Subluxation of the crystalline lens is typically associated with significant impairment of vision and usually requires surgical intervention. Because the subluxated lens is positioned off-axis, removal of the lens material and implantation of an artificial lens within the malpositioned capsule will necessarily result in a decentered IOL.
The practical options to manage subluxated lenses include (1) removal of the entire crystalline lens, including its capsule, and implantation of either an anterior chamber IOL or fixation of a posterior chamber IOL to the iris or the sclera using sutures or biologic glue and (2) preservation and suture fixation of the lens capsule to the scleral wall using a capsule-stabilizing device. There are two kinds of stabilizing devices: equator- and capsule-supporting devices.
EQUATOR-SUPPORTING DEVICES
Mild zonular dehiscence (less than 3 clock hours) may result in no or minimal lens decentration. In these cases, implantation of a capsular tension ring (CTR) may maintain the round contour of the capsular equator and provide sufficient support for a posterior chamber IOL. In eyes with zonular dehiscence larger than 3 clock hours, additional suture fixation to the scleral wall is usually needed.
Suturing a conventional CTR by passing the needle through the capsule may result in a radial tear extending to the posterior capsule, jeopardizing posterior chamber IOL fixation. Robert J. Cionni, MD, developed a modified CTR with one or two short loops extending perpendicular to the plane of the CTR and bypassing the anterior capsule through the anterior capsulorrhexis. The terminal fixation eyelets can be sutured to the scleral wall using a nonabsorbable suture material such as polypropylene or polytetrafluoroethylene (Gore-Tex). The integrity of the capsule is thus maintained to provide long-term stable and central fixation of the IOL.
The Cionni ring gained worldwide popularity and is now the leading device in use. Nevertheless, there are still two main drawbacks to the Cionni modified CTR: (1) rotation of the ring inside a bag that is unstable through the entire circumference of the capsular equator may cause significant damage to the remaining zonular fibers and increase the dehiscence and (2) the Cionni ring cannot be injected into the bag like a conventional CTR because the fixation loop is perpendicular to the ring and located away from the end of the CTR.
Iqbal Ike K. Ahmed, MD, addressed the first problem by shortening the ring to create a capsular tension segment (CTS) that occupies only part of the capsular equator. To overcome the second problem, Boris Malyugin, MD, recently modified the Cionni ring by locating the fixation element at the terminal part of the ring, enabling it to be inserted into the capsular bag using a designated injector.
CAPSULE-SUPPORTING DEVICE
In 2004, we developed a capsular anchoring device (AssiAnchor; Hanita Lenses; Figures 1–5), which is based on a concept different from that of equatorial rings. The AssiAnchor is a 2.5-mm wide PMMA uniplanar implant and, therefore, can be inserted through a regular corneal incision. The two lateral arms of the device are inserted through the capsulorrhexis and positioned behind the anterior lens capsule, while the central element is placed in front of the anterior capsule. Thus, it creates a clip that adheres to a small segment of the anterior capsule. The tips of the lateral arms are designed to reach the lens equator and provide segmental equatorial support. The anterior rod is sutured to the scleral wall using a nonabsorbable suture.
A conventional CTR can be used in conjunction with the AssiAnchor to maintain the round contour of the capsular equator. The AssiAnchor is preferably inserted prior to lens removal in order to reposition and stabilize the lens and, thus, facilitate removal of lens material from the unstable subluxated capsule. Once the lens is secured to the sclera, routine phacoemulsification and implantation of a posterior chamber IOL are performed. The suture knot is then buried in the scleral tissue under the conjunctiva, and no flaps are required.
We have used these devices in a variety of cases, including penetrating and blunt traumatic zonular rupture, lens subluxation secondary to pseudoexfoliation, high myopia, and hereditary zonular pathologies such as Marfan syndrome, primary ectopia lentis, and microspherophakia. Patient age ranged from late teens to mid 70s, and all of the traumatic cases were men. AssiAnchors were used in both eyes in patients with bilateral disease, usually hereditary zonular defects. In four eyes in which the zonular dialysis was 6 hours or greater, two AssiAnchors were implanted in the same eye. CTRs were used in six eyes to help maintain a round capsular bag and distribute even support to the large area with missing or weakened zonules.
The AssiAnchor is inserted easily in eyes with relatively soft lens material (eg, congenital and traumatic cases), whereas hydrodissection and viscoseparation of the lens material from the capsule are needed in eyes with advanced cataract. The uniplanar design of the device allows smooth insertion through a tight corneal incision; however, placement of the two lateral arms behind the capsule and the central element in front requires some intraocular manipulation. A new model of the AssiAnchor with the lateral arms located in a lower plane than the central rod is now being designed and tested.
The AssiAnchor occupies only a small portion of the capsule, about 1 clock hour, and it does not necessarily require a completely intact capsulorrhexis. This was evident in a case of traumatic cataract associated with rupture of the anterior lens capsule. Surgery was performed a few months after trauma, and an AssiAnchor was used despite two radial tears, which did not extend posteriorly during surgery.
The device was also used in three eyes in which posterior chamber IOLs, implanted in the bag several years earlier, had subluxated. A small pocket was made using a spatula, and an ophthalmic viscosurgical device (OVD) was used to separate the capsule from the IOL and facilitate positioning of the device. The displaced IOLs were recentered and secured to the scleral wall through a relatively closed system. Thus, the AssiAnchor can be used not only to manage subluxated crystalline lenses but also to treat malpositioned posterior chamber IOLs.
The AssiAnchor has been in clinical use since 2007, and, to the best of our knowledge, all of the implanted lenses are still stable and central. No device-related complications were recorded, and no eye with an AssiAnchor was reoperated.
CONCLUSION
Lens subluxation is a major challenge to eye surgeons. A variety of surgical techniques and devices are available to achieve successful clinical results and restore useful vision.
Ehud I. Assia, MD, is a Professor of Ophthalmology at Tel-Aviv University, Director of the Department of Ophthalmology at Meir Medical Center, and Medical Director of Ein-Tal Eye Center in Israel. Dr. Assia states that he is a consultant to Hanita Lenses and Biotechnology General (Israel) Ltd., receives research fees from Vision Care Technologies, is a shareholder in IOPtima, and is the Founder and Chief Medical Officer of APX Ophthalmology and VisiDome. He may be reached at tel: +972 9 7472151 or +972 3 5433222; e-mail: ehud.assia@clalit.org.il or assia@netvision.net.il.
Suggested reading
- Hasanee K, Butler M, Ahmed II. Capsular tension rings and related devices: current concepts. Curr Opin Ophthalmol. 2006;17:31-41.
- Ton Y, Michaeli A, Assia EI. Repositioning and scleral fixation of the subluxated lens capsule using an intraocular anchoring device in experimental models. J Cataract Refract Surg. 2007;33:692-696.
- Assia EI, Ton Y, Michaeli A. Capsule anchor to manage subluxated lenses: initial clinical experience. J Cataract Refract Surg. 2009;35(8):1372-1379.
- Hoffman RS, Snyder ME, Devgan U, Allen QB, Yeoh R, Braga-Mele R. Management of the subluxated crystalline lens. J Cataract Refract Surg. 2013;39(12):1904-1915.
