Multiple surgical approaches needed to adequately address glaucoma
Minimally invasive glaucoma surgery techniques have been an invaluable addition to the armamentarium of glaucoma management. Many options are currently available, but there are no hard and fast guidelines for surgeons to choose between options.
“It can be quite confusing. Where do we start? How do we choose between options and why? How do we select the best MIGS for each patient?” OSN Glaucoma Board Member Ike K. Ahmed, MD, FRCSC, said.
“What we know for sure by now is that there is some benefit in lowering pressure without topical medications. That’s why we are moving toward surgical intervention. The challenge is safety, and MIGS have allowed us to address safety,” he said.
While the search for the best solution is ongoing, surgeons need to establish their own criteria, based on the best available data and experience.
“We are still on the journey and the perfect surgical procedure has not been created, but we are working to achieve that goal,” Marlene R. Moster, MD, of Wills Eye Hospital, said.
Which MIGS for which surgeon?
In 2020, every cataract surgeon should give consideration to learning and adopting at least one MIGS procedure for cataract patients with glaucoma, according to Healio/OSN Board Member Nathan M. Radcliffe, MD.
“There is now not only an overwhelming amount of evidence but some of the highest-quality evidence ever measured in glaucoma that shows that adding MIGS can enhance the pressure-lowering and medication-reduction ability of cataract surgery without adding any significant safety problem. So to begin with, cataract surgeons should adopt MIGS, and from there, all the choices are ahead of them,” he said.
Stenting is a good place to start because it is safe and relatively easy, provided that the surgeon is properly trained in the visualization and positioning of the stent, according to Ahmed.
“The biggest challenge is visualization and positioning, while the actual procedure, whether stenting or cutting, is not typically a major barrier. The iStent inject (Glaukos), for instance, is quite user-friendly and has a short learning curve. When you get more advanced, you can start going to larger stents like the Hydrus (Ivantis) and eventually try some of the trabeculotomy approaches,” he said.
Subconjunctival stent procedures such as the Xen (Allergan) and InnFocus (Santen) are typically more reserved for the glaucoma specialist who is already acquainted with ab externo approaches, such as trabeculectomy and tube shunts, and with managing a bleb.
“For experienced glaucoma surgeons, it will be a seamless transition, though the Xen does require some learning curve,” Ahmed said.
Combined and stand-alone surgeries
Both the iStent and the Hydrus are only approved in the United States in combination with cataract surgery, but they are well on their way to generate data in support of stand-alone surgery, according to OSN Glaucoma Section Editor Thomas W. Samuelson, MD. In a study, he compared the efficacy of two first-generation iStents vs. Hydrus in an off-label use as stand-alone procedures.
“In this experimental model, Hydrus had a greater influence on outflow facility when used as a stand-alone procedure. Eight millimeters in length, Hydrus occupies the entire intranasal quadrant and may be a viable strategy for a stand-alone procedure in mild to moderate glaucoma. Yet, it is a bigger operation because you are disrupting a little more of the canal than occurs with iStent, but I think you can anticipate a more durable effect when performed without phacoemulsification. In the USA PMA trial, the HORIZON trial, the Hydrus has proven stable efficacy at 3 years, which is unique among the MIGS trials,” Samuelson said.
However, the study showed that both technologies are effective, and he believes that surgeons do not need to apologize if they favor one over the other.
“They are both excellent, and though we don’t use them as stand-alone here in the U.S., our study gives us a glimpse of the future when we’ll have the opportunity to do so. For the time being, I like the elegance of these devices for combined procedures,” he said.
The status of the native lens is one of the first things Samuelson looks at to determine the next step in the management of patients with glaucoma. If patients are phakic and have a cataract, it is easy to decide what to do next, specifically combined surgery with a MIGS procedure.
