CAPSULAR ANCHOR FOR SURGICAL MANAGEMENT OF SUBLUXATED LENSES

Ehud I. Assia, MD and Michael E. Snyder, MD

Subluxation of the lens, either the natural crystalline lens or an artificial intraocular lens (IOL), resulting from dehiscence or weakness of the lens zonules is one of the most complex surgical challenges in modern cataract surgery.

Severe phacodonesis and pseudophacodonesis is usually treated by removal of the entire lens and replacing it with an anterior chamber IOL (ACIOL) or scleral-/iris-fixated posterior chamber IOL (PCIOL). If a sufficient number of zonules are still intact, preservation of the lens capsule using capsular stabilizing devices provides some significant advantages over IOL exchange. An intact capsular plane does the following:

• Maintains the barrier between the anterior and posterior segments of the eye
  
• Maintains the integrity of the vitreous body
  
• Separates and prevents the IOL material from chafing the uveal tissue that may result in uveitis-glaucoma-hyphema syndrome
  
• Uses the remaining intact zonular fibers to support the implanted lens

Further, an intact capsular bag-IOL complex precludes iris capture around the margin of either an ACIOL or a sutured PCIOL, even if perfectly positioned.

Some capsular stabilizing devices support the capsule at the equator; others support the capsular bag at the anterior capsulorrhexis edge. Still others yet provide support at both locations. Some of these support devices are intended for temporary, intraoperative use only, while others are designed for either short- or long-term support. This chapter will focus on devices that can be used for both indications.

Equatorial supporting devices include the Cionni ring and its modifications, such as the Ahmed segment and the Malyugin/Cionni ring (all by Morcher GmbH). The circumferential rings occupy most, or a portion, of the equatorial lens capsule. A fixation element at the shaft or the terminal end of the ring bypasses the anterior capsulorrhexis and is suture fixated to the sclera.^1–4 Insertion of a ring into a flaccid and unstable capsule in the presence of significant zonular dehiscence may potentially worsen zonular rupture during ring positioning and rotation.

Both capsular fixation rings and capsular segments have their point of fixation centripetal to the capsular equator, inducing a torque on the fixation element. With the Cionni and Malyugin/Cionni rings, the torque at the fixation element site is counteracted by the opposing zonules on the opposite side of the capsule complex. For the Ahmed segment, this torque is opposed only by the tensile strength of the anterior capsule. In cases with a weak anterior capsule or an eccentric or large capsulorrhexis, tension on the Ahmed segment can cause the device to slip out of the capsular bag entirely.

The capsular anchor (AssiAnchor; Hanita Lenses) was designed to provide localized support to a section of the anterior lens capsule at the area of zonular dehiscence as well as the corresponding capsular equator. The capsular anchor is a uniplanar polymethylmethacrylate device resembling a marine anchor in its shape. The central rod is placed in front of the anterior capsule, and the 2 lateral prongs are positioned behind the anterior capsulorrhexis edge, resulting in a firm grasp of the anterior capsular rim. The tips of the prongs extend peripherally to the capsular equator to provide localized equatorial support5–7 (Figure 10-1). Furthermore, the fixation element rests peripheral to the capsular equator and does not induce meaningful torque when the fixation suture is tightened.

Management of Subluxated Crystalline Lens

An intact anterior continuous curvilinear capsulorrhexis (ACCC) is a prerequisite for anchor fixation. The anterior lens capsule is separated from the lens material using an ophthalmic viscosurgical device (OVD) to create a 2.5-mm (approximately 2 clock hours, 60-degree) pocket for a 5-mm capsulorrhexis. Either a 9-0 polypropylene (Prolene; Ethicon) or CV-8 expanded polytetrafluoroethylene (Gore-Tex; WL Gore & Associates; this is an off-label use of this suture material) is placed 1 to 2 mm from the limbus at the desired fixation point, using either a combined ab interno/ab externo approach or a forceps suture retrieval approach. For the combined ab externo/ab interno approach, the suture is placed ab externo through the desired fixation point posterior to the limbus, externalized from the anterior chamber via the main incision (2.5 mm), then reinserted into the anterior chamber and passed ab interno through the scleral wall approximately 2 mm parallel to the original insertion point. The suture can be threaded through the hole at the base of the anchor device prior to placing the suture through the second external pass. Alternatively, the suture loop that remains hanging outside the wound after both passes are complete can be wrapped around the neck of the central rod of the anchor (Figure 10-2). In an alternative iteration with forceps retrieval, 2 scleral openings are created ab externo at the desired level of fixation, and a length of suture is then placed into the anterior chamber through the corneal incision. Microforceps are externally introduced through the sclerotomy, and the suture is grasped and externalized. The other end is similarly retrieved from the paired sclerotomy. Again, the suture may be passed through the fixation eyelet on the anchor before the second suture end is retrieved, or the loop can be draped around the core of the anchor. The capsular anchor is then inserted into the anterior chamber and pulled toward the ACCC. One lateral arm is positioned underneath the capsulorrhexis edge followed by slight rotation and positioning of the second arm beneath the anterior capsule. Stabilizing the capsule margin with microforceps or elevating the capsule margin with a Sinskey hook during the placement of the second arm can facilitate this slightly awkward maneuver. The 2 prongs are thus positioned underneath the lens capsule, while the central rod is in front to create a firm clipping of a wide section of the anterior capsule to the scleral wall. The rounded tips are positioned at the capsular equator to provide additional segmental equatorial support. The anchor can now be tightened and secured with a temporary, releasable suture to enable centration of the subluxated lens prior to phacoemulsification using routine surgical techniques. A PCIOL is then implanted within the capsular bag, and the tension in the anchor’s tethering suture to the scleral wall can be adjusted to optimize centration of the IOL (Figure 10-3). It is critical that this step be performed within a well-pressurized globe so that the final IOL position does not shift when the globe is reinflated. The suture knot can then be secured with locking throws. Because the suture is not tied to the device, it can be rotated and buried within the sclera, obviating any need for scleral flaps. Alternatively, phacoemulsification or lens aspiration can be performed first before inserting the capsular anchor into the evacuated lens capsule and securing it to the sclera.

A suture threaded through the positioning hole can also serve as a safety suture during implantation, when the device might inadvertently dislocate posteriorly through the large zonular defect, especially following anterior vitrectomy and removal of the vitreous cushion. If the surgeon opts to wrap the suture around the neck of the central rod, one option is to thread a separate temporary safety suture through the hole that can be pulled out once the anchor is in its final position.

In cases of a large zonular dialysis (6 to 9 clock hours), multiple anchors can be used, distributed evenly across the area of the missing zonules. Also, in many eyes with zonulopathy, such as with pseudoexfoliation, retinitis pigmentosa, and Marfan and Weill-Marchesani syndromes, the zonules that are seemingly normal at surgery may progressively weaken and break in subsequent years. Depending on the meridian of the original dehiscence, it might be advantageous to prophylactically implant 2 devices, especially if the original fixation point is inferior (Figure 10-4), even though most of the remaining zonules seem intact.

A capsular tension ring (CTR) can be implanted in addition to the capsular anchor in cases with a large zonular defect. The purpose of the CTR is to maintain the round contour of the lens equator, to prevent capsular shrinkage, and to equally distribute the forces acting on the capsule circumferentially. Insertion of the CTR after the capsule is secured to the scleral wall by the anchor is usually easier and safer than prior to fixation of a loose and lax capsular bag.

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