Appropriate niche sought for minimally invasive glaucoma surgery

Surgeons around the world are adopting minimally invasive glaucoma techniques to implant a growing array of devices designed to facilitate aqueous outflow and reduce IOP.

“I define [minimally invasive] glaucoma surgery (MIGS) as all the procedures that are performed through a self-sealing corneal tunnel less than 2 mm in width. Practically, these include all gonioscopic procedures,” Marco Nardi, MD, OSN Europe Edition Board Member, said. “These procedures are well-accepted by patients with no comparison with conventional filtering procedures. I have some patients that have experienced both types of procedures, and they are enthusiastic about MIGS.”

Trabeculectomy ab interno with the Trabectome and canaloplasty, a more involved ab externo procedure, are both used by surgeons around the world.

Some surgeons combine microincision cataract surgery and MIGS in select cases, while others think phacoemulsification alone is sufficient to reduce IOP in mild to moderate glaucoma cases.

Marco Nardi, MD, performs a combined procedure, cataract surgery with implantation of the Ex-PRESS mini shunt. He said minimally invasive glaucoma procedures have many advantages, including good patient satisfaction. Image: Nardi M

In glaucoma treatment, many surgeons have embraced microincisions and ab interno filtering and bypass devices because they reduce complications, E. Randy Craven, MD, said.

“Minimally invasive glaucoma surgeries evolved because we were trying to get away from problems associated with full-thickness filtering procedures that we have seen for years, which are hypotony, choroidal hemorrhage, bleb problems and things such as that,” he said. “We are seeing that these are newer ways of trying to avoid problems we’ve had with trabeculectomies in the past.”

Safety and efficacy

Dr. Nardi performs procedures with the iStent micro-bypass implant (Glaukos), the CyPass micro-stent (Transcend Medical) and the Hydrus intracanalicular implant (Ivantis). He said benefits of the procedures include less trauma, faster recovery comparable to phacoemulsification, no inflammation and minor complications.

“These procedures are safer than conventional filtering surgery,” Dr. Nardi said. “Usually there is some bleeding in the angle, which in the case of incannulation of Schlemm’s canal is a confirmation of the right placement of the device, but normally it will reabsorb in 1 day to 2 days without sequelae.”

Another benefit is that MIGS procedures do not alter the conjunctiva, allowing for subsequent filtering surgery if necessary, he said. In addition, some of the procedures have a short learning curve.

All these gonioscopic procedures lend themselves well to combined cataract and glaucoma surgery, Dr Nardi said.

Treatment with the Trabectome (NeoMedix) is an alternative to trabeculectomy, the gold standard for cases in which IOP in the mid-teens is an acceptable goal, Steven D. Vold, MD, and colleagues said in a study published in Ophthalmic Surgery Lasers & Imaging in 2010.

The procedure involves insertion of the Trabectome through a clear corneal incision.

Thomas W. Samuelson, MD, OSN U.S. Edition Glaucoma Section Editor, said that while Trabectome surgery is easier to perform, it is less efficacious.

Thomas W. Samuelson

“I don’t have head-to-head data to support that statement, but I think if you look at the data that have been published on both procedures, canaloplasty trumps Trabectome in terms of efficacy,” Dr. Samuelson said. “There’s a price to pay for the efficacy, and that’s the fact that it’s a much more labor-intensive procedure, at least intraoperatively. It is certainly a much longer procedure by several-fold. It requires conjunctival and scleral dissections. And it is a more nuanced procedure and very surgeon- and technique-dependent. But it can be learned, and it’s a really good operation to have available for select patients.”

Canaloplasty (iScience), which involves the use of a suture to stretch the trabecular meshwork and promote the outflow of aqueous fluid, is more suited for patients with advanced glaucoma short of end-stage disease, Dr. Samuelson said. It is also preferable for patients with extreme axial length, high myopia and severe ocular surface disease, which entails an elevated risk of bleb infection, he said.

“I would say canaloplasty is minimally invasive in a different sort of way,” Dr. Samuelson said. “It’s certainly not minimally invasive in terms of how much dissecting you do. In fact, you do a lot of dissecting. But it is minimally invasive in that it’s putting the patient at less risk and it’s basically a nonpenetrating procedure. So, it’s minimally invasive in that sense.”

Indications and contraindications

Typically, the primary indication for MIGS is early to moderate open-angle glaucoma, Dr. Craven said.

“Most of these MIGS procedures have to have open angles,” he said. “Whether or not it has exfoliation or is pigmentary, I don’t know if we have that sorted out yet. But open angle is the main indication.”

MIGS devices are typically contraindicated in patients with advanced glaucomatous damage, previous trabeculectomy or tube implantation, Dr. Craven said.

Candidates for MIGS tend to be active adults with high expectations, according to Dr. Craven.

“I see a lot of people … who love to be up in the mountains, and if they have blebs, their eyes bug them. So, they want to have something else done,” he said.