“If they are pseudophakic, I believe there is a nice place for the incisional procedures, such as excisional goniotomy with the Kahook Dual Blade (KDB, New World Medical), gonioscopy-assisted transluminal trabeculotomy (GATT) and the Omni glaucoma treatment system (Sight Sciences). I perform GATT with Omni a fair amount as a stand-alone procedure for my higher-risk patients who are not good candidates for transscleral surgery. Some surgeons favor KDB, which has the added benefit of eliminating the trabecular tissue rather than just incising it, although the goniotomy is more segmental than with GATT,” Samuelson said.
Type and stage of glaucoma
According to Moster, the main criteria for choosing between MIGS procedures are the visibility and viability of the angle, how long the patient has had glaucoma and what type of glaucoma they have. The patients she prefers for the majority of MIGS have mild to moderate glaucoma.
“In patients with cataracts, I consider trabecular bypass surgery like the iStent or iStent inject in an effort to eliminate one or two of the medicines. If I can lower the pressure by 20% and stop one medication, that is a win-win situation,” she said. “If visual field loss is more than just mild, I am in favor of combining cataract surgery with a Hydrus. I have been pleased with the postop pressure-lowering effect and lack of complications.”
In young patients with a history of juvenile glaucoma or steroid-induced glaucoma and very high IOP, her favorite procedure is GATT. If the patient has pseudoexfoliation, high IOP and has not been on medicines for an extended period, GATT or Omni also work well, she said. However, she warned that if the patient has been on maximum glaucoma medicines for years, the collector channels are usually no longer flexible, and this will hinder the success of angle procedures.
In more advanced glaucoma, when pressure needs to be lowered into the low teens and the conjunctiva is mobile and thin, a Xen gel stent placed either ab interno or ab externo with mitomycin C is potentially a good option.
“However, I do tell the patients that the needling rate is at least 40% and the failure rate is significant. In that case, we will need to move on to a different procedure, either a trabeculectomy or a tube,” she said.
Moster is looking forward to the PreserFlo microshunt (Santen), another bleb-forming device that will possibly replace trabeculectomy.
“I will reserve this for patients who have the ‘real deal’ glaucoma and require an IOP close to 10 mm Hg,” she said.
Staying tuned to all options
Ahmed divides options in three categories to cover different scenarios.
“If I am doing cataract surgery, I often combine it with stenting. If I do a stand-alone procedure and I want to go into the canal, I do ab interno trabeculotomy. If I want more pressure reduction and want a bleb, I typically use subconjunctival microstents and microshunts. Otherwise, I do trabeculectomy when I need to get very low pressure of single digits,” he said.
In his practice, he sees many patients with moderate to advanced disease who need a strong pressure reduction, and therefore he uses the subconjunctival MIGS with Xen and InnFocus.
Although both the iStent inject and the Hydrus are approved in Canada as stand-alone procedures, Ahmed still likes to use stent-free MIGS in patients with no cataract so he can maximize the potential lowering of pressure through the conventional outflow in the canal and trabecular meshwork.
“I feel that I can access a greater part of the eye when using a trabeculotomy approach,” he said.
In some cases, he combines a 90° trabeculotomy with a stent to have the advantages of both approaches.
Selective laser trabeculoplasty also occupies an important place in his armamentarium of glaucoma management.
“I offered it as first line for many years, and the LiGHT study confirmed that it is superior to initial treatment with topical medications in patients with open-angle glaucoma. The benefits in terms of compliance and side effects are valuable for patients. I don’t consider it as a MIGS because we don’t go into the eye, but I do believe that it is a procedure worthy to perform earlier in the disease as first line,” Ahmed said.
He also believes that surgeons should reevaluate excimer laser trabeculotomy.
“The concept has been around a long time but is starting to get more awareness now as a MIGS option, and we should stay tuned to it,” he said.
Cost, coverage and personal preferences
The choice of one MIGS over another can partly be determined by cost and coverage issues, Radcliffe said. Both the iStent and Hydrus are reimbursed using a Category III CPT code, which is covered by Medicare and some, but not all, commercial insurances. MIGS procedures such as KDB, Omni and ABiC (Ellex) are covered by Medicare, Medicaid, PPOs and commercial insurances.
