Devices adapted to C-MICS phaco

By Franck Fajnkuchen, MD

Editor’s Note: Since the introduction of microincision cataract surgery (MICS), it has been known that the reduction in incision size may complicate capsulorhexis management. Particularly, for incisions below 2 mm, the handling of capsulorhexis forceps can be made more difficult. Therefore, in recent times, forceps dedicated to coaxial MICS (C-MICS) incision have been developed. In this article from Ophthalmology Times Europe, Franck Fajnkuchen, MD, discusses the results of a recent comparative study examining the relevancy of using devices dedicated to standardizing capsulorhexis creation during a 1.8 mm C-MICS phacoemulsification procedure.

Since the introduction of MICS, we know that the reduction of the incision size may complicate capsulorhexis management, particularly regarding the capsulorhexis step. Indeed, below 2 mm, a narrow incision tends to make the handling of the capsulorhexis forceps more difficult and may compromise the realization of an optimal capsulorhexis.

In the past few months, forceps dedicated to C-MICS incision have been developed. In a previous study, we have shown a high level of efficiency and safety, and no major difficulties, using this kind of device. However, we did not evaluate then the capsulorhexis quality created with these forceps.¹

To improve the quality of this step, we decided to evaluate the relevancy of using devices dedicated to standardizing capsulorhexis creation during a 1.8 C-MICS phacoemulsification procedure; and to assess the impact of these instruments on the size, shape and centration of the capsulorhexis.²

Patients and method

We performed a propspective study including 36 consecutive cases of capsulorhexis performed by 2 residents using 1.8 mm C-MICS phacoemulsification. The population was randomly distributed into 3 groups and the capsulorhexis was done using three different devices (Figures 1 to 3):

• A single-use capsulorhexis forceps (SUE06, Bausch + Lomb), Group 1.

• A single-use forceps with measuring marks at 5.5 and 6 mm (SUE07, Bausch + Lomb), Group 2.

• A 6-mm diameter corneal marker used to draw a guide on the cornea before performing the rhexis with a standard single-use forceps (E9036 + SUE06, Bausch + Lomb), Group 3.

The above forceps were specifically designed for MICS surgery.

The following parameters have been analyzed: diameter, centration, and regularity of the caspulorhexis, and duration of the rhexis procedure, as well as intraoperative complications (capsular tear, posterior capsule rupture). The subjective degree of difficulty in creating an optimal capsulorhexis was also evaluated using a questionnaire.

Results

The first objective of this study was to assess if the capsulorhexis diameter was close to 5.5 mm, and to estimate if this diameter had good reproducibility (estimated from the standard deviation).

There was no difference in the mean capsulorhexis diameter between group 1 and group 2. In both groups, mean vertical and horizontal diameter were not so far from the 5.5 mm ideal rhexis diameter (Table 1). However, the reproducibility of the capsulotomy size was better in group 2 (forceps with measuring marks) than in group 1 (standard forceps), as we observed based on the standard deviation.

Indeed, in group 1 (forceps without measuring marks) the standard deviation concerning the horizontal diameter was 0.66 mm versus 0.27 mm in group 2 (forceps with measuring marks). The vertical diameter standard deviation was 0.59 mm in group 1 versus 0.23 mm in group 2. In group 3,the capsulotomy reproducibility was good, but the capsulorhexis diameter was smaller than in the other two groups, below 5 mm: the mean capsulorhexis horizontal diameter is 4.93 mm and the mean vertical capsulorhexis diameter is 4.74 mm.

For all groups, we observed that the horizontal diameter was larger than the vertical diameter (Figure 4). This was due to a restricted range motion of the forceps close to the incision, which subsequently reduces the vertical diameter.

We have also evaluated the rate of occurrence of small or large caspulorhexis. Small capsulorhexis (with one diameter below 5 mm) were frequent in group 1 (33%) and group 3 (58%), and were uncommon in the second group with a rate of 8.5%. Large capsulotomies were infrequent in all groups with C-MICS technique.

We have evaluated the capsulorhexis regularity by measuring the difference between the vertical and horizontal diameter. The rhexis has been rated as irregular (with a difference between the vertical and the horizontal diameter more the 0.5 mm) in no case in group 2 (forceps with measuring marks) and in two cases in each of the two other groups.

