CAPSULAR TENSION SEGMENT TECHNIQUE FOR IOL FIXATION AND CENTRATION

Seng-Ei Ti, FRCS(Ed), MMed(S’pore) and Soon-Phaik Chee, FRCOphth, FRCS(G), FRCS(Ed), MMed(S’pore)

Subluxated intraocular lenses (IOLs) may occur as an early or delayed complication of cataract extraction with IOL implantation due to lack of support of the capsular bag caused by weak and absent zonules. Early-onset IOL subluxation may be the result of inadequately addressed zonulopathy at the initial surgery or an IOL placement lacking stability, such as may occur following a posterior capsule rupture. Delayed-onset IOL subluxation¹ may be associated with ocular trauma, which includes chronic rubbing in the atopic individual, progression of zonular disease (eg, pseudoexfoliation or Marfan syndrome), or chronic inflammatory diseases such as uveitis and retinitis pigmentosa. However, in many cases, no such history is obtained and it appears to be idiopathic.²

Approach to the Subluxated IOL

When planning surgery, several factors should be considered.

• Whether the IOL is accessible from an anterior segment approach or whether surgery should be combined with a vitreoretinal surgeon.
  
• Whether the same IOL can be reused for fixation or whether an IOL exchange is needed. This depends on the IOL design and the fixation technique.
  
• The status of the capsular bag relative to the IOL (ie, absence or presence of bag, integrity [intactness], and whether the capsular bag can be reinflated). In the instance where the bag is intact and inflatable, a capsule stabilization device may be inserted for scleral fixation.

Other surgical factors to consider include the following:

• Cause of subluxation if recurrent (eg, eye rubbing)
  
• IOL power—IOL exchange if diopter change is desired
  
• IOL type (eg, multifocal or monofocal)
  
• Need for triamcinolone acetonide–assisted dissociated anterior vitrectomy
  
• Corneal endothelial status—Possibility of future endothelial keratoplasty, if presenting endothelial cell counts are very low (eg, < 1000 cell/mm²)
  
• Retinal status—Macular pathology and retinal breaks
  
• Previous surgery (eg, filtration or seton surgery, scleral buckle causing conjunctival scarring and adhesion or vitrectomy)

Finally, considering all the above factors, one should determine the method of IOL fixation. The IOL may be fixated to the sclera or iris, with sutures or without.

IOL Fixation Techniques

Iris fixation³ is a simple, conjunctival-sparing, minimally invasive, and quick technique that the authors favor. It is suitable in most eyes and is the first option to consider. However, it requires that the iris is not diseased and the pupil is round and centered. This technique should generally be avoided in the uveitic eye, in the presence of traumatic iridodialysis, or if there is loss of iris tissue. Iris fixation may be done with polypropylene sutures (modified Siepser knot^4,5 or McCannel suture) or sutureless (ie, exchanging subluxated IOL for an iris clip IOL placed in the retropupillary plane).6

When trans pars plana vitrectomy has been performed, iris-fixated IOLs become excessively mobile. In such cases, fixation to the sclera is preferred. In the past, the suturing of a single-piece polymethylmethacrylate (PMMA) IOL with 6-mm optics specially designed for scleral fixation was widely practiced. However, the universally used 10-0 polypropylene suture initially thought to be a permanent suture was subsequently found to have a clinical lifespan of 7 to 8 years, resulting in resubluxation of the IOL.⁷ As such, many authors have transitioned to using polypropylene 9-0 or Gore-Tex 7-0 (polytetrafluoroethylene CV-8; WL Gore & Associates; off-label use) sutures with the hope that these can last a lifetime, especially in pediatric eyes. In the effort to keep the incision small, foldable IOLs with loop haptics, such as the Akreos Adapt AO (Bausch + Lomb) have become popular among vitreoretinal surgeons, who conveniently place the sutures via the sclerotomy ports.

In recent years, intrascleral haptic fixation techniques with or without glue have been gaining favor,⁸ obviating the need for suture fixation. Several techniques with or without scleral flaps have been described, but all require a 3-piece IOL with haptics made of PMMA or polyvinylidene fluoride for anchoring to the sclera.

