Eyeworld

EW GLAUCOMA 60 January 2017 by Michelle Dalton EyeWorld Contributing Writer Dr. Moster recommends using a 25-gauge MVR blade to bisect the trabecular meshwork for about half of a clock hour and opening it up with additional viscoelastic to cut through the trabecular mesh- work, exposing the inner wall of Schlemm's canal, thereby creating a small micro goniotomy. That makes placement of an iStent much easier, she said, allowing surgeons to push the device forward "so it's well buried behind the trabecular meshwork." Because the "best place" to put an iStent is "where there's a lot of pigment and/or blood in Schlemm's canal," anticipate some bleeding from the site, Dr. Moster said. "Get used to the idea that there may be bleeding, the view may be obscured, you might have to use I/A to remove the blood and replace the ophthalmic viscosurgical device (OVD) and start again," she said. "This is not for the faint-hearted." Drs. Fellman and Grover also look at the episcleral venous flu- id wave to confirm correct iStent placement. After placing an iStent, infuse balanced salt solution in the eye, and "you'll see the balanced salt solution go through the episcleral veins adjacent to the MIGS site. This implies the normally hidden deep scleral collector channels are patent," Dr. Fellman said. He sug- gests a similar technique with the Trabectome, where the balanced salt solution will exit through the open clock hours. A thorough familiarity with anatomy will help in placing the CyPass (Alcon, Fort Worth, Texas) into the suprachoroidal space, Dr. Moster said. "When delivering the CyPass, it has to go in smoothly," she said. "It's not in anyone's interest to move it around because you don't want to create a large cyclodialy- sis cleft. If that happens, you may create a hypotonous situation." For the CyPass, she suggests following the curve of the globe to avoid extra manipulation. All the suprachoroidal devices are "a little simpler to place" because the anatomy is somewhat easier to identify compared to when the trabecular meshwork is involved, Dr. Sheybani said. Surgeons can "go to the edge of the angle, where the It is equally important to know where the trabecular meshwork is. "The trabecular meshwork doesn't have to be pigmented," said Arsham Sheybani, MD, assistant professor, Washington Universi- ty School of Medicine, St. Louis. "You're looking for almost a translu- cency behind pigment if it's lightly pigmented. The best identifier is to start at the ciliary body band and work your way up to spur and then find the trabecular meshwork right there." Schlemm's canal is much easier to identify when angles are moder- ately pigmented, said Steven Vold, MD, in private practice, Rogers, Arkansas. "In eyes with multiple pigment lines, the corneal wedge visualiza- tion technique at the slit lamp is useful in identifying Schwalbe's line and the pigmented trabecular mesh- work. Also, in both pigmented and non-pigmented eyes, creating a state of hypotony during incisional sur- gery is helpful in identifying angle landmarks due to the influx of blood into Schlemm's canal," he said. If the pigment is limited, Dr. Fellman said to lower pressure "so you can see that flash of blood com- ing into the canal. That will instant- ly identify the spot you need." highly touted website that provides "an excellent anatomical review for the novice MIGS surgeon," Dr. Bacharach said. (For more on gonioscopy and specific lenses, see "Gonioscopy's role in MIGS" in the December 2016 issue of EyeWorld.) Certain MIGS devices "require an intimate knowledge of the angle: the iStent [Glaukos, San Clemente, California], the Hydrus [Ivantis, Ir- vine, California] and the dual blade, the Trabectome [NeoMedix, Tustin, California] and gonioscopy-assisted transluminal trabeculotomy [GATT]. You need to know where you are and where you're incising," said Davinder Grover, MD, Glaucoma Associates of Texas. Poor visualization will adverse- ly impact outcomes. For instance, patients with heavy pigmentation or a deep chamber have more readily identifiable structures compared to patients with shallow or convex irides. Dr. Bacharach and Marlene Moster, MD, attending surgeon, Wills Eye Hospital, Philadelphia, credit Reay Brown, MD, with popu- larizing the use of a staining solu- tion to stain the angle structure. "Stain the capsule early in the procedure, and that will help iden- tify where to place an implant," Dr. Moster said. Experts offer advice on how to ensure devices are placed correctly M icroinvasive glaucoma surgery (MIGS) is an overarching term for a means to improve flow into the canal and collector systems, thereby decreasing IOP levels in patients with mild or moderate glaucoma. Most of these procedures are performed sequen- tially with cataract surgery. Unlike traditional filtration surgery, in MIGS there are no visible markers to confirm there's improved collector channel flow, said Ronald Fellman, MD, Glaucoma Associates of Texas, Dallas. Before MIGS, "many surgeons— comprehensive ophthalmologists and glaucoma specialists alike— hadn't worked in the angle, and some of these cases can be more challenging than others in identify- ing the correct positions," said Jason Bacharach, MD, North Bay Eye Associates, Petaluma, California. To ease the challenge these cases present, Dr. Bacharach recommends "reviewing the anatomy before you head into the OR." Gonioscopy.org, developed by glaucoma specialist Wallace L.M. Alward, MD, is a Pearls for performing MIGS procedures iStent superficially placed in the angle; microforceps are used to reposition the stent in the canal. Source: Arsham Sheybani, MD

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