Rethinking intraocular lens implantation with the ‘bag-in-the-lens’ implant

Since the groundbreaking work of Sir Harold Ridley, the standard of care in cataract surgery is to place an intraocular lens implant (IOL)  ‘in the bag’. That is to say, when the cataractous crystalline lens is removed, the suspensory lens capsule is preserved to support the new lens. Placing the lens in the bag closely emulates the natural lens position and has come to be known as ‘lens-in-the-bag’ surgery. The lens in the bag approach is well standardised and widely regarded as the best and safest surgical method to achieve high quality postoperative results. The approach is not without its downsides however. Placing an IOL in the capsular bag can elicit a cellular response and despite the high biocompatibility of modern IOLs, a form of ‘foreign body’ reaction can and does occur.

During surgery, after the cataract is removed from the capsular bag, the residual cortex and epithelial cells are also aspirated to create a clear, transparent bag for IOL implantation. In most cases this provides a quality visual result but in some patients residual lens epithelial cells proliferate in the capsule. As they grow they can cause a haze in the posterior capsule known as posterior capsular opacification (PCO, Figure 1). PCO is also referred to as ‘secondary cataract’ as the patient may feel that the cataract is returning and can occur in up to 80% of patients 10 years post-cataract surgery.¹ But proliferation of cells in the bag can also have a more profound effect on the IOL. In cases of capsule fibrosis and contraction, the IOL may be shifted out of it optimal position and the results of a successful surgery can be lost.

In adults, PCO may be treated with a simple Nd-YAG laser capsulotomy, a short and painless procedure that confers very few risks (Figure 2). In younger people and in children however, the cellular response in the capsule is beyond that which can be handled by laser and ocular surgery is required. Cases of significant capsular contraction and fibrosis can rarely be treated by laser and require an intraocular lens manipulation or IOL exchange which is considerably riskier than standard cataract surgery.

Over the past 10 years in Antwerp University Hospital, we have been using a unique design of IOL, which helps address these postoperative issues. Instead of placing the lens into the bag, we make circular openings (anterior and posterior capsulorhexis) in the bag itself and insert a lens into this space. This ‘bag-in-the-lens’ construction is commercially available (89A, Morcher GmBH, Germany), and is a monofocal spherical hydrophilic lens with two elliptical flange haptics (Figure 3). When the lens is in position, the capsular bag slips into a groove in the lens.² In this way, the bag suspends the lens in the eye (Figure 4). The technique has a number of advantages. Firstly, the centre of the capsule is removed, so the visual axis remains clear and the risk of PCO is eliminated.³ Secondly, as the capsule fibroses over time, rather than disturbing the lens position, it appears to reinforce the lens stability.^4,5 Since paediatric cataract cases have the highest risk of complex posterior capsular opacification, we began using the BIL implant in this population,⁶ but over time we have expanded the indications for the lens and it is now our first line lens for most cataract surgeries. It is also the technique that is taught to our resident trainees. In cases of weak zonular fibres as in myopia we recommend the use of a capsular tension ring to further support the lens suspension.

This is admittedly a more complex way to insert an IOL and it requires more time and surgical steps to implant. Naturally there is also a learning curve but once the technique is mastered, it has a number of advantages over the standard surgery. Many surgeons have expressed concerns over opening the posterior capsule. In standard cataract surgery if this capsule is accidentally ruptured, there is an increased risk of postoperative complications; if the BIL technique is performed by the controlled procedure that we describe,⁷ there is no increased risk associated with the surgery. The key is to preserve the integrity of the anterior hyaloid face, which allows the eye to retain the properties of an eye with an intact PC, unlike an accidental capsule rupture.⁸ We do this by making a very small controlled puncture in the posterior capsule followed by injecting ophthalmic viscosurgical device into the space of Berger, pushing back the anterior hyaloid space a safe distance away.
We have reported the surgical outcomes of 807 BIL patient outcomes and have documented a rate of retinal detachment of 1.24%. Cystoid macular oedema was documented in one patient and one case of toxic anterior segment syndrome was reported. A more minor complication that occurs occasionally is postoperative capture of the iris in the IOL groove. In most cases the iris may be freed with pupil dilation. Rarely, the iris must be disengaged surgically. In spite of this, we find the BIL implant to be a significant improvement of standard in the bag surgery in terms of centration and prevention of PCO complications, reducing the need for additional laser capsular treatment. As multifocal lens technologies and femtosecond laser surgeries continue to improve, we plan to integrate these state of the art developments into the BIL approach to provide the best possible long term results for all patients.

Figure 1: Examples of posterior capsular opacification

Figure 2: After opening of the posterior capsule by Nd-YAG capsulotomy

Figure 3. The BIL implant front and profile

Figure 4: Four examples of BIL implantation

References

1. Apple D et al. Posterior capsule opacification. Surv Ophthalmol 1992;37:73–116.
2. Tassignon MJ et al. Clinical outcomes of cataract surgery after bag-in-the-lens intraocular lens implantation following ISO standard 11979–7:2006. J Cataract Refract Surg 2011;37:2120–9.
3. Leysen I et al. Cumulative neodymium:YAG laser rates after bag-in-the-lens and lens-in-the-bag intraocular lens implantation: comparative study. J Cataract Refract Surg 2006;32:2085–90.
4. Verbruggen K et al. Intraocular lens centration and visual outcomes after bag-in-the-lens implantation. J Cataract Refract Surg 2007;33:1267–72.
5. Rozema JJ et al. Changes in rotation after implantation of a bag-in-the-lens intraocular lens. J Cataract Refract Surg 2009;35:1385–8.
6. Tassignon MJ et al. Bag-in-the-lens intraocular lens implantation in the pediatric eye. J Cataract Refract Surg 2007;33:611–7.
7. De Groot V et al. One-year follow-up of bag-in-the-lens intraocular lens implantation in 60 eyes. J Cataract Refract Surg 2006;32:1632–7.
8. De Groot V et al. Lack of fluorophotometric evidence of aqueous-vitreous barrier disruption after posterior capsulorhexis. J Cataract Refract Surg 2003;29:2330–8.