26 Capsular Tension Devices The success of cataract surgery may be uncertain when it is threatened by the presence of zonular weakness, which increases the intraoperative risk of vitreous prolapse, capsular rupture, and retained lens material, as well as the postoperative risk of intraocular lens (IOL) dislocation. Capsular tension rings (CTRs) and related endocapsular devices enable surgeons to approach zonular weakness during complex cataract surgery with improved safety and have become a well-established tool in the armamentarium of cataract surgeons. Nagamoto and Bissen-Miyajima1,2 as well as Hara et al3,4 initially developed the capsular bag supporting ring independently in Japan around 1990. Although their original intent was for a device designed to maintain the circular contour of the capsular bag, they also created an effective new approach for managing zonular weakness. In 1993, Legler and Witschel5 were the first to present the placement of an open-ringed polymethylmethacrylate (PMMA) CTR in a human eye during cataract surgery. There are now multiple variations of this simple, innovative device and its use is widespread. The CTR is a PMMA open-ring device with blunt-tipped eyelets at its ends. A CTR can be inserted at any point during cataract surgery following creation of a strong anterior capsulotomy created via capsulorrhexis (Fig. 26.1a) or femtosecond laser (Fig. 26.2) and can serve to support the capsular bag during surgery as well as provide long-term IOL stabilization. The diameter of the open-ring is designed to be greater than that of the capsular bag when in its final position. The CTR creates an equally distributed centrifugal force to the equator of the bag. Thereby, the CTR recruits tension from stronger zonules to buttress areas of weak or absent zonules, stabilizing the entire complex. This distribution of support may re-center a mildly subluxed capsular bag, but it will not re-center a severely subluxed capsular bag nor will it cure a progressive zonulopathy. In these situations, a modified capsular tension ring (MCTR) or a capsular tension segment (CTS) provides a stable long-term solution through scleral fixation. A CTR decreases the prevalence of posterior capsule opacification (PCO) following cataract surgery.6 Whether a CTR will decrease the rate capsular contraction syndrome is still being evaluated (see below). Any cause of zonular weakness or loss may be an indication for CTR placement. The most common causes of zonular insufficiency are pseudoexfoliation syndrome, trauma, previous ocular surgery (e.g., filtering surgery or vitrectomy), hypermature cataracts, and increased axial length.7–22 Less common causes include Marfan’s syndrome, homocystinuria, Weill-Marchesani syndrome, microspherophakia, retinitis pigmentosa, and intraocular neoplasms.23–32 A full list of causes are as follows: Fig. 26.1 (a) Beginning a continuous curvilinear capsulorrhexis (CCC) with a cystotome. (b) A cystotome is used to complete the capsulorrhexis. (c) A complete CCC. (d) A dispersive viscoelastic is used to both visco-dissect and visco-lift the lens nucleus from the capsular bag. (e) Aspiration of the lens material using coaxial irrigation/aspiration. (f) Completion of lens cortex removal. (g) Preoperative photo of a subluxed crystalline lens in a patient with Marfan’s syndrome. If there exists significant decentration or phacodonesis, a standard CTR is not likely to provide adequate support. When these conditions exist, a scleral fixation CTR design provides better long-term centration and stabilization. A contraindication to the use of a CTR is an anterior or posterior capsular tear. In the setting of a noncontinuous capsular tear, the centrifugal force generated by the ring may cause tear extension and risk loss of the CTR to the posterior segment.33 It may be possible to utilize a CTS in these cases.13,14 Fig. 26.2 Femtosecond laser creation of anterior capsulotomy; note the area of traumatic zonular dialysis. The general structure and mechanics of the standard CTR are discussed above. Both Morcher (Stuttgart, Germany) and Ophtec (Groningen, The Netherlands) manufacture CTRs that are approved by the United States Food and Drug Administration (FDA). The Morcher ring is currently distributed in the United States by FCI Ophthalmics (Pembroke, MA) and Alcon Laboratories, Inc. (Fort Worth, TX), and is available in three sizes: 12.3 mm (compresses to 10.0 mm), 13.0 mm (compresses to 11.0 mm), and 14.5 mm (compresses to 12.0 mm). The Ophtec ring is distributed in the United States by Abbott Medical Optics (Irvine, CA) and is available in a 13-mm ring (compresses to 11 mm) and a 12.0-mm ring (compresses to 10.0 mm). Insertion of the ring can be accomplished manually with forceps or by using an injector. All of the above rings are also available in a preloaded, single-use injector, which is our preferred method of insertion. Geuder (Heidelberg, Germany) and Ophtec make reusable injectors designed for one-handed implantation of the CTRs; Ophtec CTRs are not compatible with the Geuder injector. A modification of the standard CTR design is the Henderson Ring,34 which features eight equally spaced indentations spanning the circumference of the ring creating a sinusoidal shape. The indentations enable nuclear and cortical material removal while still maintaining the desired stretch of the capsular bag. Capsular bag dimensions dictate the size of CTR selected. Overlap of the terminal eyelets is required for maximum circumferential support. As shown by Vass et al35 and others,36 the size of the capsular bag correlates with globe axial length and corneal diameter. As such, horizontal white-to-white and axial length measurements should guide a surgeon’s CTR selection. Using a larger CTR ensures overlap of the end terminals but may be more