Subluxated cataracts can be safely managed with capsular tension ring

The CTR can support the capsule in patients with damaged zonules.

Surgical management of cataract associated with zonular dialysis is a unique challenge for the ophthalmic surgeon. With recent advances in equipment and instrumentation, better surgical techniques and understanding of the fluidics, surgeons can perform relatively safe cataract surgery in the presence of compromised zonules. Implantation of a capsular tension ring (CTR) can stabilize a loose lens and allow the surgeon to complete phacoemulsification and IOL implantation.

Advantages

The use of an endocapsular flexible PMMA ring in cases of subluxated cataract, introduced by Legler and Witsciel in 1991, has changed the surgical approach to complicated situations. This technique offers four main advantages. The capsular zonular anatomical barrier is partially reformed, so that vitreous herniation to the anterior chamber during surgery is reduced or even avoided.

A taut capsular equator offers countertraction for all traction maneuvers, making them easier to perform and decreasing the risk of extending the zonular dialysis. It is much safer to use the CTR to center the lens during phaco rather than afterward. Any force transmitted to the capsule is not applied directly to the adjacent zonules, but rather is distributed circumferentially to the entire zonular apparatus.

The necessary capsular support for an in-the-bag, centered implant is obtained.

The capsular bag maintains its shape and does not collapse, which can lead to proliferation and migration of epithelial cells, development of capsular fibrosis syndrome and late IOL decentration.

Designs and descriptions

CTR or endocapsular ring. Note the eyelets at the ends of the ring.

The CTR (see figure) is made of a single piece of PMMA and is available in different sizes depending on its intended use in patients with emmetropia, low or high myopia. The original CTR, with characteristic eyelets on both ends, is marketed by Morcher.

Various similar products are marketed by other companies. As a standard CTR, the 12/10-mm diameter ring (Morcher type 14) and the 13/11-mm diameter ring (Ophtec 13/11) are the most commonly used by surgeons. Morcher type 14 is for normal axial length eyes, while type 14A and 14C are for myopic eyes.

The modifications used by Morcher include two types of CTRs with iris shields (types L and G, with integrated iris shields of 60° and 90°, respectively) and two types of capsular bending rings (CBRs) designed to prevent capsular opacification (types E and F).

The ring is minimally polished to keep the edges sharp and rectangular, facilitating the creation of a sharp, discontinuous band in the equatorial capsule. A crooked islet is located at both the ring ends to prevent spearing of the capsular fornix and to facilitate manipulation during insertion.

The CBR reduces anterior capsular fibrosis and shrinkage as well as posterior capsule opacification (PCO). The ring may be useful in patients who are at high risk of developing eye complications from opacification that require Nd:YAG laser capsulotomy, in those expected to have vitreoretinal surgery and photocoagulation and in cases of pediatric cataract.

These modified versions incorporate fixation elements that allow the surgeon to suture the ring to the scleral wall through the ciliary sulcus without violating the capsular ring.

Suturing in severe zonular dehiscence

In cases in which severe or progressive zonular dehiscence is present, implantation of the CTR alone may not be adequate. This may lead to severe postop capsular bag shrinkage as well as IOL decentration and pseudo-phakodonesis. Also, complete luxation of the bag along with the CTR and the IOL cannot be excluded.

A modified design developed by Robert Cionni, MD, with a fixation hook for severe or progressive cases of zonular deficiency solves this problem. The hook is kept opposite from the meridian of decentration and is pulled peripherally using a transscleral fixation suture to counteract capsular bag decentration and tilt.

In severe cases, two such rings or the two-hooked model can be used. However, the Cionni ring has its limitations, like difficulty of implantation if the capsulorrhexis is small. In such cases the hook may even drag on the edge of the anterior capsule, and as the fixation plane is anterior to the anterior capsule, it may cause iris chafing, leading to pigment dispersion and chronic uveitis.

An alternative is to fix the ring by guiding the needle of the scleral suture through the equator of the capsular bag, just inside the CTR. This technique has to be completed as a one-step procedure, because the suture may cut through both capsules and divide along the equator.

