The wonderful world of MIGS

As MIGS devices multiply, so does confusion among surgeons.

The term “minimally invasive glaucoma surgery” (MIGS) was coined in 2009 by Dr. Ike Ahmed. I am sure he had no idea of the door he was opening when he bestowed that catchy name on it — for MIGS has already changed dramatically from its initial state. MIGS has progressed from one or two devices to many devices that attack different areas of outflow.

The problem for us as ophthalmologists is that we are victims of paralysis by analysis — while we have many MIGS options for each different patient type, how does one become comfortable placing or using these devices without studying and researching each one? And how do we do that without becoming overwhelmed? Read on for my attempt to eliminate the confusion.


Before you embark on the quest for the perfect device, the first question you need to ask yourself is, “Do I like taking care of surgical glaucoma?” Yes, MIGS has made this easier and safer, but one must assume inherent risks when performing MIGS.

Patients require more follow-ups and more questions to be answered. Occasionally, mild glaucoma ends up with choroidal folds. Routine cataract surgery that has blood reflux for the first two weeks and blurry vision now becomes a thorn in the flesh.

If you comanage patients, make sure your comanagement teams understand to refer patients back to you immediately when things seem abnormal. Also, expect more phone calls from the referring doctors for problems that you do not see as often with cataract surgery alone. Discussions with your comanagement teams should also discuss guidelines for when to reduce drops after surgery vs. when to be concerned about IOP spikes. Lastly, you will need to educate your local optometric friends on the many new MIGS devices that they may not know about as well as current therapies. These discussions will make your practice and patients much happier.


Next, you will want to start with procedures that have a shorter learning curve and learn them well. Don’t start with the more complicated options first. Also, don’t start with the worst of the glaucoma patients. A good patient to start with is a patient with an open angle and a pigmented trabecular meshwork who you can visualize easily.

I recommend starting with canal-based MIGS due to its ease of use. The Kahook Dual Blade (New World Medical) or the iStent inject (Glaukos) are both forgiving devices for those just starting out. The former leaves behind no hardware in the eye, and the latter leaves behind microscopic stents. Neither are difficult, but without proper understanding of the procedures, the devices can become frustrating.


I typically advise surgeons who are naïve to MIGS to first learn — and master — intraoperative gonioscopy so that they can learn the basics first. You can accomplish this by practicing on patients who are in your normal cataract routine day. You need to become comfortable breaking the tape you have on the patient’s head, tilting the head away from you, rotating your microscope toward you and holding the gonioprism in your hand. If you don’t have a microscope that automatically rotates, this process alone can be burdensome for both you and your staff.

At the risk of sounding as if I’m oversimplifying: Without practicing intraoperative gonioscopy, you will fail at MIGS … miserably.

The issue isn’t performing the intraoperative gonioscopy only, though. The problem is being able to visualize the space you need to see when the device is in the eye and the chamber begins to collapse. The chamber collapses because you will not realize you are lifting on your incision or you are depressing when you first start out. This is why it is critical to use a larger/wider secondary instrument to practice this, so you truly know how much viscoelastic will burp out of your main incision.

The second problem becomes when the patient moves and jerks his/her head that is now not taped. If you are skilled at seeing and viewing the angle well, these distractions from the patient will not affect you as much. You will also want to be prepared to know how to refill viscoelastic in the tilted head position easily. Practice your positioning and refilling viscoelastic, both of which will help you avoid rerotating your microscope back and forth repeatedly.

Lastly, if you do not operate with much magnification, you must learn to do so. MIGS is much easier with good magnification. The issue is that you will need to learn that small movements seem very big with the higher magnification. I recommend that you practice gonioscopy with good magnification to make it as real as possible before starting.

Once you are comfortable with each of these factors, the procedures do not cause much distress. (For more on gonioscopy, see “Using MIGS: Not just for glaucoma specialists,” page 20).

Gonioscopy in action. Practicing intraoperative gonioscopy will help with your MIGS success.


This brings me to the next process: How to choose a device. This is clearly one of the more difficult things to do. Certainly, there are no shortage of devices.

You have trabecular outflow devices or procedures: Kahook Dual Blade (New World Medical), goniotomy, iStent inject (Glaukos), OMNI Surgical System (Sight Sciences), Hydrus (Ivantis), GATT and Trabectome (NeoMedix).

Then, you had a suprachoroidal device: Cypass (Alcon). I want to mention that Alcon pulled Cypass in August 2018 due to safety concerns. We should applaud Alcon for doing the right thing for patient care, but surgeons lost a device that worked well for many people and helped many patients come off of eye drops.

