Choosing the Right MIGS Procedure
All glaucoma surgeons should have at least two and possibly more types of minimally invasive glaucoma (MIGS) procedures with different methods of action in their armamentarium, according to Brian A. Francis, MD, a glaucoma specialist at the Doheny Eye Center at UCLA School of Medicine. At a minimum, “you should have at least one procedure that you can do in a phakic or pseudophakic patient that’s not limited to cataract extraction. Trabecular outflow procedures for me are usually first line, but aqueous inflow procedures are very versatile.”
The bottom line: “Always think about what you want to accomplish, what the eye is [allowing you to do], and what the patient wants.”
Glaucoma surgery is basically divided into these four different methods of action, explained Dr. Francis:
- Trabecular outflow procedures, including Schlemm’s canal dilation, trabecular stents, and trabecular removal or trabeculotomy/goniotomy.
- Suprachoroidal outflow, which is combined with cataract extraction and makes use of the suprachoroidal or supraciliary space and uveal scleral outflow.
- Aqueous humor production. This includes endoscopic cyclophotocoagulation (ECP), which is titratable can be done with or without cataract extraction and done either via an anterior approach or pars plano approach. “It has utility in mild glaucoma all the way to ultra-refractory glaucoma.” Transscleral cyclophotocoagulation also falls in this category.
- Subconjunctival outflow procedures. “I call these less invasive glaucoma surgeries, since you do have a bleb and mitomycin application [is required].” These are divided into ab interno and ab externo approaches.
How to Choose
How do you choose which procedure? Dr. Francis suggested asking yourself the following five questions:
- Is there a coexisting cataract?
- What’s the diagnosis, as well as the anatomy of the eye?
- What is the target intraocular pressure (IOP)?
- What medications can the patient use?
- What is the patient’s preference and how does his or her lifestyle impact the choice?
Coexisting cataract. Keep in mind that all MIGS devices are currently approved only with cataract surgery. Additionally:
- Consider MIGS with cataract surgery even if the patient is well-controlled but on multiple medications. The goal is to reduce the glaucoma medication burden.
- While angle closure glaucoma might improve with cataract surgery alone, it might require a MIGS procedure along with it.
- Endoscopic cyclophotocoagulation (ECP) is difficult in a phakic eye; it has to be done either with cataract surgery or in an eye that is pseudophakic.
Diagnosis and anatomy. Consider these best practices:
- Primary open-angle glaucoma (POAG): All MIGS procedures can be considered for these patients.
- Exfoliation glaucoma: Since trabecular outflow is the main problem in these individuals, consider one of the procedures that targets trabecular meshwork–either a stent procedure or removal of trabecular meshwork. ECP is difficult to perform in those with severe disease.
- Pigmentary glaucoma. Use the same approach as with exfoliation glaucoma, targeting trabecular outflow.
- Narrow angle glaucoma. Combine cataract extraction with MIGS procedure if possible. Use caution if leaving an implant in the angle. Make sure that it’s not large enough to cause problems with the cornea.
- Chronic angle closure glaucoma. Consider MIGS plus goniosynechialysis, aqueous inflow procedures, or subconjunctival procedures.
Target IOP. Expect the following:
- Angle based surgeries: 14 to 17 mmHg
- Suprachoroidal outflow: 13 to 15 mmHg
- Aqueous inflow procedures: Expect a 30% reduction
- Subconjunctival filtration surgeries: 10 to 14 mmHg
“It is possible to combine procedures for greater efficacy in those patients with lower target pressure,” said Dr. Francis. Keep in mind that “patients who are intolerant to medications will likely require a more aggressive procedure.”
Francis B. How do I choose the right MIGS? Talk presented at: AAO 2018 annual meeting; October, 26-30, 2018; Chicago.