BEAN-SHAPED RING SEGMENTS AND BAG–IN–THE-LENS IOL IMPLANTATION

Marie-José Tassignon, MD, PhD, FEBO, FEBOS-CR and Sorcha Ní Dhubhghaill, MD, PhD, FEBO, FEBOS-CR

The best place to implant an intraocular lens (IOL) is within a clean, intact capsular bag with strong zonular support. The capsular bag maintains IOL stability and proper postoperative positioning. Perfect lens placement is not always possible, however, and in cases where the capsule or zonules are compromised, standard intracapsular IOL implantation may prove very difficult. Causes of capsular instability are numerous and include pseudoexfoliation, Marfan and Weill-Marchesani syndromes, homocystinuria, and finally, aging.¹ The capsule can also be damaged by accidental or iatrogenic trauma.² Clinical signs of capsular instability may be seen preoperatively and include iridodonesis, phacodonesis, and partial or total crystalline lens dislocation. Posterior lens subluxation may not be obvious at the slit lamp and may only become apparent when the patient is supine. Surgeons should also remain alert for intraoperative clues of zonular weakness. These may include increased mobility of the capsular bag during capsulorrhexis, difficulties in hydrodissection and nuclear rotation, peripheral vitreous prolapse, and excessive deepening of the anterior chamber while introducing the phaco probe.

The IOL implantation options with zonular weakness depend on severity.^3–7 While mild zonulopathy may be amenable to a large 3-piece IOL or a capsular tension ring (CTR), larger areas of zonular weakness may require a modified CTR that can be sutured to the sclera. With the most severe zonulopathy, the capsule itself may be unusable and alternative lens placement methods such as sulcus fixation, scleral fixation (sutures or glue), iris fixation, or anterior chamber lens implantation may be required. One of the main drawbacks of suturing an IOL is the risk of late dislocation. Suture fixation is most often performed using a 9-0 or 10-0 Prolene (Ethicon) suture but these may degrade over the long term. Gore-Tex (WL Gore & Associates) has been proposed as a longer-lasting alternative, but specific Gore-Tex sutures for ophthalmic use have not been developed. The currently available Gore-Tex sutures are bulky and can be difficult to tie properly.

In our clinical practice we routinely use the bag-in-the-lens cataract technique. The bag-in-the-lens technique is a unique approach to lens implantation and, to date, has been validated clinically in more than 20,000 eyes. It is gaining popularity in Europe, where it is manufactured by Morcher GmbH. In this technique, the lens is implanted within matching anterior and posterior capsulorrhexes.⁸ This method of IOL fixation captures the capsule in the groove of the lens, thereby preventing complications such as posterior capsule opacification and capsulophimosis. This fixation method also has the advantage of maintaining a high degree of centration, resistance to rotation and makes any IOL exchange easier.^9–12 The position of the bag-in-the-lens IOL, however, like other IOLs, relies heavily on capsular and zonular integrity. In cases where the zonules were weak or lacking, the bag-in-the-lens IOL was difficult to use and the aforementioned advantages of bag-in-the-lens fixation IOL were not attainable.

The bean-shaped ring segments (“beans”) were developed as a tool to reinforce capsular support and to allow bag-in-the-lens implantation in cases where the capsule or zonules were unstable (Video 11-1). We initially reported the bean insertion technique within the capsular bag in a case of traumatic cataract.¹³ After examining the outcome in trauma cases, we extended the indication for bean segment implantation to include cases with torn capsules and loose zonules, whether congenital or acquired.¹⁴ Prior to the development of the bean support, we fixated a loose bag-in-the-lens IOL by looping a thread of 10-0 Prolene into the groove of the implant and fixating it at the sclera (Figure 11-1). Although this did improve the lens centration, the bean implants are a far more reliable method of achieving the same goal. Based on our initial experience and clinical observations, the second generation of bean-shaped rings was adapted to include a hole in the outer ring. This hole allows a suture to be attached for scleral fixation in extreme cases where there is very little zonular and capsular support (Figure 11-2).

In this chapter, we will focus on the technique of bean implantation in patients with loose zonules from any cause. The first generation of bean-shaped ring implants was developed in 2012 in collaboration with Olaf Morcher, the CEO of Morcher in Germany. Morcher continued the pioneering work of his father, who started his IOL manufacturing company in collaboration with the Dutch ophthalmologist Cornelius Binkhorst after World War II. This was during the same period that Rayner started his company in the United Kingdom in collaboration with Harold Ridley. Olaf Morcher has a strong interest in optics, biomaterials, and IOL optic design and remains committed to novel ideas, treatment strategies, and applications.

The first outcomes of the bean devices supporting the bag-in the-lens implant in cases of capsular or zonular instability were published in 2017.¹⁴ We described how the bean-shaped ring segments, or beans, were designed to fit into the groove of the bag-in-the-lens IOL at the equator of the lens and to be positioned in the ciliary sulcus at the outer side. The indications were primary or secondary loose zonules with crystalline lens dislocation, traumatic cataract, and IOL exchange converting a lens-in-the-bag to a bag-in-the-lens or after uneventful bag-in-the-lens implantation revealing unstable capsule support and compromising the long-term stability of the bag-in-the-lens. The best corrected and uncorrected visual acuity of the first 50 cases were highly satisfactory, showing a mean visual acuity improvement of 0.35 (range between different groups: 0.28 to 0.43 decimal Snellen) in the study cohort. The best refractive outcomes were achieved in the traumatic group and the IOL exchange group.

We were initially extremely cautious in implanting patients, but with accumulating experience we have expanded our use of the bean technique. We consider using bean support whenever zonular weakness is suspected, including in children with congenital cataract associated with loose zonules. We also use the beans many months or years after the primary surgery has been performed, depending on when the loose zonulae become manifest.

Stay updated, free articles. Join our Telegram channel

Join