BLOG: Not all MIGS, and their benefits vs. risks, are created equal

BySavak Sev Teymoorian, MD, MBA

The landscape of glaucoma therapy, in particular surgical, is rapidly changing. It was not that long ago we were introduced to the Glaukos iStent for use as a MIGS. Now with the iStent taking a position in the foreground of surgeons and their practice of patient care, our focus will soon be turning to the next wave of products in the pipeline for minimally invasive surgery. One of the most valuable pearls I learned during my business training is that successful people are able to look at the horizon in the landscape they work in to see what the environment will be like in order to position themselves in that setting.

Currently when we think of MIGS, it centers on the iStent as that is the only FDA-approved product in the space. Other procedures and newer approaches to older surgery are attempting to associate themselves in this area, including surgeries involving Trabectome (NeoMedix), gonioscopy-assisted transluminal trabeculotomy, Trab360 (Sight Sciences), Kahook Dual Blade (New World Medical), ABiC (Ellex) and endoscopic cyclophotocoagulation (Beaver-Visitec International), to name a few. To add to these, there are other but more traditional MIGS products approaching approval for use, including Hydrus (Ivantis), CyPass (Transcend/Alcon), iStent Supra (Glaukos) and Xen (AqueSys/Allergan). The landscape for glaucoma therapy is headed to one that is filled with a plethora of options. The most important issue for surgeons will be how to incorporate these procedures in patient care to maximize outcomes and patient quality of life. In other words, what order should we take to these MIGS? The answer lies with understanding the relative benefit-vs.-risk ratio of each procedure.

The best way to understand how to proceed in that complex environment is to take a step back and understand the differences among these MIGS as they are not created equal. The most important varying characteristic is the anatomical target with each. All of these can be divided into three classes: trabecular bypass/Schlemm’s canal (iStent and Hydrus), suprachoroidal (CyPass and iStent Supra) and subconjunctival (Xen). The first determining factor for use, of course, is simple because we are limited to what is approved for use at the moment. However, assuming all of these are eventually are approved for use, the decision tree for treatment will be influenced by the relative benefit vs. risk of each procedure. All of these are considered MIGS; however, their benefit-vs.-risk ratios will inherently be different because the procedural steps will vary based on the product. The greater the benefit vs. risk, then the earlier it will be used in the treatment tree. There are also two other factors that will need to be considered. The first is will the procedure be approved with an indication at the time of cataract surgery. The second is what, if any, effect will they have on the surgeon being able to still do the gold standard glaucoma procedures with trabeculectomy and tube shunts.

It will be very interesting to see how all this will play out. Based on primary information, one could forecast that the selection of MIGS procedures will go from trabecular bypass to suprachoroidal to subconjunctival. There are many factors that lead to this decision tree, but the general rationale could be the following. With first mover advantage created by iStent, then the trabecular bypass will be used first with iStent or Hydrus. These procedures also keep the surgeon in a space seen during cataract surgery under gonioscopic view. They also would have the highest benefit-vs.-risk ratio and don’t use up conjunctival tissue.

Once the area of greatest resistance to natural aqueous flow (the trabecular system) is bypassed and the patient still needs more IOP control, then the attention will turn to other routes of aqueous diversion. The decision will need to be between suprachoroidal vs. subconjunctival. Since one of the important steps in any glaucoma surgery is preservation of conjunctival tissue to be used for possible gold standard surgery with a trabeculectomy or tube shunt, then suprachoroidal procedures will be next. Another factor that would place suprachoroidal before subconjunctival would be the complicating factor of having to use mitomycin C in the latter. The suprachoroidal options will involve the selection between CyPass and iStent Supra.

Then when the first two targets are used and if further IOP lowering is needed, then attention will turn to surgeries involving conjunctival tissue. Between performing MIGS with Xen or trab/tube shunt, the benefit-vs.-risk ratio would favor Xen and as such would be considered next-line therapy. Once all these spaces are exhausted, then surgical intervention would turn to traditional trabeculectomy or tube shunt.

We are about to enter a new era of rapidly progressing glaucoma therapy with varying benefits vs. risks. The challenges of keeping up and integrating new procedures will ultimately help benefit our patients in maintaining as high of a quality of life as possible. The important issue is to remember each patient is a unique puzzle with different characteristics that will benefit from both specialized and individualized care that can be offered in this evolving period of care.

Disclosure: Teymoorian reports he is a consultant for Glaukos and Allergan.