Good candidates also include high myopes, patients on anticoagulant medication and cataract patients with IOP well-controlled by medications, Dr. Craven said.

A patient with a bleb in one eye who has to undergo glaucoma surgery in the fellow eye but does not want another bleb is also a suitable candidate for MIGS.

E. Randy Craven

“If you can try a less invasive procedure that doesn’t leave them with a bleb, I think the patients really are interested in something like that. It kind of fits into that category that we’re looking for,” Dr. Craven said.

The main indication for the Trabectome is significant cataract with concomitant glaucoma that is not severe enough to warrant trabeculectomy, tube shunt implantation or canaloplasty, Dr. Samuelson said.

Cataract extraction alone is a viable alternative to the Trabectome, as is laser endocyclophotocoagulation (ECP), Dr. Samuelson said.

“I guess one comparator you might make to Trabectome is ECP,” he said. “Some people are ECP enthusiasts. Some people use ECP in that same fashion that others use Trabectome.”

Contraindications for the Trabectome include significant peripheral anterior synechiae resulting from angle closure, Dr. Samuelson said.

“Although typically Trabectome is performed before phacoemulsification, in someone with a shallow anterior chamber, you would probably do it after the cataract is removed just to open the angle up a bit more,” he said. “But it can’t really be effectively done in a patient who has significant synechial closure to the angle. You might not want to do it in patients with elevated episcleral venous pressure, but those cases are pretty infrequent.”

Dr. Vold reiterated that MIGS procedures such as Trabectome and iStent are best suited to patients with mild to moderate open-angle glaucoma.

“I think the predominant patient group tends to be the more mild to moderate open-angle glaucoma,” he said. “Now, can you use them in more advanced glaucoma? I think that’s probably true, but I think the target population is generally mild to moderate open-angle glaucoma.”

Canaloplasty is generally indicated for patients with moderate open-angle glaucoma, according to Dr. Vold.

“When I use canaloplasty, it is generally for people with moderate open-angle glaucoma who tend to be on one to three medications,” he said.

It is possible to use canaloplasty in patients who are on up to four medications, but it is not ideal for patients with blebs, Dr. Vold said, adding that canaloplasty combines nicely with cataract surgery.

Other devices

Dr. Nardi said more long-term follow-up is needed for all the devices, but they could become vital in glaucoma surgery in the future.

“I think that these procedures, once their validity is assessed, might become the first choice in glaucoma surgery. These considerations also give me some enthusiasm about early surgery. I think that, in the near future, the algorithm of treatment may be the following: 1) reopen physiological pathways; 2) gonioscopically entering the suprachoroidal space; 3) filtering procedures (with preference for Ex-PRESS and releasable sutures); 4) tubes,” he said.

The iStent, the first ab interno micro-bypass implant for glaucoma, is designed to fit into Schlemm’s canal.

Dr. Vold said the iStent provides rapid postoperative visual recovery and IOP reduction. It is not uncommon in his hands for patients to have 20/20 vision and an IOP of 10 mm Hg on the first day postoperatively, he said.

“These eyes look remarkably quiet. There’s hardly any tissue trauma. If you use multiple stents, a lot of times you get pressures in the mid-teens or better. I really think that there are some real possibilities with this procedure,” Dr. Vold said.

Steven D. Vold

The Ex-PRESS (Alcon), a mini-shunt implanted between the inner and outer regions of the eye, is designed to bypass the eye’s natural drainage structures.

In an article published in OSN in 2008, Dr. Samuelson characterized the Ex-PRESS mini-shunt as a safe and standardized sclerostomy procedure with a short learning curve.

The AquaFlow drainage device (STAAR Surgical), a collagen implant, is inserted during a nonpenetrating deep sclerectomy procedure. It is designed to channel excess aqueous fluid from the eye. The Hydrus is inserted through a microincision and designed to create an opening through the trabecular meshwork and dilate Schlemm’s canal to facilitate the exit of aqueous fluid. The CyPass is inserted into the eye during routine cataract surgery, after the IOL has been implanted. However, it is still in early stages of use.

The Hydrus implant covers 8 mm of Schlemm’s canal, while the iStent covers 1 mm of the canal, Dr. Samuelson said. Consequently, more than one iStent may be required to achieve more than modest IOP reduction, he said.

“The first Hydrus that I put in [was] 15 mm in length,” Dr. Samuelson said. “So, you get some sense of how much longer that is. The added length adds complexity to the procedure, and 15 mm was too long; 8 mm (the length of the current Hydrus device) seems to be just about right.”

The CyPass and third-generation iStent are inserted into the suprachoroidal space, Dr. Samuelson said.

Dr. Nardi said all the devices offer the potential to be safe alternatives to more devastating filtering surgery.

