Which MIGS procedure should one choose for a specific patient?
E. Randy Craven
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Today’s glaucoma surgeons are fortunate to have access to a wide array of procedures that can be tailored to individual patients. As a general rule, procedures with superior safety (e.g. trabecular outflow-enhancing procedures) may be less efficacious in lowering intraocular pressure (IOP) than trans-scleral filtering surgery.
Schlemm’s canal (SC) outflow-enhancing procedures (e.g. trabecular bypass, goniotomy, and canaloplasty) are best considered for patients with an IOP target in the mid to high teens. In addition, those with medically controlled glaucoma and IOP targets in the low teens may reach their IOP goals with trabecular bypass procedures in conjunction with medications. When choosing between different types of trabecular-bypass implants, often the availability of the implant itself may play a role in what device is used; implant availability may be limited by cost and/or insurance constraints. The mechanism causing the glaucoma (secondary glaucoma vs primary open-angle glaucoma), the view of the angle, and the approach to the angle also play a role in procedure choice.
Suprachoroidal implants increase outflow through an alternate route to the SC outflow pathway; they can achieve IOP targets in the teens. The first supraciliary stent approved (CyPassTM, Alcon, Fort Worth, TX, USA) was withdrawn from the market because of concerns related to increased rates of endothelial cell loss in some patients; the rate was higher with a longer length of the implant in the anterior chamber, which would indicate technique of implantation for this this device is critical.
Subconjunctival minimally invasive glaucoma surgery can lead to enough IOP lowering to achieve a target in the low teens. In addition, for those with a low likelihood of the conventional outflow system working, such as those with raised episcleral venous pressure, this option is appealing. The use of the XEN® Gel Stent (porcine gel stent; Allergan, Dublin, Ireland) decreases tissue manipulation, often with improved visual recovery compared to conventional procedures; the technique is evolving. The PRESERFLOTM MicroShunt (Santen, Osaka, Japan) and future smaller shunts currently in development require some tissue dissection, but less than the current tube shunts; these may produce more consistent IOP reduction in patients with prior failed trabeculectomy, as well as in younger, non-white, and diabetic patients. More traditional therapy, such as trabeculectomy, can be employed to achieve very low targets (< 8 mmHg) and tube shunts are useful with neovascular, uveitic, and complex anterior segment issues causing glaucoma.
New Concepts in Glaucoma Surgery Series: Volume 1, pp. 55-66 #3
Edited by: John R. Samples and Iqbal Ike K. Ahmed
© Kugler Publications, Amsterdam, The Netherlands
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