these cases. Corneal marks were observed in 3 patients (2 from group 2 L) and disappeared completely within 1 week. One patient with a corneal mark (group 1 L) experienced mild discomfort for 1 week. Two patients from group 2 M had an oval-shaped capsulorhexis. One patient in group 1M had a capsular snap during phacoemulsification.

Figure 2.

The size of the capsulorhexis was performed with CAPSULaser by surgeon 1 (red) and 2 (blue), and manually in lighter green by surgeon 1 and darker green by surgeon 2 respectively. Note the big standard deviation for the manual capsulorhexis performed by the younger surgeon.

The size of the CCC was planned to be 5.3 mm and ended with a minimum of 5.4 mm in 4 weeks; however, no lens prolapse from the CCC was observed in any of the included eyes.

Comments of surgeon 1: The device changes the feeling for manual microscope adjustment and significantly slows the capsulorhexis step; however, it provides uniform CCC without pressure on the capsule and zonules and is ideal for hypermature, eventually subluxated, and complicated cataracts, as well as for cases with high demand for precision.

Comments of surgeon 2: The device decreases the free space between the patient and the microscope and slows the capsulorhexis step, but is a very useful device for uniform capsulorhexis with robust edges.

4. Discussion

The demand for precision in cataract surgery is increasing, and is mainly addressed by femtosecond laser cataract surgery (FLACS). Together with the expenses of the equipment and each procedure, this methodology requires additional skills and staff. In an elegant experimental study on cadaver eyes, Daya et al demonstrated the inferiority of the strength of femtosecond CCC in comparison to manual and thermal laser performed with CAPSUlaser.^[7,8] Furthermore, Sharma et al demonstrated a significantly higher risk of capsular tear in 1626 cases randomized to manual and femtosecond surgery.^[4] In addition to providing robust and uniform capsulorhexis, CAPSULaser is also a much simpler, dedicated device, which would work in the hands of any trained surgeon, regardless of their experience, at a lower expense (investment and procedure cost). As a new method, efficiency and safety are the 2 main pillars for establishing the methodology. In our small pilot study, we did not experience any serious safety issues during the learning curve of established and less experienced surgeons. The senior surgeon also had a slight but statistically significant increase in the surgical time. This procedure was even more time-consuming for younger surgeons. However, the time required for FLACS is even longer.^[7] FLACS surgery also requires a separate laser platform and special docking device, which makes it more complicated for busy small-to medium-sized practice. CAPSUlaser is easy to attach to the operating microscope, and although our surgeons mentioned that it slightly decreases the surgical space and changes the free movement of the microscope arm, it does not complicate the surgical theater and affects the workflow of the surgeon and one technician, not the other staff.

This new methodology has some specifics. The most complicated step during the procedure is staining, which can be up to 10% of the entire procedure and definitely more than 50% of the capsulorhexis step. However, this time-consuming step is crucial for the quality of laser capuslorhexis. This step is also important for preventing complications because staining of adjacent structures may lead to transient damage of the epithelium or stroma. Although staining was performed according to the protocol in our group, we had 3 cases of tissue injuries, all of which resolved without additional treatment. This may be attributed to the learning curve of the surgeons.

In our pilot study, we evaluated 2 surgeons. The younger patients were slightly slower; however, the speed of the surgery was not a criterion for quality. Another interesting fact is the standard deviation when performing manual capsulorhexis, which was significantly wider for the less experienced surgeon. This is probably one of the most significant advantages of the capsulolaser, which provides repeatability and uniformity regardless of experience, and therefore, less human dependence. In a way, this is a gateway to automatic steps with the aforementioned lower expenses and set up complexities.

When the endothelial dynamics are considered, the technique is not really comparable with FLACS because of the other steps involving femtosecond applications, nor with Zepto, as the entire device is positioned in the anterior chamber.^[7] Looking into these outcome parameters, the procedure is comparable (or superior, neither inferior) to the standard capsulorhexis. However, our surgeons were well-trained. In more diverse cohorts of less experienced surgeons, capsulorhexis performed manually might cause more endothelial damage. The similar are the results regarding IOP, which was without peeks in the laser groups, probably because the technique is “no touch.”

The postoperative results at 4 weeks demonstrated excellent outcomes in both groups; however, the centration of the IOL’s after laser capsulorhexis was appreciated better by the assessors. This study did not include toric, extended depth of focus, or multifocal lenses. In the case of premium lens implantation, the results might be different, as already demonstrated for more-controlled femto-assisted capsulorhexis.^[7,9]

Finally, the senior surgeon pointed out that CAPSULaser CCC would be beneficial in subluxed, hypermature, and other complex cases. In fact, the team already has excellent experience with some casuistic surgical situations where the speed and minimal mechanical effect on the lens have the advantage of performing CCC, implanting intracapsular ring, successful surgery with excellent IOL centration, and no complications. Further studies and observations would help to implement this technique in conventional and special cataract surgery procedures and evaluate the long-term results.

Utilization of the CAPSULaser in cataract surgery is easy and achievable for surgeons at any stage of their career. It has a learning curve and increases the surgical time of the capsulorhexis step because of the prolonged staining time (60 s). However, it provides a controlled, well-centered capsulorhexis with no more adverse events than conventional surgery. Therefore. It is a safe technique that can be implemented in everyday practice, especially when precise, fast, and minimally traumatic capsulorhexis is required. The limitations are the requirement for a minimal pupil size of 6 mm, deep anterior chamber, and transparent cornea, which may not allow the application of this methodology in all complicated cases.

Acknowledgments

We acknowledge the contribution of David Mordaunt for statistical advice and proofreading.

Author contributions

Conceptualization: Christina N. Grupcheva.

Data curation: Christina N. Grupcheva, Dimitar I. Grupchev.

Formal analysis: Christina N. Grupcheva, Dimitar I. Grupchev.

Investigation: Christina N. Grupcheva.

Methodology: Christina N. Grupcheva, Dimitar I. Grupchev.

Project administration: Christina N. Grupcheva.

Software: Christina N. Grupcheva, Dimitar I. Grupchev.

Supervision: Christina N. Grupcheva.

Validation: Christina N. Grupcheva, Dimitar I. Grupchev.

Visualization: Christina N. Grupcheva.

Writing – original draft: Christina N. Grupcheva, Dimitar I. Grupchev.

Writing – review & editing: Christina N. Grupcheva, Dimitar I. Grupchev.