Utilization of the Cionni MCTR

Modern cataract surgery generally provides excellent visual outcomes. However, in cases with poor capsular support, the potential for complication is significantly increased. Capsular tension rings (CTRs), modified capsular tension rings (MCTRs), and capsular tension segments (CTSs) have been developed to facilitate small-incision phacoemulsification and in-the-bag implantation of a posterior chamber intraocular lens (PC IOL) when the zonules are deficient. These capsular support devices have truly revolutionized our approach to zonular dialysis.

Indications

For cases involving less than 4 clock hours of zonular dialysis, a standard CTR is usually suitable. Introduced for this purpose by Legler and Witschel in 1993, the CTR is an open-ended, flexible, horseshoe-shaped polymethylmethacrylate (PMMA) filament with 2 eyelets at either end.^1,2 Once inserted into the capsular bag, the CTR places centrifugal forces against the entire capsular equator, and, by recruiting strength from the stronger zonules, the CTR supports the compromised areas of the capsular bag. The effect is a dramatic expansion and stabilization of the capsular bag.

In cases of more significant zonular dialysis (ie, greater than 4 clock hours) or considerable decentration of the lens, a standard CTR may not provide adequate centration or stability. Additionally, long-term centration in patients with progressive generalized zonular weakness, such as that caused by pseudoexfoliation, is uncertain. There have been reported cases of complete posterior dislocation of a CTR and PC IOL within the capsular bag occurring years after the original surgery in patients with pseudoexfoliation syndrome (Ophthalmology. 2005;112(10):1725–1733.) In these cases, an MCTR (Morcher GmbH, Stuttgart, Germany) might be a better solution.^3,4

The MCTR incorporates a fixation hook that courses anteriorly and centrally in a second plane, 0.25 mm above the plane of the tension ring. The fixation hook wraps around the capsulorrhexis edge and rests on the residual anterior capsular rim. At the free end of the hook is the eyelet through which a suture can be passed and used for scleral fixation without violating capsular bag integrity (Figure 1).

Image courtesy Robert Cionni, MD.

Figure 1. MCTR 1-L.

 

There are 3 MCTR models available. Model 1-L has a single fixation hook located on the trailing end of the ring. Model 2-C has a single fixation hook located on the leading edge of the ring, allowing it to be injected into the bag using a specially designed shooter (Geuder shooter). Model 2-L has 2 fixation hooks and is used in patients with very significant generalized weakness where 2-point fixation is required (Figure 2).

Image courtesy Robert Cionni, MD.

Figure 2. MCTR models.

Like the standard ring, MCTRs of any model should not be used if a complete continuous capsulorrhexis is not attained or if a posterior capsule tear occurs, as the expansile forces of the rings will likely induce complete bag rupture. If it is not possible to place a CTR or an MCTR, the surgeon may choose to suture the IOL to the iris, scleral wall or implant an anterior chamber IOL. However, it may be possible to place a CTS in these cases, as the CTS does not induce an expansile force. The CTS is a shortened version of the MCTR, designed by Ike Ahmed, MD, in 2002 (Morcher GmbH, Stuttgart, Germany). The CTS can be used to stabilize a quadrant of zonular compromise without expanding the capsular bag circumferentially.

MCTR Implantation Technique

You can insert the MCTR anytime after completion of the capsulorrhexis. However, the presence of a large, dense nucleus makes it difficult. In addition, visualization during insertion is better if the nucleus is removed first. Therefore, we prefer first to stabilize the capsular bag using disposable nylon iris retractors placed through limbal stab incisions at the capsulorrhexis edge during phacoemulsification, and then place the ring after the nucleus has been removed (Figure 3). We leave the iris retractors in place to lend stability and countertraction during ring placement.

Image courtesy Robert Cionni, MD.

Figure 3. Use of disposable iris retractors.

Viscoelastic should be placed under the surface of the residual anterior capsular rim before inserting the MCTR. This creates a space to place the ring and to dissect any residual cortex away from the peripheral capsule, making cortical entrapment by the ring less likely.

Pre-place a 9.0 Prolene or 8.0 Gortex suture, double-armed with long needles, through the eyelet of the fixation hook before implantation. You could also use a single-armed suture and tie the free end of the suture to the fixation hook eyelet.