challenging to insert. The modified capsular tension ring37 was developed as a solution to profound zonular insufficiency (Fig. 26.1g) allowing surgeons to anchor an intact capsular bag to the scleral wall. As with the standard CTR, the MCTR utilizes a PMMA open-ring design, but, unlike the standard CTR, there are one or two fixation eyelets attached to the ring, which enable it to be sutured to the sclera (Fig 26.3 a). The eyelets protrude 0.25 mm forward from the ring of the CTR and sit anterior to the anterior capsule. A more recent modification designed by Boris Malyugin38 incorporates a pigtail curve at the terminus of one end of the ring such that the fixation eyelet rests at a plane anterior to the plane of the remainder of the ring. This design enables insertion with an injector (Figs. 26.5a,b). An adequately sized capsulotomy (5–6.5 mm) is desired to ensure safe removal of the cataract, stable positioning of the ring, and proper interface of the hook of the MCTR eyelet with the capsulorrhexis margin (Fig. 26.3,4,6).13 Similar to the MCTR, the CTS was also created for patients with extensive and/or progressive zonular loss.13,14 The partial PMMA ring segment spans a 120-degree arc with a radius of 4.5 or 5 mm and with an anteriorly positioned fixation eyelet. Unlike the CTR and MCTR, the CTS can be utilized in cases where a discontinuous capsulorrhexis, anterior capsule tear, or a posterior capsule tear is present, as it does not generate a 360-degree expansile force. Multiple CTSs can be used when necessary. The CTS provides support in the transverse plane, and must be combined with a CTR or MCTR when circumferential support is required. The CTS may also be used for intraoperative support and removed prior to completion of the case. The CTS is available in two different radii of curvature: 4.5 mm (model 6E) and 5.0 mm (model 6D). The choice of the capsular tension device in a particular situation depends on the cause of capsular bag instability as well as surgeon comfort and preference regarding the available device options. Progressive zonular disorders (e.g., pseudoexfoliation, Marfan’s syndrome) should be thought of as separate from nonprogressive zonular defects (e.g., prior trauma, iatrogenic). One must also consider the amount of zonular loss or generalized zonular instability. Fig. 26.3 (a) Passing a CV-8 expanded polytetrafluoroethylene suture through the fixation eyelet of the modified capsular tension ring (MCTR). (b) Manual insertion of the MCTR into the capsular bag. (c) Continuation of manual insertion of the MCTR, using a second instrument to guide the placement of the ring. (d) Continuation of manual insertion. (e) The MCTR within the capsular bag after dialing into position for fixation. In cases where the remaining zonules are expected to be strong, a standard CTR may enable adequate redistribution of zonular force, compensating for an area of zonular weakness or dialysis.7,11,12,15 More generally, CTRs are indicated in cases of mild, diffuse zonular weakness or small, localized zonular dialysis (generally less than 4 clock hour positions). In more advanced or progressive zonulopathies, a scleral-fixated MCTR or CTS paired with a CTR likely provides the best long-term solution.13,37,39–42 The timing of placement may also dictate the type of device used. Early ring placement provides capsular distention to prevent capsular bag collapse during phacoemulsification or cortex aspiration.7,10 Placement of a CTR or MCTR requires the device to be dialed into position, which may require more manipulation prior to or during phacoemulsification and thus cause zonular trauma. Ahmed et al43 demonstrated that early CTR placement leads to greater zonular stress and iatrogenic zonular trauma when compared with CTR placement after cataract and cortex removal. Early ring placement also makes cortex removal difficult. If early placement is necessary, one might consider a Henderson CTR or a CTS to provide greater ease of aspiration of cortex. In addition, a CTS can be placed relatively atraumatically on account of its smaller size, requiring less manipulation for adequate positioning. In the setting of an anterior or posterior capsular tear, which are contraindications to the use of a CTR or MCTR, a CTS can be used due its transverse force rather than circumferential force. As stated above, it is our preference to utilize single-use injectors with a preloaded CTR. If there is worry that the insertion of the CTR will exacerbate existing zonular damage, over-bending the ring during insertion by providing countertraction with a suture or second instrument can provide a more gentle insertion (Fig. 26.4a–d). When a case requires placement of an MCTR, it is our current preference to inject a preloaded Morcher-type 10 L 9 (based on the Malyugin Design) pre-loaded with suture (Fig. 26.5a,b). An alternative method is to insert, by hand, a standard Cionni Modified CTR. Our method for scleral fixation is a variation of an ab externo technique previously described by Slade et al44 (Fig. 26.3, and 26.6). This technique uses a micro-vitreoretinal blade to create sclerotomies and an internal limiting membrane forceps or Condon Snare (MicroSurgical Technology, Redmond, WA) to retrieve a CV-8 expanded polytetrauoroethylene (Gore-Tex, not labeled for ophthalmic use) or 9-0 polypropylene suture pre-passed through the eyelet of the MCTR (Fig. 26.6a). This same method of fixation is also our preference for CTS fixation.
Mechanics of Capsular Tension Rings
Patient Evaluation: Indications and Contradictions
Device Types
Standard Capsular Tension Ring
Selecting Capsular Tension Ring Size
Modified Capsular Tension Ring
Capsular Tension Segment
Choice of Device and Timing of Placement
Method of Insertion
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