Minimally invasive glaucoma surgeries (MIGS) are quickly earning a place in the glaucoma treatment regimen. Their demonstrated efficacy, along with improved safety and faster recovery compared with traditional surgeries such as trabeculectomy, have made MIGS a good option for patients showing glaucomatous damage, progression or even those who want to reduce their dependence on topical therapy.1 Many MIGS target the traditional outflow pathway, either by bypassing or removing the trabecular meshwork or by reconstructing Schlemm’s canal. But two recently approved devices have different approaches.
Follow a New Path
The CyPass Micro-Stent (Alcon), a fenestrated stent that connects the anterior chamber to the supraciliary space, is used with cataract surgery to reduce intraocular pressure (IOP) in patients with mild to moderate primary open-angle glaucoma. Using the corneal incisions already created for cataract extraction, the surgeon places the stent posterior to the scleral spur. The curved design allows natural passage into the supraciliary space, while retention rings are designed to keep the stent in place. In the COMPASS trial, which compared cataract extraction plus CyPass insertion with cataract extraction alone, the group receiving CyPass showed a 7.4mm Hg reduction in mean IOP, compared with 5.4mm Hg with only cataract extraction at two years.2
Unlike the CyPass, the Xen 45 gel stent (Allergan) mimics the outflow pattern of traditional glaucoma procedures by draining aqueous into the subconjunctival space, but with the less invasive ab interno approach. This stent is indicated as a stand-alone procedure or with cataract surgery for patients with open-angle, pseudoexfoliative or pigmentary glaucoma who failed maximum topical therapy or other filtering procedures. The Xen, preloaded in a single-use injector, is inserted through the trabecular meshwork, creating a scleral channel through which the stent connects the anterior chamber to the subconjunctival space. A clinical trial of 65 patients demonstrated a drop in IOP from a mean of 25.1mm Hg preoperatively to 15.1mm Hg postoperatively, with a reduction in medications from 3.5 before the procedure to 1.7 after.3
As with standard cataract surgery, patients will be prescribed a combination of antibiotics, steroids and nonsteroidal anti-inflammatory drugs after the procedure. Glaucoma drops may be adjusted or discontinued depending on the resulting postoperative IOP.
Gonioscopy is critical in the management of any MIGS procedure and is especially useful during pressure spikes to monitor for proper stent placement, potential iris obstruction or hemorrhage through the stent. Patients should also be watched closely in the postoperative period for hypotony, hyphema, iritis and corneal edema. Patients with the Xen stent should also be observed for any flattening of the subconjunctival bleb, as needling of the bleb was required in 32.3% of patients.3
MIGS are an exciting addition to the glaucoma management regimen. These two new procedures in particular provide many patients yet another avenue for preventing glaucomatous damage.
Dr. Kruthoff practices at Virginia Eye Consultants in Norfolk, Va., with a focus on perioperative glaucoma care.
1. Saheb H, Ahmed II. Micro-invasive glaucoma surgery: current perspectives and future directions. Curr Opin Ophthalmol. 2012;23(2):96-104.