Mix-and-match approach expands uses for minimally invasive glaucoma surgery
Combining minimally invasive glaucoma surgery procedures is a feasible, versatile alternative for lowering IOP and minimizing the side effects of a surgical approach to glaucoma, according to one specialist.
“The gold standard for lowering IOP in patients who are not well controlled with drops has been traditionally trabeculectomy and in some cases tube shunts. With the advent of MIGS, we are starting to see that we can lower the pressure perhaps not as much as with trabeculectomy, but with much fewer side effects. In addition to that, we have the ability to combine more than one of these MIGS procedures to have an additive pressure-lowering effect,” OSN Technology Board Member David A. Goldman, MD, said.
Currently, there are multiple pathways for lowering IOP in the MIGS space. On one hand, the trabecular meshwork approaches include micro-bypass devices such as the iStent (Glaukos) and the Hydrus (Ivantis) as well as procedures such as canaloplasty (Omni, Sight Sciences) and Trabectome (NeoMedix). Ciliary body approaches, on the other hand, include endocyclophotocoagulation (ECP, Beaver-Visitec International) and MicroPulse transscleral cyclophotocoagulation with the Iridex G6 laser. In the suprachoroidal space, there are the iStent Supra (Glaukos) and the CyPass micro-stent (Alcon). The latter is currently off the market, Goldman said, but he hopes it will return. Finally, the subconjunctival pathway is currently addressed by the Xen gel stent (Allergan).
“We can combine MIGS procedures that target the same pathway, but most physicians would rather address different pathways. For instance, when the iStent first came out, one of the popular treatments was ICE: iStent, cataract and ECP combined together,” Goldman said.
No trial has so far evaluated how MIGS procedures can be complementary to each other. When selecting one or the other of the MIGS mix-and-match options, indications and contraindications must be evaluated.
“If I have a patient with a history of uveitis, I typically stay away from doing ECP. If I have someone with narrow angle, I avoid trabecular meshwork approaches. Furthermore, depending on the insurance profile of the patient, some of these procedures may or may not be covered. I have tried almost every possible combination, with the exception of Xen, which is efficient on its own,” Goldman said.
One of the first combinations to be introduced was ICE. After cataract surgery, once the IOL is in the capsular bag, ECP is performed. The ECP probe is then removed, the patient’s head is rotated to use the gonioprism on the cornea to visualize the anterior chamber anatomy, and the iStent is implanted. Finally, the patient is repositioned to remove the viscoelastic, and the procedure is completed as normal.
“That was probably the first combination that became popular. Since then, I also did goniotomy with Kahook Dual Blade (New World Medical) combined with CyPass and was getting very good outcomes. Now, since the CyPass has been off the market, I tried other combinations with variable success. I tried goniotomy and canaloplasty together, both done with the Visco360 viscosurgical system (Sight Sciences, now replaced by the Omni surgical system). However, if the patient needs significant IOP lowering, I go straight to Xen gel stent,” Goldman said.
Studies have been able to demonstrate that the effect of MIGS procedures is stable over time within IOP ranges that depend on the device used. According to Goldman, the iStent has some of the least efficacy but also the least number of side effects, whereas Xen has the greatest IOP-lowering effect but may require more postoperative manipulation in terms of bleb revision.
“Originally I was very nervous about doing bleb revision; now I really have no concerns. I don’t see it as a big barrier in performing the Xen stent procedure,” he said.
In between these two extremes, every MIGS combination has an added effect in terms of lowering pressure.
“Most commonly right now I do ECP combined with canaloplasty, and this lowers IOP by about 10 mm Hg on average,” he said.
Reducing the burden of medications is an important goal of MIGS surgery. In the best scenario, patients may be completely off eye drops; in the worst scenario, they may have to continue using drops, but IOP should be better controlled.
Goldman said that a common misconception is that every patient should have IOP reduced to 9 mm Hg or 10 mm Hg and be off drops. The reality is that many patients can do well with IOP in the low to mid teens and that simply reducing the number of drops will significantly improve compliance and ocular surface issues over the years.
“The nice thing about combining MIGS procedures is that we can multiply the effect on IOP reduction without increasing the risk profile significantly,” Goldman said.
In other words, there is no added risk other than the risk inherent to the second device that is used.
“When you are entering the Schlemm’s canal with a Goniotome (NeoMedix) and KD Blade and do canaloplasty or trabeculotomy as well, there is always a chance that you can have some blood reflux into the anterior chamber. Some of these cases might also have recurrent hyphema. This will typically resolve in the early postop, but it is certainly one of the risks you have when you are entering the trabecular meshwork,” Goldman said.
Suprachoroidal devices carry the risk of endothelial cell loss, as shown by the COMPASS-XT study with the CyPass micro-stent. Further investigation will clarify whether this is an inherent problem of suprachoroidal shunts or a specific effect of the CyPass.
“The CyPass has been withdrawn from the market, but I think it is important to recognize that trabeculectomy and tube shunt surgery also have their own risk of endothelial cell loss,” Goldman said.
The risk profile of combined procedures should be discussed with the patient, as well as the additional costs involved.
“I tell my patients that what they pay extra will be regained in terms of less money spent in the pharmacy and that fewer drops or no drops will make their life easier, with a better controlled glaucoma and a better ocular surface over time,” Goldman said.
Blurred boundaries between procedures
As MIGS procedures gradually evolve, the boundaries between trabeculectomy and multiple MIGS procedures are likely to become progressively more blurred.
Currently, there is no MIGS procedure or combination procedure that can consistently achieve a single-digit IOP with no medications.
“It is possible but not common and not easy to replicate, so I think that if you have a patient with severe glaucoma that needs a pressure of 9 mm Hg, trabeculectomy is still the preferred option,” Goldman said. “However, not every patient needs a pressure of 9 mm Hg off all drops. A lot of patients would do perfectly well with a pressure of 12 mm Hg or 14 mm Hg, on none or even one drop, and so I think it depends on what the ultimate goal is for each patient.”
As MIGS devices continue to evolve, together with understanding of how the interplay of these devices causes a synergistic lowering of IOP, there are going to be more surgeons moving toward MIGS as a primary surgical approach to glaucoma before performing a trabeculectomy or tube shunt procedure, he said. – by Michela Cimberle
- For more information:
- David A. Goldman, MD, can be reached at Goldman Eye, 3401 PGA Blvd., Suite 440, Palm Beach Gardens, FL 33410; email: email@example.com.
Disclosure: Goldman reports he is a consultant to Glaukos, Alcon, Sight Sciences and Allergan.