Presbyopia / SPO - 3.2.3.4. Routine use of capsular tension rings in crystalline lens surgery

3.2.3.4. Routine use of capsular tension rings in crystalline lens surgery with premium lens implant: Yes or no?

Manuel Tavares Correia 1, Isabel Prieto 2.

1 - Hospital Narciso Ferreira - Irmandade Da Santa Casa Da Misericórdia De Riba De Ave, Portugal

2 - Hospital Prof. Dr. Fernando Fonseca EPE, Amadora, Portugal

INTRODUCTION

Capsular Tension Rings (CTR) are medical devices made of open-loop, closed-ring, or ring-segment-only polymethyl methacrylate (PMMA), with holes in the ends, with or without changes to facilitate suturing and which are intended to be introduced into the capsular sac and left there permanently for various purposes. The first published papers on their use (Legler¹ and Nagamoto²) date from 1994 and have since become a key tool for improving cataract surgery outcomes, not only in facilitating surgery in cases of weakness or sectoral absence of the zonule, but also, in the long term, for helping to keep the complex bag/lens centered. This contributes to better visual quality, which is essential in the case of multifocal lenses, where a slight off-center lens has disastrous consequences on the patient's visual quality. They also facilitate suturing the bag/lens complex to the sclera in the event of subluxation or dislocation.

MECANISMS OF ACTION

In this chapter only the simple (conventional) open rings will be analyzed, which are the ones that can be used in a “prophylactic” manner to maintain visual quality over time in the case of “premium” IOL implantation, to measure whether it may or may not be worth to routinely implant a capsular tension ring into a healthy bag during cataract lens surgery. Its shape and consistency make it act as a spring inside the capsular bag, distending it and producing the making that^3,4:

There is an increase of the centrifugal force of the zonule;
There is capsular stabilization during phacoemulsification;
There is a distribution of forces throughout the 360° of the capsular bag, very useful in cases of weakness or sectoral absence of the zonule (e.g. high myopia, pseudo-exfoliation, trauma);
The anterior capsule remains stretched, with studies indicating that CTR inhibits the migration of epithelial cells in the anterior capsule and consequently the risk of capsular contraction and phimosis (e.g. pseudo-exfoliation, retinitis pigmentosa);
The posterior capsule remains stretched, which reduces the occurrence of folds as well as cell proliferation in its opacification (PCO)^5-7;
Increasing the rigidity of the bag, which coupled with the force distribution at 360°, makes the bag-lens complex tilt less likely, improving intraocular lens centration (better visual quality, especially in multifocal IOLs)¹⁰.

IMPLANTATION TECHNIQUE

There are several manual or injector-assisted techniques for deploying CTRs. However, the one-hand technique, with rotation of the ring along the equator of the capsular bag, as it is implanted, causes friction on the same, which induces some traction on the zonula, which may rupture its fibers, and if the bag is not well filled with surgical viscoelastic material and the capsule has folds, it may also puncture it and migrate to the vitreous, compromising surgery. The CTRs can be implanted manually, by incisions smaller than 1 mm (through the main incision or paracenteses) or with the aid of an injector, requiring incisions larger than 1.8 mm.

Among the various techniques described for implanting CTRs (Figure 1), the two-handed injector-assisted CTR is preferable: one hand holds the injector, which will be introduced through the main incision, and the other one holds a hook through a paracentesis.

Figure 1. CTR as it exits from its packing. It must be collected in the injector to implant itself.

Figure 2. Inserting the hook into the distal opening of the CTR. Note the lateralized position of the tip of the injector and not in the center of the rhexis.

Figure 3. As it is deployed, a loop forms.

Figure 4. The end is released distal to the CTR by rubbing it on the injector end.

Figure 5. Finally, the proximal end of the CTR is released, controlled by the hook.

As the CTR begins to be injected, the tip of the hook is inserted into the distal opening of the CTR (Figure 2) remaining near the injector end and holding the ring, which causes it to enter the anterior chamber forming a loop that should be placed under the capsulorhexis (Figure 3). When the CTR is almost fully implanted, it releases from the hook with a small frictional movement against the injector tip (Figure 4). Then, when the proximal opening of the CTR emerges at the tip of the injector, it releases from the piston that pushes it with the help of the hook (Figure 5). In this way, the first part of the ring to enter the capsular bag is its central part and only after the ends, which prevents rotation and consequent friction in the capsular equator, giving a greater degree of certainty of that is deployed to the proper location.