In instances where the subluxated IOL-within-the-bag is a single-piece hydrophobic acrylic IOL or single-piece platehaptic IOL, iris fixation and intrascleral fixation are not possible, necessitating an IOL exchange.

The use of toric, multifocal, or multifocal toric IOLs is increasing. These IOLs are rarely found in a 3-piece IOL configuration for reasons of refractive stability and centration over the short and long term. In particular, if the fellow eye has also been implanted with a similar IOL, patients with subluxated premium IOLs often wish to maintain their original premium IOL. The authors’ preferred technique for this situation is to insert a capsule stabilizing device, such as the Ahmed capsular tension segment (CTS; Type 6E, Morcher GmbH)⁹ or AssiAnchor (Hanita Lenses),¹⁰ into the capsular bag and to then anchor it to the sclera. Currently, there are no sutureless capsule anchoring devices commercially available. Some authors have also described a direct suturing technique, such as looping the scleral suture around the haptic with or without a preexisting capsular tension ring through the capsular bag.¹¹ Alternatively, one can directly suture the fibrosed capsular rim¹² or suture through the IOL optic or haptic. However, although direct suturing techniques are appropriate for a monofocal IOL, it is difficult to adjust the IOL position for multifocal centration and toric alignment after the suture has been passed through the bag and sclera. This chapter describes the authors’ surgical approach using a CTS to stabilize a subluxated toric, multifocal, or multifocal toric IOL within the capsular bag. Being able to shift a capsular stabilizing device within the bag facilitates more accurate alignment of premium refractive IOLs.

Historical Perspective

In 2002, Dr. Ike Ahmed designed the CTS Type 6E, a PMMA partial ring, with an arc length spanning 120 degrees. The CTS has a raised single eyelet centrally for suturing to the sclera, and is designed to sit anterior to the anterior capsule.⁹ A double eyelet modification (CTS Type 9L; Morcher GmbH) for stabilizing a wider span of the capsular bag has been designed, but currently is not commercially available. The CTS is indicated for a zonular dialysis greater than 4 clock hours and can be placed even in the presence of an anterior or posterior capsule tear. Because its arc length is short, no dialing technique is needed during insertion and more than one device may be implanted. It should be placed within the capsular bag at the location of greatest zonular weakness where the central eyelet remains in front of the anterior capsule and can be supported by an iris retractor.

In 2006, Richard Hoffman et al published their technique of creating a partial-thickness scleral pocket without conjunctival dissection for scleral fixation.¹³ The sclera dissection is initiated from a peripheral clear corneal incision followed by full-thickness passage of a double-armed suture through the scleral pocket and conjunctiva. The suture ends are retrieved from the pocket and tied.

Our Surgical Technique

Our current IOL-capsular bag scleral fixation technique uses the CTS and Hoffman pocket principles (Figures 9-1 and 9-2). The CTS suture externalization technique has been modified to effectively reduce the number of needles entering the eye. See Video 9-1 on the management of subluxated multifocal toric IOL in a post-vitrectomy eye.

In the earlier reported ab externo technique,¹⁴ a bent half-inch 27-gauge or larger bore needle is passed full-thickness through the scleral pocket using one hand, and with the other hand, the needle of the one end of the double-armed suture bearing the CTS is railroaded in. The external needle is withdrawn from the eye, retrieving the suture with it. The other end of the double-armed suture is similarly retrieved. Alternatively, an ab interno technique may be used, whereby the needle is passed from within the eye through the scleral pocket at the desired scleral fixation point. For both techniques, the desired suture fixation point is 1.75 mm posterior to the limbus. The needle used for 9-0 polypropylene sutures may either be curved or straight, but for Gore-Tex 7-0, the large thick needle will need to be straightened to be used.

We prefer Gore-Tex 7-0 suture because it handles well and is robust and our modified technique dispenses with the needle. A short length of the Gore-Tex suture is threaded through a 26-gauge needle to create a suture snare to retrieve the Gore-Tex suture bearing the CTS to the scleral fixation site.

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