Next, you have aqueous production inhibitors: endoscopic cyclophotocoagulation (Endo Optiks) and MicroPulse P3 Cyclophotocoagulation G6 (Iridex).

Lastly, you have the subconjunctival space: Xen (Allergan) — while it is certainly debatable if the Xen is MIGS, for the sake of this article, we are including it in our consideration.

Currently, these are the devices for MIGS that surgeons have at their disposal, and some guidance is certainly in order. My recommendation when starting out is to choose a device that is not too expensive on the front end for your surgery center, has a high safety profile and can easily be performed on your first few patients. I would start with the canal-based procedures and progress to others as you grow comfortable (see “MIGS pearls,” below).

MIGS pearls

  • RISK MANAGEMENT. Isn’t it fun to be a hero? This isn’t the time. Don’t use the more complicated devices for mild glaucoma. Risk-stratify the severity of the patient’s glaucoma, and formulate your plan of attack. For a patient who has mild glaucoma and takes one drop at night, I use the simple, near risk-free devices rather than risk giving that patient choroidal folds and permanent maculopathy. Don’t try every new device; find what works for you, and use that on the mild glaucoma patients.
  • PRACTICE. Never take practice for granted. You must practice your gonioscopy — and you must be diligent in how you practice. “Practice like you play” is the old adage, and it is very important in surgery.
  • PHAKIC PATIENTS. Get comfortable with a device or two with patients undergoing cataract surgery in combination with MIGS. Find what you like, and use it consistently. This will get you accustomed to the nuances of the devices. I recommend performing the cataract surgery first, just in case you struggle with the device implantation or the surgical technique. If you struggle and then need to abort, at least you will have performed your cataract surgery. Once you become proficient at the MIGS procedure, you can consider doing that first for a clearer cornea.
  • PSEUDOPHAKIC PATIENTS. There are only so many devices for this group (ECP [Endo Optiks], the OMNI system [Sight Sciences], Trabectome [NeoMedix], Kahook Dual Blade [New World Medical] and Micropulse P3 [Iridex]), but these are the patients who need MIGS more than anyone. These patients are on drops and worsening, but selective laser trabeculoplasty will not assist them much. In the past, we went to trabeculectomy for such patients. Now we can offer them a surgery that is not difficult to perform and offers little risk. I go to MIGS quite early in pseudophakic patients whose condition is worsening on two drops.
  • OPHTHALMIC VISCOSURGICAL DEVICES. Use something that you feel will hold the anterior chamber well. Healon (AMO), Healon GV (AMO), Amvisc (B + L), Amvisc Plus (B + L) and Provisc (Alcon) are ideal options because they are cohesive.
  • HEAD TILT. More is often better. If you know a patient is not going to be able to turn his or her head, I would stay away. The angle must be visualized well when starting out. Do not cut corners on this process, as it sets up the entire procedure.
  • SCOPE TILT. My suggestion is to operate with the scope tilted toward the surgeon. We don’t tilt our scope at all during MIGS. I simply tilt the patient’s head, which increases efficiency. No staff is needed to help adjust the microscope before, during or after the surgery with this method — we never touch the scope orientation.
  • BLOOD THINNERS. This seems to be a controversial topic. I rarely stop blood thinners, because I do not want to allow for the chance of a stroke the first few days of blood reflux in an attempt to save a patient’s mild glaucoma. However, if you are doing 360-degree angle procedures, it is wise to stop blood thinners. I have certainly had my set of patients with 6-7 mm hyphemas day-one postop. This can be discouraging to a beginner MIGS surgeon, so consider stopping if you are at all concerned.
  • ANESTHESIA. I don’t typically start IVs on my routine cataract patients, but, for MIGS patients, I recommend using IV sedation initially to help with discomfort. You need a comfortable patient who is relaxed, because, if they become distressed, you certainly will.

Please understand that each MIGS device has its own reimbursement challenges. Before you make your decision on which device to use, check with the major carriers in your area as to if you will get reimbursed and how much.


My final word of advice for tackling MIGS: Prepare for frustrations. This is not normal cataract surgery, so begin with the understanding that you will have some struggles early on. However, once you leap those hurdles, you will forever change your patients’ lives.

MIGS has certainly revolutionized glaucoma surgery — we now have so many amazing options to avoid a trabeculectomy. Blindness continues to occur at a rapid rate in glaucoma, but thankfully, with MIGS, we now have a much better chance to destroy our enemy. OM

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