Another alternative in cases of severe decentration is to make a small equatorial capsulorrhexis through which a standard CTR can be inserted. A scleral suture can then be passed around the exposed CTR, which is then used to center the lens before capsulorrhexis.

Indications

The CTR is indicated for use in all cases of subluxation of the lens (see table), ranging from common cases like traumatic displacement (mechanical or surgical), Marfan's syndrome, pseudoexfoliation syndrome and hypermature cataract to rare cases like aniridia and intraocular tumors.

The best surgical technique for removing the subluxated cataract depends on the extent of the zonular dialysis. With a zonular defect of less than 90° (3 clock hours), endocapsular phaco with in-the-bag IOL implantation can be accomplished. The haptics of the IOL should be placed in the meridian of the zonular dialysis.

When the zonular tear exceeds 90°, all tractional surgical maneuvers are difficult and increase the chance of further zonular disinsertion. Moreover, the defect in the capsular-zonular barrier allows hydration and herniation of the vitreous into the anterior chamber during surgery.

Further, insufficient capsular support may make necessary either the suturing of at least one haptic of a posterior chamber IOL or the placement of an anterior chamber IOL.

Endocapsular introduction of a flexible PMMA ring has changed the surgical management of such cases, allowing safe aspiration of lens material and implantation of an in-the-bag IOL.

Applications

There are a number of indications for use of the CTR.

The efficacy of the CTR in managing zonular dialysis has been demonstrated in vitro depending on where the zonular defect presents. The CTR may be inserted during a cataract procedure. By re-establishing the capsule's contour, the CTR protects the capsular fornix from being aspirated, thereby avoiding consecutive zonular dialysis extension, irrigation fluid from running behind the capsular diaphragm with the posterior capsule bulging and vitreous prolapse into the anterior chamber with possible aspiration. With existing zonular defects such as those caused by blunt trauma, the CTR is inserted before phaco is started.

Ocular and systemic conditions may result in a zonular weakness that may be profound and progressive. Pseudoexfoliation syndrome with or without glaucoma and Marfan's syndrome are the most common causes. If zonular weakness is profound, the CTR is implanted before the cataract is emulsified and a 10-0 nylon anchoring suture may be temporarily threaded through the eyelets to remove the CTR if the zonules fail during surgery.

In pseudoexfoliation syndrome, the anterior capsule may contract excessively after in-the-bag IOL placement (capsular phimosis). This can be prevented by providing a locking mechanism that would prevent the eyelets from overlapping, suturing together the two eyelets or by using two larger implants. This can be supplemented by meticulously polishing the anterior capsule leaf overlapping the implant.

In Marfan's syndrome, some zonules may be disintegrated or elongated while the remaining ones may be still functional, giving rise to lens decentration, which may be progressive. In case of Weil-Marchesani syndrome, microspherophakia and zonular degeneration may occur. Secondary scleral suturing to remedy IOL decentration and tilt may be useful in such cases.

Use of prolonged silicone oil tamponade may lead to progressive zonular atrophy and emulsified oil or oil bubbles gaining access into the anterior chamber spontaneously or during the cataract surgery. In such cases, a large CTR should be implanted before phaco is done.

Technique

Anesthesia. Both general and peribulbar anesthesia are suitable for creation of scleral windows and trans-scleral suturing of the capsular ring or of the IOL if necessary. Special mention is required about 1% intracameral lidocaine. There is a risk of its passage through the zones lacking zonular fibers and transitory loss of sight resulting from retinal toxicity, as described in cases of capsular rupture.

Incisions. The first step is to make an incision in the eye. A needle with viscoelastic is injected inside the eye in the area where the second site is made (figure 2). This will distend the eye so that when a clear corneal incision is made, the eye will be tense and a good valve can be created. A straight rod is used to stabilize the eye with the left hand. With the right hand the clear corneal incision (figure 3).