The patient’s perception and risk attitude should also be thoroughly discussed to reach a joint decision.
“Some patients are more comfortable with a big stent in the eye, some patients don’t want any stents, some patients don’t like tissue to be removed, and some patients would rather have tissue removed than a piece of hardware in their eye. Decisions often come out of this kind of dynamic conversation,” Radcliffe said.
Most importantly, the individual skill set of each surgeon can influence the choice.
“I am really good on some of my MIGS, and with others I struggle a little bit. That’s not saying one procedure is easier than another. It is just my experience and skill set and where I am in the learning curve,” he said.
Another piece of advice Radcliffe gives is to “use procedures that you have used in your patients and have worked in your patient population.”
“I practice in New York City and in the Bronx, and I found different approaches work in those two different offices. I have my own data and look at my results to tailor my approach. Look at your own results, at your data, at your own experience,” he said.
After the CyPass storm
Magda Rau, MD, of Augenklinik Cham, Germany, was satisfied with the CyPass (Alcon) and, before the device was withdrawn from the market, did not feel the need to search for another MIGS procedure.
“At the 2019 ASCRS meeting, I presented my own cases of endothelial cell loss at 10 years, mostly due to malposition of the CyPass (41 CyPass eyes, three with malposition and two without). On the other hand, trabeculectomy causes much greater loss of cells. The CyPass was a very elegant and smooth procedure, and the reduction of IOP and medications was very high and stable over more than 5 years. I would appreciate it if it was introduced again for severe cases,” she said.
The alternative Rau uses now is the iStent inject, but she is aware that pressure and medication reduction is not as high as with the CyPass and the effect may not be as long lasting.
“Fibrosis occurs, and due to the very small size of the iStent inject, it is very difficult to intervene with YAG. If patients don’t come to regular examinations, sometimes we find the iStent has disappeared after a couple of years,” she said.
“I have already implanted in four patients the new iStent inject W. This device is even more easy to implant because of the improved injector, and the larger collar promises better visibility and lower fibrosis. The iStent inject is a very elegant, low-risk procedure and is my choice for mild and moderate glaucoma, as a combination but as well as a stand-alone procedure,” Rau said.
She recommended the iStent as well for pseudoexfoliation and pigment glaucoma and for combined procedures.
Another alternative, in more advanced cases that still qualify for MIGS is the dilation of Schlemm’s canal through viscocanaloplasty with the Omni.
“For greater pressure reduction, you can combine it with ab interno trabeculotomy, so you open with the same device two quadrants of Schlemm’s canal,” she said.
“The advantage of the Omni procedure is that trabecular meshwork and Schlemm’s canal are treated circularly in the large whole area,” she said. “The other advantage is that no microstent stays in the iridocorneal angle. I am concerned that endothelial cell loss could be observed in the long term with other microstents.”
Rau does not currently perform Xen surgery but is looking forward to the new PreserFlo to become available.
“It is implanted ab externo and promises the same reduction of the pressure of Xen, which is very high,” she said.
Favor the natural outflow pathway
Samuelson also would like to have the CyPass back for moderate to severe glaucoma cases.
“I always thought it was better utilized in advanced glaucoma because you are creating an alternative outflow pathway. I declined participation in the CyPass as well as the analogous trial sponsored by Glaukos because I felt that for mild to moderate patients I didn’t want to do something as intrusive as creating an outflow into the supraciliary space. Such patients are ideal for canal-based devices,” he said.
Many of the current glaucoma treatment strategies aim at restoring the efficiency of the physiological outflow pathway through the trabecular meshwork and Schlemm’s canal.
“SLT, Rho kinase inhibition, the nitric oxide-donating prostaglandins and our MIGS treatments — all these strategies are targeting the physiological trabecular meshwork outflow because, at the end of the day, it is really beneficial to keep the aqueous inside the eye where it belongs. It sounds like a trite statement, but the aqueous naturally flows within the eye, and keeping the outflow within the eye is the safest strategy,” Samuelson said.