Concerning capsulotomy centration, with an overlap of the rhexis on the IOL throughout 360°, it was only achieved in 58% of cases in groups 1 and 2, and in all cases in group 3 (corneal marker and standard single use forceps), but in this last group, this objective was achieved at the cost of smaller capsulorhexes.

There was no significant difference in capsulorhexis duration found between the different groups (Table 2).

The capsulorhexis forceps with marks was judged very easy to use in most of the cases, the learning curve being limited to one procedure. Conversely, the residents judged the corneal marker uncomfortable to use in half of the cases. No complications occurred in the three groups.

Discussion

It is mandatory to create an optimal capsulorhexis: to reduce the incidence of

posterior capsule opacification and to ensure refractive stability. Adequate size, circularity and good centration are required to create a high quality capsulotomy. Creating a good quality continuous curvilinear capsulorhexis (CCC) can be difficult, especially for trainee surgeons. Moreover, creating a capsulorhexis through a small incision (<2 mm) may enhance the difficulty of this stage. Previous methods have been used to standardize the CCC: ring shaped caliper,³ corneal marker,⁴ cross‑action capsulorhexis forceps with marks on the tip.⁵

In the present study, we have compared different devices adapted to C-MICS phacoemulsification and we have shown that methods dedicated to standardize the capsulotomy allowed a better reproducibility compared to the free-hand method. The capsulotomies created with the single-use forceps with marks show a good size (close to the ideal 5.5 mm), a good reproducibility, with a very short learning curve. A good centration was sometimes difficult to achieve. Corneal marker assisted capsulotomies were often too small.

In conclusion, the capsulotomies created with single‑use forceps with marks, and dedicated to C-MICS, were more precise in terms of size and shape compared to the other methods. The single‑use capsulorhexis forceps with markings have allowed us to create a higher‑quality capsulorhexis.

References

1. Fajnkuchen F et al., CMICS 1.8 mm: Capsulorhexis Learning Curve of Resident Surgeons, ASCRS, San Diego, CA, March 2011.

2. Fajnkuchen F et al., 1.8 mm CMICS and Devices Dedicated to Realization of Optimal Capsulorhexis, Poster presented at the ESCRS Congress, Milan, Italy, September 2012.

3. Tassignon MJ, Rozema J, Gobin L. A ring-shaped caliper for better anterior capsulorrhexis sizing and centration. J Cataract Refract Surg. 2006;32:1253-1255.

4. Wallace RB. Capsulotomy diameter mark. J Cataract Refract Surg. 2003;29:1866-1868.

5. G. Ratnaran et al., J. Cataract Refract. Surg. 2011;37:1559–1560.

Franck Fajnkuchen, MD, is hospital practitioner at Hôpital Avicenne, APHP, Bobigny, and in private practice at Hôpital Privé de Thiais, Thiais, France. He may be reached by e‑mail at franck.fajnkuchen@avc.aphp.fr. Dr. Fajnkuchen has indicated that he has no financial disclosures in the subject matter. This article is based on data previously published in a poster that was presented at the 2012 ESCRS Congress in Milan, Italy: F. Fajnkuchen, D. Monnet, R. Nicolau, C. Temstet, G. Chaine, 1.8 mm CMICS and devices dedicated to realization of optimal capsulorhexis.

Qualities required for an optimal capsulorhexis

The capsulorhexis step is crucial during phacoemulsification. Indeed, the capsulorhexis has to follow some particular rules to warrant the best properties in the postoperative course.

A well-designed capsulorhexis will contribute to the efficient prevention of posterior capsular opacification (PCO). It also allows for optimal position of the IOL in the capsular bag and could reduce horizontal and vertical tilt. This is particularly important when using a premium IOL.

The main criteria we use to evaluate the qualities of a capsulorhexis are the size, regularity and centration of the rhexis.

An optimal capsulorhexis should have:

• A consistant diameter throughout 360°.

• A size related to the diameter of the optic of the IOL (a perfect capsulorhexis should overlap the optic by 0.5 mm to protect against contact between the anterior and the posterior capsule that may contribute to PCO).

• Good centration is mandatory.