Eye with subluxated cataract. Needle with viscoelastic entering the eye to inject the viscoelastic. This gives an entry into the eye through which a straight rod can be passed to stabilize the eye. Note no forceps holds the eye. Note also the subluxation seen to the right. Clear corneal incision. Note the straight rod inside the eye in the left hand. The right hand is performing the clear corneal incision. This is a temporal incision and the surgeon is sitting temporally. Capsulorrhexis being performed with a needle. The Ophtec injector for the CTR. Note the hook at the end of the injector. The hook of the injector locks onto the eyelet of the CTR. The capsular tension ring is withdrawn into the injector. The CTR is then inserted inside the capsular bag by the injector.

Capsulorrhexis. Commencing capsulorrhexis (figure 4) is difficult because of capsular instability. It is better to begin in the area where the zonules are whole and where the capsule offers sufficient resistance. If vitreous is present in the anterior chamber, the gel must be first isolated and vitrectomy should be performed if required. After the vitreous has been removed from the anterior chamber, a viscoelastic, preferably dispersive, is inserted by first covering the zone. Capsulorrhexis can be performed after the zone of zonular dehiscence and iridocrystalline diaphragm have been stabilized.

Hydrodissection-hydrodelineation. Hydromaneuvers should be performed meticulously to ensure correct freeing of the lens nucleus. The hydrodissection cannula should be inserted in the direction of the zone of disinsertion rather than in the opposite direction, which would enlarge the disinsertion. Viscoelastic may be required to separate the nucleus and cortical material and also to separate the cortex from the lens capsule.

Capsular ring implantation. Most CTRs can be easily inserted in the capsular bag if it is well expanded with viscoelastic. The instruments used to implant CTRs include Kelman-McPherson type forceps, special injectors marketed by Ophtec and Geuder, suitable for both Ophtec and Morcher CTRs and the one developed by Menapace and Nishi for use with CBR, and finally a guiding suture.

Figure 5 shows the Ophtec injector. This contains a small hook that attaches onto the eyelets of the CTR. The injector is brought close to the eyelet of the CTR (figure 6), and once the hook locks onto the eyelet, the plunger of the injector is released, which makes the CTR move into the injector (figure 7). Then the CTR is inserted by the injector into the capsular bag through the rhexis (figure 8).

Phaco. Nuclear phaco can be performed (figure 9) in or out of the bag, depending on the surgeon's preference. In general, phaco in these situations may be considered a safe proposition if performed properly.

Cortical aspiration. When performing automated aspiration (figure 10), movements of the tip should not be radial because of the risk of traction on the ring and the capsular bag.

IOL implantation. It is desirable to implant a larger diameter lens to minimize symptoms if lens decentration were to occur. The foldable lens (figure 11) is loaded and implanted in the capsular bag (figure 12) followed by viscoelastic removal. In either case, rotational maneuvers must be avoided or minimized.

Figure 13 shows the first postop day photograph of the same patient. Figure 14 shows the postop photograph of another patient in whom a STAAR plate haptic foldable IOL was implanted with the CTR.

Phacoemulsification performed. Cortical aspiration. Note the straight rod in left hand that helps control the movements of the eye. Allergan foldable IOL in the Unfolder. Foldable IOL in capsular bag. Viscoelastic removed with the irrigation/aspiration probe. CTR and the Allergan foldable IOL in the bag, one day postop. CTR and a STAAR plate haptic foldable IOL in the capsular bag. Note the eyelets seen clearly in the capsular bag.

Key points

Follow these key points when using CTRs:

Use a high-viscosity viscoelastic.

Make the incision at a meridian with no zonular dialysis, to avoid damage to zonular fibers with movement of the phaco tip.

Perform slow-motion phaco, with low flow rate, low vacuum and low infusion bottle height.

Emulsification can be done in the bag when the nucleus is soft and in the anterior chamber if the nucleus is hard, thus avoiding as much stress as possible to the already damaged zonular apparatus.

Perform a careful two-port anterior vitrectomy with lax infusion bottle and low aspiration pressure when necessary.

