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Is there a role for MIGS devices in the treatment of pediatric glaucoma?
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Potentially yes, but more studies are needed
For children with primary congenital glaucoma, the pathology is at the trabecular meshwork, and for this reason, Schlemm’s canal-based surgery remains the treatment of choice. Goniotomy and trabeculotomy have reasonable success rates and a low risk for complications. If angle surgery fails, glaucoma drainage device surgery and trabeculectomy with mitomycin C can be considered, but these procedures carry significant risks and are difficult to perform in the pediatric population.
New devices such as the InnFocus microshunt (Santen Pharmaceutical) and the Xen gel stent (Allergan) may have a role in glaucoma surgery in the pediatric population, but additional data regarding their safety and efficacy in adults are needed before I would consider implanting them in a young child. Although these two implants are made from material that is proven to induce less tissue inflammation, we remain uncertain as to how they would respond when faced with a child’s robust healing response. The Xen gel stent is 6 mm in length with a luminal diameter of either 45 µm, 63 µm or 140 µm. Implants with a smaller luminal diameter may not achieve the low IOPs that children with advanced disease require, while the larger diameter implants may be associated with a significantly greater risk for hypotony. Hypotony is a challenge to manage in adult patients and even more difficult in the pediatric population. The InnFocus microshunt is 8.5 mm in length and has a 70 µm luminal diameter; like the Xen gel stent, there is no reservoir attached to this device.
These devices offer several advantages over glaucoma drainage device surgery and trabeculectomy, including a decreased potential risk for hypotony due to the small luminal diameter of the implant, a shorter implantation time and little postoperative management. As mentioned earlier, these devices may be safer alternatives, but they may not achieve the desired IOP reduction that is required. It is all about achieving the right risk-reward profile. Although glaucoma surgeries have evolved over the last few decades, many are still challenging to perform in the pediatric population and associated with great risk. We continue to look for better options, and some of the microinvasive procedures that have come along may be suitable for use in the pediatric population both now and in the years to come.
Joseph F. Panarelli, MD, is assistant professor at New York Eye and Ear Infirmary of Mount Sinai, New York. Disclosure: Panarelli reports he is a consultant to Allergan and Aerie Pharmaceuticals and receives honoraria from Glaukos.
Not yet, in a population that requires aggressive IOP control
The surgical approach of pediatric glaucoma is dichotomous. If angle surgery can be performed, it usually is. If angle surgery cannot be performed or has failed, aggressive shunts (or less frequently, filters) are often needed for pressure control. In contrast to adults, many pediatric glaucoma patients do not have the luxury of time for medication micromanagement or modestly efficacious surgeries due to the difficulty in gauging treatment outcome, which often involves examinations under anesthesia, and the high risk for amblyopia. Thus, early, definitive IOP control is an imperative in the management of pediatric glaucoma.
To examine the titular question more closely, we can ask the following — are there MIGS devices that significantly improve angle surgery and/or allow definitive IOP control early on? The various MIGS trabecular ablative devices, such as the Trabectome (NeoMedix), the Kahook Dual Blade (New World Medical), and Trab360 and Visco360 (both Sight Sciences) are variations of the goniotomy knife, a main staple of childhood glaucoma surgery since the 1940s, which could be considered as the original MIGS given its simplicity, safety and efficacy. Each of the new devices offers small theoretical advantages over the traditional device, although at significantly increased costs. None has been shown to be more efficacious than the standard goniotomy in the pediatric population. The Trab360 and Visco360 devices may offer higher success rate compared with a single goniotomy by allowing near-circumferential incision of the trabecular meshwork , although goniotomy augmented with circumferential ab interno trabeculotomy using blunted 5-0 Prolene can achieve the same anatomical outcome at a fraction of the cost. None of the subconjunctival or suprachoroidal devices on the market are likely to outperform the standard filter or tube shunt.
In summary, pediatric glaucoma surgery should be definitive, safe and inexpensive. Currently, no trabecular ablative MIGS device outperforms goniotomy or ab interno trabeculotomy, and no subconjunctival or suprachoroidal device has demonstrated advantages over traditional tube shunts and filters in this population that requires aggressive pressure lowering. Thus, MIGS does not yet have a role in the routine treatment of pediatric glaucoma.
Ta Chen Peter Chang, MD, is assistant professor of clinical ophthalmology and pediatrics at Bascom Palmer Eye Institute, Miami. Disclosure: Chang reports he receives royalty payments for his book Clinical Decisions in Glaucoma, 2nd Edition.