Preventing posterior capsule opacification in paediatric cataract surgery
Cataract surgery in children is challenging because of the likelihood of posterior capsule opacification. This can be overcome with primary posterior laser capsulotomy coupled with bag-in-the-lens technology.
Paediatric cataract is a major cause of visual impairment in young patients worldwide and operating on congenital, early childhood or juvenile cataract is certainly challenging. In the hands of an experienced surgeon and a specialised team, the hurdles posed by the specific conditions of a young, developing eye can be overcome. The bane of the management of paediatric cataract, however, is posterior capsule opacification (PCO), which develops rapidly in the weeks and months after lens removal.
Close to or as much as 100% of young children will develop PCO as the most frequent complication in paediatric cataract surgery. Leaving the posterior capsule intact has been recognised for quite some time as a prerequisite in the pathogenesis of PCO and interventions on the posterior capsule have been introduced as a means to prevent or at least reduce the probability of PCO formation.1
The introduction of the femtosecond laser into cataract surgery has been—at least in our view, as pioneers of laser cataract surgery (LCS) in central Europe and with experience of close to 10,000 interventions now—a game changer in many respects, and I had the privilege to describe to readers of Ophthalmology Times Europe® in the November 2021 issue the potential of its employment in paediatric cataract surgery.2 Readers should be reminded that laser cataract surgery in children is, like so many interventions on our youngest patients, an off-label procedure.
Posterior capsulotomy has been described as an option for reducing PCO formation in paediatric cataract patients. In our experience, primary posterior laser capsulotomy (PPLC) is a completely new approach, not least because an anterior vitrectomy is usually not necessary.
This in turn reduces the risk of one of the most vicious complications of early childhood cataract surgery, aphakic glaucoma, significantly—in fact, to zero. Aphakic glaucoma is one of the most damaging and most difficult-to-manage forms of glaucoma.
In PPLC, the anterior hyaloid membrane of the vitreous stays intact and thus the influence of vitreous substances (which are discussed among the probable causes of aphakic glaucoma) is reduced to nil.
Procedure in young eyes
Figure 1. Overview of the OR setting with the femtosecond laser (Catalys, Johnson & Johnson) within the OR aside the surgical microscope.
When undertaking LCS in paediatric patients, we perform capsulotomy with the laser (Figure 1); unlike in adult LCS, the lens is not fragmented because it can usually be removed by aspiration only.
Under general anaesthesia, the child is placed under the laser, then the smaller fluid-filled interface will be slowly and cautiously lowered towards the eye. After gently connecting with the ocular surface, the laser will perform anterior capsulotomy; when entering the clinical data in the platform’s software, we use the Bochum correction formula (described previously2). Anterior capsulotomy is performed and small tags—which appear rarely—are gently removed manually.
The posterior capsule is meticulously polished; in paediatric cataracts, pupil dilation tends to be suboptimal. Ophthalmic viscosurgical device (OVD) is introduced sparingly to avoid pushing the posterior capsular too far back. The posterior capsule is elevated by OVD injection through a small opening in order to change its shape from concave to more convex.
After lens removal under the operating microscope, the young patient is once again positioned under the laser. Primary posterior laser capsulotomy is performed after perfectly aligning the anterior and the posterior capsules. The laser shots are fired from posterior towards anterior.3
The BIL implant or BIL lens is a foldable hydrophilic lens, which consists of a biconvex optic and two elliptical plane haptics and is prepared in a cartridge for implantation. In adults, it requires a main incision of about 2.8 mm, but a special BIL lens for paediatric eyes is commercially available, which is smaller than the one implanted in adult eyes and can be exchanged when the child is older.
As first described by Marie-José Tassignon in 2002,4 during bag-in-the-lens (BIL) technique with two well-centred capsulotomies of almost identical size, anterior and posterior capsules are placed in this special IOL’s flange for insertion. We implant the lens by aligning the lower haptic to the 6 o’clock/12 o’clock meridian. A small spatula is used to protect the IOL from coming too deep into the anterior chamber during implantation.
Figure 2. Paediatric BIL with the anterior and posterior capsule within the “groove” of the optic (view through the microscope). (Images courtesy of Prof. Burkhard Dick)
When the BIL lens is completely inserted and unfolded, the posterior haptics are placed behind the posterior capsule and the anterior haptics in front of the anterior capsule, which keeps both capsules in the “groove” that is so characteristic of this innovative type of IOL. This procedure allows perfectly centrated and stable positioning of the lens (Figure 2).
Intraoperative use of acetylcholine ensures that the iris covers the haptics. In older children, we make sure the incisions are not leaking; in younger children we use a suture for watertight wound closure.
Minimal remnants of OVD will be resorbed over time.5 Postoperative care is as usual for paediatric cataract patients except for the additional postoperative application of pilocarpine 1% three times daily for 2 days starting directly at the end of the procedure.
PPLC is a generally safe and effective procedure; we have documented its excellent safety profiles after 6 months6 and our 2-year results are currently under review. The same can be said about the BIL technology. A recent publication demonstrated that this implant does not induce an elevated risk for postoperative cystoid macular oedema.7
The superiority of secondary bag-in-the-lens implantation over ciliary sulcus implantation of an IOL in aphakic children, in terms of fewer adverse effects, best-corrected visual acuity and IOL centration, was recently described by Liu et al.8 Our opinion that cataract surgery has a great tool promising much lower PCO rates in children than could have been hoped for just a year ago is supported by a 2022 publication from Norway: in 50 eyes of 30 patients younger than 12 years at the time of operation, who had received a BIL since 2013, 92% had a visual axis free of PCO.9
In our experience PCO occurs only if the capsule edges are not positioned in the optic groove between both haptics. This is promising data indeed. And yet, cataract surgery in children is always just the first step on the long and winding road to optical rehabilitation.