Try to place IOL haptics in the meridian of the zonular disinsertion.

Check IOL stability at the end of the surgery, both in the frontal and saggital plane, in order to consider if suturing one haptic to the sulcus is necessary.

Special conditions

Coloboma shield for large sector iris defects or iridodialysis. A tinted CTR with an integrated 60° to 90° sector shield designed by Rasch can be used to protect against glare and/or monocular diplopia (Morcher types L and G). The CTR can be placed to cover sector iris defects and/or coloboma. If more than 90° of defect is present, then more than one CTR can be used.

Multisegmented coloboma ring for aniridia. This multisegmented ring (Morcher type 50 C) is used in combination with one of the same type so the spaces in the first ring are covered by the sector shields of the second, forming a continuous artificial iris.

Anterior eye wall resection for uveal melanoma or other intraocular malignancy. The combined use of a standard and coloboma CTR is advocated in cataract surgery after anterior eye wall resection for intraocular malignancy such as uveal melanoma. Uveal tumors involving the anterior segment of the eye may need uveal resection, resulting in large iris coloboma and zonular dehiscence.

The crystalline lens may be cataractous or may become opaque after surgery of the tumor, requiring its eventual removal. For technical approach, intracapsular cataract extraction was considered previously, but the combined use of a standard and coloboma CTR may help preserve the capsular bag and cover the iris defects.

Along with primary posterior capsulorrhexis. For existing central capsule fibrosis or as a general preventive measure against capsule opacification, using a CTR has been advocated. As the CTR is in place, vector forces during primary posterior capsulorrhexis can be controlled in a better way as the ring stretches the posterior capsule, giving uniform radial vector forces. As the CTR is in place, distortion in shape of the primary posterior capsulorrhexis can be avoided, and folds on the capsule caused by traction due to oversized and rigid lens loops can be prevented. This allows closer and perfect apposition of the posterior capsule with the optic of the IOL, preventing lens epithelial cells from entering the retrolental space in the posterior capsulorrhexis margin and thus preventing the secondary primary posterior capsulorrhexis closure.

In combined cataract and vitreous surgery. When the CTR is in place, the posterior capsule remains uniformly distended and a perfect peripheral view is possible. Also, as the CTR is in place, silicone oil can be removed through the same phaco incision from the primary posterior capsulorrhexis, which can be performed in a controlled manner with the CTR in place.

As a tool to measure capsular bag circumference. The CTR in vivo can be visualized gonioscopically from a well dilated pupil. The distance between the eyelets can be determined by adjusting the width of the slit beam of the slit lamp to fill in the space between the eyelets that can be read directly on the slit lamp. This capsular bag biometry can be used for quantifying in vivo capsular bag circumference and capsular bag shrinkage dynamics.

For prevention of posterior capsular opacification. Theoretically, the smaller the space between the lens optic and the posterior capsule, the lesser the chances of lens epithelial cells migrating behind the optic (ie, no space, no cells). When the CBR is in place, this space is less common, and if present is less in amount than without a CBR.

Also, by keeping the anterior capsule away from the posterior capsule, myofibroblastic transdifferentiation of lens epithelial cells on the anterior capsule edge and back surface can be prevented. The CBR is an open, band-shaped PMMA ring 11 mm in diameter and 0.2 mm thick with pretension (13 mm diameter when open and 0.7 mm thick).

For Your Information:

• The authors, staff members of Dr. Agarwal's group of eye hospitals in Chennai (India), Bangalore (India), and Dubai (UAE), can be reached at Dr. Agarwal's Eye Hospital, 19 Cathedral Road, Chennai-600086, India; (91) 44-811-6233/811-5871; fax: (91) 44-811-5871; e-mail: dragarwal@vsnl.com. The authors have no direct financial interest in the products mentioned in this article, nor are they paid consultants for any companies mentioned.

• Morcher GmbH can be reached at Kapuzinerweg 12, 70374 Stuttgart, Germany; (49) 711-95320-0; fax: (49) 711-95320-80; e-mail: info@morcher.com.

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