In the past 5 years, there has been an explosion in the number of minimally invasive glaucoma surgery (MIGS) procedures. Duke’s chief of Glaucoma, Leon Herndon, MD, discusses the challenges facing the field, the role of the new techniques, and the future of glaucoma surgery.
Question: What have been some of the biggest challenges in treating glaucoma?
Herndon: There are 2 gold-standard surgeries that have been around for about 50 years. One is trabeculectomy where we’re creating a new drainage outflow pathway for the eye. The other is a glaucoma drainage device where we’re inserting a little silicone tube into the eye to control pressure. Although both procedures can significantly lower intraocular pressure (IOP), they also have the potential for significant complications. For years, there has been an unmet need for a safer alternative, especially for patients with mild to moderate glaucoma, who you might not want to subject to the potential complications of trabeculectomy or glaucoma drainage devices.
Question: How have MIGS helped address this need?
Herndon: MIGS have lower complication rates and shorter recovery times than the traditional surgeries and can be very beneficial for patients with mild to moderate glaucoma. If the MIGS procedure fails, we also still have the option of performing the more traditional surgeries.
The challenge now is patient selection. There are close to 10 different MIGS available, with two additional MIGS technologies likely to be approved this year. These surgical approaches address one of three outflow pathways: trabecular meshwork, suprachoroidal space, or subconjunctival space. We need to learn how to choose the right technology for each patient.
Question: What are some considerations in making that decision?
Herndon: Some decisions are straightforward. For patients with severe glaucoma, the more traditional glaucoma surgeries are still the best choice because MIGS don’t typically reduce IOP to the same extent. For moderate glaucoma, subconjunctival and suprachoroidal MIGS like Xen (Allergan, Dublin, Ireland) and CyPass (Alcon, Hünenberg, Switzerland) may be appropriate because they tend to achieve lower IOP than those that increase outflow by bypassing the trabecular meshwork. We also need to consider the type of glaucoma and the age of the patient.
Right now there aren’t any good guidelines for patient selection; we’re reliant on mostly anecdotal evidence and small studies to help us determine which procedure will be most effective. To address this, our division has started a prospective registry to collect data and to assess outcomes on every patient who undergoes a MIGS procedure at Duke. In a few years, I think we will have developed a good algorithm based on this registry. Ultimately, we may not have as many MIGS available because a few will have risen to the top as the preferred devices for mild to moderate glaucoma.