Only patients who do not respond adequately or have glaucoma too far advanced and need the lowest pressures should undergo a procedure that creates external flow such as Xen, trabeculectomy or tube shunts, he said. While the supraciliary strategy is likely safer than transscleral procedures, it still creates an artificial pathway.
The decision whether and when to perform MIGS is based on many factors, including medication adherence and tolerance, IOP reduction, diurnal and nocturnal peaks, visual field and, importantly, the status of the optic nerve and retinal nerve fiber layer, Rau said.
“When in spite of the medications there is damage to the optic nerve, it is clearly a sign that pressure reduction is not satisfactory and that it is time to do a procedure. Now we have the imaging technology that can detect changes of the optic nerve earlier, and MIGS gives us the opportunity to react at the early stages of damage to the optic nerve,” she said.
“I consider SLT first line, medications as first or second line, but when I see a patient who is progressing and not compliant and whose pressure is above 15 mm Hg, for me it is a warning sign. This patient in the long run is at risk, and I don’t hesitate moving on to a MIGS procedure,” Ahmed said.
The beauty of the less invasive strategies is that they can be combined and titrated according to individual needs and work synergistically toward the best control of IOP and glaucoma, according to Samuelson. Medications, in his view, may be reduced but not necessarily excluded when tailoring MIGS strategies to individual patients.
MIGS and meds
“We have much better pharmacotherapy now for glaucoma than we had a few years ago, and that enables us to use the very best of pharma and the very best of MIGS together. I liked the term minimally intrusive sustainable therapy (MIST), but we already have too many acronyms. It is basically a ‘MIGS and meds’ concept. The key is sustainability,” Samuelson said.
MIGS by itself does not have enough efficacy to achieve pressures in the low teens, but if MIGS is used in combination with some of the new more potent drug therapies, this can be a winning combination.
“We can do phacoemulsification with Hydrus or iStent and anticipate continuing prostaglandin therapy maybe with nitric oxide-donating moiety or Rho kinase inhibitors. So, we marry some of the very potent pressure reduction strategies from the pharma side with our MIGS procedures, maximizing the outflow through the canal,” Samuelson said.
In other words, the safe, modestly effective MIGS surgery, which avoids many of the complications of more aggressive surgery, benefits from the concomitant administration of the best currently available drug therapies.
“The idea is to avoid the unrealistic drug regimens that we had in the past and adopt a sustainable minimally intrusive drug schedule,” he said. – by Michela Cimberle
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- For more information:
- Ike K. Ahmed, MD, FRCSC, can be reached at Prism Eye Institute, 2201 Bristol Circle, Suite 100, Oakville, Ontario, L6H 0J8, Canada; email: firstname.lastname@example.org.
- Marlene R. Moster, MD, can be reached at Wills Eye Hospital, 840 Walnut St., Philadelphia, PA 19107; email: email@example.com.
- Nathan M. Radcliffe, MD, can be reached at New York Eye Surgery Center, 1101 Pelham Parkway North, Bronx, NY 10469; email: firstname.lastname@example.org.
- Magda Rau, MD, can be reached at Augenklinik Cham, Cham, Germany, 93413; email: email@example.com.
- Thomas W. Samuelson, MD, can be reached at Minnesota Eye Consultants, 710 E. 24th St., Suite 100, Minneapolis, MN 55404; email: firstname.lastname@example.org.
Disclosures: Ahmed reports he is a consultant for Aerie Pharmaceuticals, Alcon, Allergan, Ellex, ELT Sight, Glaukos, Iridex, Ivantis, New World Medical, Santen and Sight Sciences. Moster reports she is a consultant for Glaukos, Allergan, Santen, Ellex and Iridex. Radcliffe reports he is a consultant for Lumenis, Ellex, Iridex and Beaver-Visitec International. Rau reports no relevant financial disclosures. Samuelson reports he is a consultant for Alcon, Glaukos, Ivantis, Sight Sciences and New World Medical.
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