An appropriately sized ring should be implanted into the bag. Thus, Morcher, manufacturer of CTRs, proposes to choose the CTR according to the “white-to-white” size, or the axial length of the eye, as shown below:

Table 1. CTR to be implanted according to the “white-to-white” size of the eye

Table 2. CTR to be implanted according to the axial length of the eye

CONTRAINDICATIONS OF CTR IMPLANTATION

The CTRs are contraindicated in cases of3:

Incomplete capsulorhexis because of the danger of radial rupture extension to the posterior capsule;
Posterior capsule rupture, due to the possibility of increased rupture, or dislocation to the vitreous cavity;
Small eyes, with narrow chamber angles, as they may cause an angle closure and, consequently, acute glaucoma;
Use of plate lenses without fenestration, as they may cause an IOL dislocation to the anterior chamber;
Extreme zonular weakness, with excessive bag mobility, due to the risk of dislocation to the vitreous chamber, this possibility may be less likely if the implant is performed using the technique described above.

DISCUSSION

We should only use a technique if the advantages presented far outweigh the disadvantages. In relation to the use of capsular tension ring in lens surgery with implant of “Premium IOLs” the advantages are:

What is gained?

A higher positional predictability of the IOL, bearing in mind that there may be under correction of about 0.50 D, as the IOL tends to assume a more posterior position2;
Less likelihood of anterior capsular contraction4: less cell proliferation in the posterior capsule and consequently less need for YAG laser capsulotomy5-7;
A lower possibility of folds in the posterior capsule, with its implication in visual quality5-7;
Easier IOL exchange if necessary (biometric error, inadaptation to multifocality, or other) or repositioning it inside the bag (toric lenses off the intended axis);
Easier repositioning of the IOL-bag complex by suture in the case of decentration due to sub-dislocation/dislocation3.

What is lost?

Poor positioning (which can lead to IOL decentration or inclination to UGH Syndrome), posterior capsule rupture or “leak” in capsulorhexis due to poor surgical technique;
Increased surgical time;
Ring cost.

CONCLUSION

With proper technique, implanting a capsular tension rings into the capsular bag is very safe. The advantages of their use in routine cases are not absolute because they are not fully effective in preventing postoperative complications8,9,11. However, as its price is not high, and it has a positive influence on the reduction of postoperative complications, we are of the opinion that it is an asset and should be used routinely, at least in cases of “premium IOL implantation”, in which small details, such as IOL decentration, can have a huge impact on patients' visual quality. Biometrics may need to be measured in the case of CTR implantation, since the effective position of the IOL may be a little posterior, which hypo-corrects the eye12.

REFERENCES

Legler UF, Witschel BM. The capsular ring: A new device for compli-cated cataract surgery. German J Ophthalmol 1994; 3: 265
Nagamoto T, Bissen-Miyajima H. A ring to support the capsular bag after continuous curvilinear capsulorhexis. J Cataract Refract Surg 1994; 20(4): 417–20.
Moreno-Montanés J, Caire JM. Anillos endosacularesen la cirúgia de cataratas. Madrid: Sociedad Espanola de de Oftalmologia 2008; 518-28.
David Andreu Andreu. Anillos de tensión capsular: Cómo, cuándo y posibles complicaciones. Monografia SECOIR nº 18, 2017; 207-15.
Hara T, Hara T, Hara T. Preventing posterior capsular opacificatio with an endocapsular equator ring in a young human eye: 2-year follo-w-up. Arch Ophthalmol 2007; 125(4): 483–6.
Menapace R, Sacu S, Georgopoulos M, Findl O, Rainer G, Nishi O. Efficacy and safety of capsular bending ring implantation to prevent posterior capsule opacification: Three-year results of a randomized cli-nical trial. J Cataract Refract Surg 2008; 34(8): 1318–28.
Kim JH, Kim H, Joo CK. The effect of capsular tension ring on pos-terior capsular opacity in cataract surgery. Korean J Ophthalmol 2005; 19(1): 23–8.
Scherer M, Bertelmann E, Rieck P. Late spontaneous in-the-bag in-traocular lens and capsular tension ring dislocation in pseudoexfolia-tion syndrome. J Cataract Refract Surg 2006; 32(4): 672-5.
Ahmed IIK, Chen SH, Kranemann C, Wong DT. Surgical reposi-tioning of dislocated capsular tension rings. Ophthalmology 2005; 112(10): 1725-33.
Lee DH, Shin SC, Joo CK. Effect of the capsular tension ring on in-traocular lens decentration and tilting after cataract surgery. J Cataract Refract Surg 2002; 28(5): 843-6.
Oner FH, Kocak N, Saatci AO. Dislocation of the capsular bag with intraocular lens and capsular tension ring. J Cataract Refract Surg 2006; 32(10): 1756-8.
Park HJ, Lee H, Kim do W, Kim EK, Seo KY, Kim TI. Effect of Co-Implantation of a Capsular Tension Ring on Clinical Outcomes after Cataract Surgery with Monofocal Intraocular Lens Implanta-tion. Yonsei Med J 2016; 57(5): 1236-42.

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