EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
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EW FEATURE 44 Combined procedures for glaucoma November 2014 AT A GLANCE • The iStent allows surgeons to better control a patient's glaucoma with fewer medications. • The best way to get started is to practice gonioscopy and angle manipulation in the OR during cataract surgery. • Surgeons should tailor the use of the device to those patients most likely to benefit. by Lauren Lipuma EyeWorld Staff Writer Implanting the iStent with cataract surgery offers IOP lowering with few risks W ith a low complica- tion rate and high safety profile, the iStent (Glaukos, Laguna Hills, Calif.) is an excellent option for lowering IOP in patients with mild to moderate glaucoma. The device is the only currently approved procedure for microinvasive glaucoma surgery, or MIGS. Malik Kahook, MD, profes- sor of ophthalmology, University of Colorado School of Medicine, Aurora, Colo.; Garry Condon, MD, chair, Department of Ophthalmol- ogy, Allegheny General Hospital, Pittsburgh; and Douglas Rhee, MD, chair, Department of Ophthalmol- ogy and Visual Sciences, University Hospitals Case Medical Center, Cleveland, shared their thoughts on the benefits and limitations of the device as well as pearls for getting started with the procedure. Benefits and limitations While the iStent cannot dramat- ically lower IOP like traditional glaucoma surgeries, the value of the device lies in its ability to reduce the number of medications a patient is taking, Dr. Condon said. Even with modest IOP reduction, the device allows the physician to better control a patient's glaucoma with fewer medications, he said. "If the implantation leads to 1–2 mmHg IOP lowering and a decrease in dependence on medications by microscope position, Dr. Rhee said, as well as familiarizing oneself with one-handed procedures, as one hand must hold the gonioprism. Proper inflation of the eye with viscoelastic also requires practice, Dr. Rhee said. Overinflating the eye can distort the anatomy and cause the canal to collapse, but underinflating can create striae and folds in the cor- nea when the gonioprism is pushed against it. "There's that balance you have to find where you've inflated the eye enough so that you can see—so the chamber is maintained, and it counterbalances the pressure that you're going to put on the eye with the lens," he said. Dr. Kahook stressed the need for concentration at the time of inser- tion. Complications associated with the device are usually the result of improper placement, he said. "Devices can fall out into the anterior chamber if not secured and can cause endothelial or iris trauma if placed inappropriately," he said. "This complication can be overcome by taking additional time to ensure proper placement and being compulsive about the positioning at the time of surgery." Getting started The surgeons agreed that the best way to get started with iStent im- plantation is to practice gonioscopy on cataract patients in the operating room at the time of surgery. "Tilting the patient's head and the scope can take some getting used to," Dr. Kahook said. "Doing this without the pressure of implantation will allow the surgeon to be more comfortable when the time comes to do the first implantations." Dr. Rhee also recommended tak- ing an instrument such as a cannula and manipulating it in the angle to get a feel for the magnification of the gonioprism. "Little movements that you're used to making are all of a sudden gigantic movements, so there's a small learning curve," he said. After getting comfortable with the view and angulation, Dr. Condon recommended participating in the wet labs offered by Glaukos to become familiar with device implantation. Combining phaco with MIGS device who can benefit from iStent implan- tation, and the surgeons agreed that finding a niche for the device is key to its success. "My advice would be to tailor the use of these devices to specific patients who might be more likely to benefit, such as those who are not tolerating or adhering to their medical therapy," Dr. Kahook said. Another group of ideal patients would be those whose pressures are under control but who require many medications, according to Dr. Rhee. Those patients are at high risk for an immediate postoperative IOP spike with cataract surgery alone. "You're just trying to get past that postoperative period where that spike might happen," he said. "I find that ab interno approaches are excellent for that." The learning curve The iStent gives cataract surgeons their first opportunity to include a glaucoma procedure along with cataract surgery—a major plus, Dr. Condon said. However, the physicians agreed that getting comfortable with iStent implanta- tion can be challenging for surgeons who are not completely familiar with operating in the anterior chamber angle. In addition to learning gonios- copy, iStent implantation and ab in- terno approaches in general require adjusting to differences in head and 1 drop, this is a great success in my opinion," Dr. Kahook said. "The main advantage of using MIGS devices is that they can provide modest IOP lowering, but at little cost to the patient from the stand- point of adverse events." Another benefit of the device is the fact that it does not prevent the patient from receiving additional glaucoma surgeries in the future if those are needed. "Sometimes you'll hit a home run and sometimes you won't," Dr. Condon said. "The important thing is that if you don't hit that home run, you haven't lost anything by trying." The ideal patient for a com- bined phaco and MIGS procedure is someone with uncomplicated, mild to moderate disease who requires a target IOP in the mid to upper teens, the physicians said. Good, iden- tifiable landmarks in the anterior chamber angle are also ideal, Drs. Condon and Rhee said. However, the Food and Drug Administration's restrictions on iStent use are problematic, Dr. Condon said, through no fault of the surgeon or the device. The fact that the iStent can only be placed in conjunction with cataract surgery limits the number of patients who can benefit from it, and the fact that only one device can be placed at a time limits its potential to lower IOP. Despite these limitations, there are significant groups of patients iStent about to be engaged into the trabecular meshwork Source: Doug Rhee, MD continued on page 46