“In my experience, the surprising thing is that these procedures do not have severe complications; also, in the worst case of a mistake, if you put a device in the ciliary body, it will not function, but it seems to be well-tolerated,” he said. – by Erin L. Boyle and Matt Hasson

References:

Gedde SJ, Herndon LW, Brandt JD, Budenz DL, Feuer WJ, Schiffman JC. Surgical complications in the Tube Versus Trabeculectomy Study during the first year of follow-up. Am J Ophthalmol. 2007;143(1):23-31.

Gedde SJ, Schiffman JC, Feuer WJ, Herndon LW, Brandt JD, Budenz DL. Treatment outcomes in the tube versus trabeculectomy study after one year of follow-up. Am J Ophthalmol. 2007;143(1):9-22.

Shingleton, BJ, Wooler KB, Bourne CI, O’Donoghue MW. Combined cataract and trabeculectomy surgery in eyes with pseudoexfoliation glaucoma. J Cataract Refract Surg. 2011;37(11):1961-1970.

Tham CC, Li FC, Leung DY, Kwong YY, Yick DW, Lam DS. Microincision bimanual phacotrabeculectomy in eyes with coexisting glaucoma and cataract. J Cataract Refract Surg. 2006;32(11):1917-1920.

Vold S, Dustin L; Trabectome Study Group. Impact of laser trabeculoplasty on Trabectome outcomes. Ophthalmic Surg Lasers Imaging. 2010;41(4):443-451.

For more information:

E. Randy Craven, MD, can be reached at Specialty Eye Care, 11960 Lioness Way, Suite 190, Parker, CO 80134, U.S.A.; +1-303-794-1111; email: ercraven@glaucdocs.com.

Marco Nardi, MD, can be reached at Università di Pisa, Dipartimento di Neuroscienze, Via Roma 67, 56126 Pisa, Italy; +39-050-553431; fax: +39-050-992976; email: marco.nardi@med.unipi.it.

Thomas W. Samuelson, MD, can be reached at Minnesota Eye Consultants, 701 E. 24th St., Suite 106, Minneapolis, MN 55404, U.S.A.; +1-612-813-3628; email: twsamuelson@mneye.com.

Steven D. Vold, MD, can be reached at Boozman-Hof Regional Eye Clinic, 3737 West Walnut, Rogers, AR 72756, U.S.A.; +1-479-246-1700; email: svold@cox.net.

Disclosures: Dr. Craven is a consultant for and receives research support from Glaukos, Ivantis and Transcend Medical. Dr. Nardi has received some travel reimbursement from Transcend Medical and is taking part in a clinical trial with Hydrus. Dr. Samuelson is a consultant and investigator for Glaukos and Ivantis. Dr. Vold is a consultant for AquaSys, Glaukos, iScience and Transcend Medical.

 

Should MIGS be considered for glaucoma patients before more invasive surgery such as trabeculectomy or tube shunts?

Surgery should be considered early in disease process

Brian A. Francis

The traditional glaucoma treatment paradigm consisted of medication, followed by laser trabeculoplasty and then external filtration surgery as a last resort. As such, the majority of patients undergoing glaucoma surgery had advanced optic nerve damage and visual field loss. MIGS procedures — canaloplasty (iScience), Trabectome (NeoMedix) and iStent (Glaukos) — were developed to enhance internal filtration via Schlemm’s canal and the collector channels while decreasing some of the more serious risks associated with filtration surgery, such as hypotony, choroidal effusion or hemorrhage, and endophthalmitis. The goals of these procedures are to lower IOP to physiologic levels while reducing dependence on glaucoma medications. Thus, they are not meant to replicate the IOP lowering of filtration surgery and are aimed at a different glaucoma population. The ideal candidate for MIGS is a patient with mild to moderate glaucoma damage, high baseline IOP and a target in the mid teens.

Concurrent cataract extraction, rather than being a risk for failure such as with trabeculectomy, can increase the efficacy of MIGS. If we shift our treatment paradigm to include surgery earlier in the disease progression rather than waiting as a last resort, then current and future MIGS procedures will become a preferred choice for most glaucoma patients.

Brian A. Francis, MD, is a surgeon at Doheny Eye Institute, University of Southern California, Los Angeles, U.S.A. Disclosure: Dr. Francis is a consultant for NeoMedix.

Clinical setting should dictate treatment strategy

Douglas J. Rhee

In general, I think we should move away from thinking algorithmically that there is one particular procedure, whether it be trabeculectomy or any one of the MIGS procedures, that should be used in all cases following failure of medical or surgical treatment. I believe that the literature is beginning to show that different procedures work optimally in different clinical settings. We should move toward having the specific clinical setting dictate which procedure we should use, whether it be trabeculectomy, tube shunt or any of the new MIGS procedures.

Douglas J. Rhee, MD, is an OSN U.S. Edition Glaucoma Board Member. Disclosure: Dr. Rhee has no relevant financial disclosures.