Insert the MCTR with smooth forceps and dial it into the capsular bag with a Y-hook. The fixation hook will often “capture” anteriorly to the capsulorrhexis edge spontaneously. If it does not, manipulate the hook anteriorly with an Osher Y-hook (Duckworth and Kent) and a Cionni nucleus manipulator (Duckworth and Kent) to retract the capsulorrhexis edge. Rotate the fixation hook to the center of the zonular weakness and displace it to the scleral wall to check bag centration (Figure 4). If the 2-hook MCTR (2-L) is used, the fixation site for each hook must be ascertained by displacing each hook to the scleral wall before suturing. Depending on the size of the capsular bag, the best centration may be obtained with the hooks less than 180° apart.

Image courtesy Robert Cionni, MD.

Figure 4. Displacing the fixation hook

Make a scleral flap at this intended suture fixation site. Inject viscoelastic between the iris and the anterior capsule to create space, and pass the needle through the incision, posterior to the iris, anterior to the anterior capsule, and out through the ciliary sulcus and scleral wall about 1.5 mm posterior to the corneal-scleral junction (Figure 5). An ab externo approach to passing the suture, as described by Alan Crandal, MD, and Ike Ahmed, MD, will eliminate a “blind pass” of the needle as it disappears under the iris (J Cataract Refract Surg. 2001;27(7):977).

Image courtesy Robert Cionni, MD.

Figure 5. Passing the needle.

Prior to removing the needle from the scleral wall, enlarge the needle tract with a 15° blade to lessen the effort required to rotate and bury the knot. Tighten the sutures just enough to achieve centration, and then tie a knot. The knot is buried in the posterior scleral bed and the conjunctiva is brought back into position over the scleral flap. If you use a single-armed suture, pass the needle partial-thickness through the scleral bed beneath the scleral flap and tie the suture to itself.

After suture fixation, aspirate the remaining cortex, reinflate the capsular bag with viscoelastic, and insert the PC IOL. We have found it easiest to insert a single-piece acrylic PC IOL into the capsular bag in these cases (Figures 6a and 6b).

Image courtesy Robert Cionni, MD.

Figure 6a. A young patient with a subluxated crystalline lens.

Image courtesy Robert Cionni, MD.

Figure 6b. Patient after MCTR placement and IOL implantation.

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If vitreous presents at any time during the procedure, it should be carefully and completely removed from the anterior chamber. Small amounts of vitreous can be removed by using a “dry” vitrectomy technique with an automated vitrector and an anterior chamber filled with viscoelastic. For significant vitreous prolapse, a bimanual vitrectomy should be performed. This is best accomplished by using a side-port incision for irrigation. The vitrectomy handpiece can be inserted through the initial incision or through a pars plana sclerotomy.

Summary and Conclusion

The management of significant zonular weakness remains challenging. However, newer surgical techniques now afford us the possibility of saving the capsular bag, recentering the capsular bag, and even placing a PC IOL within the capsular bag. This allows the surgery to be performed through a 2.2 mm incision, giving the patient a rapid and long-lasting visual recovery.

References

1.	Legler U, Witschel B, et al. The capsular tension ring: a new device for complicated cataract surgery. Paper presented at: Annual Meeting of the American Society of Cataract and Refractive Surgery (ASCRS); May 1993; Seattle, WA.
2.	Cionni R, Osher R. Endocapsular ring approach to the subluxated cataractous lens.J Cataract Refract Surg.1995;21(3):245–249.
3.	Ahmed I, Chen S, Kranemann C, Wong T. Surgical repositioning of dislocated capsular tension rings.Ophthalmology.2005;112(10):1725–1733.
4.	Cionni R, Osher R. Management of profound zonular dialysis or weakness with a new endocapsular ring designed for scleral fixation.J Cataract Refract Surg.1998;24(10):1299–1306.
5.	Cionni R, Osher R, Marques D, et al. Modified capsular tension ring for patients with congenital loss of zonular support.J Cataract Refract Surg.2003;29(9):1668–1673.
6.	Ahmed I, Crandall A. Ab externo scleral fixation of the Cionni modified capsular tension ring.J Cataract Refract Surg.2001;27(7):977.

Author Disclosure

Dr. Cionni, as its developer, has a financial interest in the modified capsular tension ring (MCTR). He is also a consultant for Alcon Laboratories, Inc.