Minimally invasive glaucoma surgery increasingly performed by anterior segment surgeons

Anterior segment surgeons are increasingly performing minimally invasive glaucoma surgery in their patients with mild to moderate disease, especially in conjunction with cataract surgery.

“What these procedures have done is brought effective glaucoma surgery into the hands of mainstream cataract surgeons who prior to these procedures did not routinely perform glaucoma surgical procedures,” OSN Technology Board Member Jodi I. Luchs, MD, FACS, said. Moreover, minimally invasive glaucoma surgery (MIGS) “can produce a significant difference in clinical outcomes, reducing intraocular pressure and relieving the need to use topical medications in many cases,” he said.

With anterior segment surgeons embracing MIGS to treat mild to moderate glaucoma, fewer patients would need to be referred to glaucoma specialists for disease progression. As a result, glaucoma surgeons would need to perform fewer heroic procedures on end-stage patients because there would be better control of glaucoma upstream in the disease process, according to Luchs. Patients would also be relieved of the hassle of insurance reimbursement for drops or having to worry about ocular surface problems.

“MIGS can provide more round-the-clock routine pressure lowering without requiring the patient’s input,” Luchs said.

Image: Alfonso J

Advantages of MIGS

Another advantage of MIGS is that patients are not excluded from having another glaucoma surgical procedure later, such as trabeculectomy or tube shunt surgery.

“Hopefully, when these patients arrive at the point where they need more invasive surgery, they will not be in such end-stage condition,” Luchs said, noting that MIGS might even improve the success rate of a subsequent intervention. “MIGS may be an adjunct to the pressure-lowering effect of a later procedure,” he said.

Thus far, the Glaukos iStent, a trabecular micro-bypass stent, is the only FDA approved MIGS device for use in cataract surgery. Normally performed after cataract removal, the iStent procedure involves introducing an inserter through the phaco incision, advancing past the pupillary margin and then viewing the angle under high magnification with a gonioprism. Once the trabecular meshwork is engaged, the iStent is gently advanced into Schlemm’s canal.

Because anterior segment surgeons such as Luchs are not used to routinely performing intraoperative gonioscopy, there is a short learning curve to achieve good visualization of the angle for facilitating insertion of the titanium iStent.

“Even if things do not go well during the first few procedures — such as difficulty in implanting with a few passes, the inability to quite get the device to sit properly and causing a little bleeding — the next day the patients look great and do great,” Luchs, who over the past year has implanted the iStent in tandem with cataract surgery in about 100 patients, said.

“With this type of procedure, there is very little downside, quite frankly. There is very little harm you can cause with this device. This definitely provides you some level of comfort,” he said.

Luchs said there are a number of devices in development that will be implanted in the suprachoroidal space and some, such as the iStent, into Schlemm’s canal but with different designs. The iStent inject (Glaukos) is preloaded with two stents in one applicator, and the Hydrus microstent (Ivantis) is a crescent-shaped stent that dilates open Schlemm’s canal. The CyPass micro-stent (Transcend Medical) and the iStent supra (Glaukos) both drain into the subconjunctival space, and the Xen gel implant (AqueSys/Allergan) drains into the subconjunctival space. All are pending FDA approval.

One surgeon’s experience

Carlos Buznego, MD, founding partner and an anterior segment surgeon at the Center for Excellence in Eye Care in Miami, said studies show that between 15% and 20% of cataract patients have coexisting open-angle glaucoma.

“So, the combination procedure of cataract plus glaucoma makes all the sense in the world,” he said.

Buznego said that nearly all of his older patients are highly receptive to having glaucoma treated with the iStent at the time of cataract surgery.

“They like the idea of killing two birds with one stone,” he said. “With just a few extra minutes added to the cataract portion, we can implant the iStent, which is the smallest stent implanted in humans.”

After the procedure, about 75% of patients no longer require glaucoma drops with no increased risk, according to Buznego. And even though there is only a modest reduction in IOP with the permanently implanted iStent, the alternative for many of these patients is long-term use of medications, Buznego said, noting that several large studies have found a high rate of noncompliance with eye drops.

The iStent is mostly indicated for patients with mild to moderate glaucoma.

“Therefore, it makes sense for ophthalmologists who are comfortable with anterior segment surgery to learn this procedure,” Buznego, who has implanted the iStent in more than 250 cases since 2008, said.

“Positioning for this procedure involves tilting the patient’s head away from the surgeon and tilting the microscope toward the surgeon to obtain a nice, flat view along the iris for the best visualization of the anterior chamber angle,” he said. “I call it the crop-duster view rather than the dive-bomber view.”

Furthermore, magnification levels for the iStent procedure can be dramatically larger than what the surgeon uses for traditional cataract surgery.

“I also recommend that surgeons avoid a big cup of Cuban coffee beforehand, as it is quite a delicate procedure,” Buznego said. “A tremor induced from caffeine or even from just a little bit of nervousness can sometimes make the procedure more difficult.”

The patient’s head should not be taped down because the patient will need to be tilted. “I find that it is very useful to have sterile handles on the microscope adjustment to make the alignment and positioning easier,” Buznego said.

Getting comfortable with MIGS

“Because the risks of the iStent are relatively low, I feel this is a great way for anterior segment surgeons to enter this arena,” OSN Cornea/External Disease Board Member Kenneth A. Beckman, MD, FACS, said. “If the procedure needs to be aborted due to blood in the angle and loss of view, then no harm has been done. Hyphemas are very rare; otherwise, it does not seem to cause any postop complications. When the device is implanted successfully, patients do very well and demonstrate a nice drop in IOP.”

Beckman said it takes about 10 cases for an anterior segment surgeon to become comfortable with the iStent.

“The key to getting through the learning curve is visualization. Without a good view of the angle, it is extremely difficult to place the device properly,” he said.

If the surgeon misses placement on the first attempt, it is not uncommon for bleeding to develop, which obscures the view. “The use of viscoelastic may push the blood out of the way to allow another attempt,” Beckman said. Other challenges are the unusual scope position, the patient head position and unfamiliar instruments.

Anterior segment surgeons who already manage glaucoma are likely already skilled with gonioscopy, Beckman said. However, surgeons need to learn how to perform gonioscopy under the operating microscope.

“This takes some getting used to and is not an intuitive or natural motion. With a little practice, though, this can be mastered,” he said.

Beckman recommended marking the microscope or at least keeping track of the number of knob rotations needed to position the scope at the desired angle, which can be time-consuming. “If the position is marked, or if the surgeon has another way to identify the proper position quickly, significant time can be saved when adjusting the scope,” he said.

To gain more practice in adapting gonioscopy under the scope, Beckman advocated that surgeons attempt gonioscopy on other patients who are not undergoing MIGS.

“It is definitely different from gonioscopy at the slit lamp,” he said.

Impact on glaucoma surgeons

Beckman said MIGS performed by anterior segment surgeons should not negatively affect glaucoma surgeons. “Often, glaucoma surgeons are not treating patients at this level,” he said.

According to Beckman, these patients, who often have controlled mild to moderate disease, might have undergone cataract surgery alone if MIGS was not available, so the glaucoma surgeon may have never seen these referrals. Such patients may have otherwise undergone selective laser trabeculoplasty by the cataract surgeon before cataract surgery or simply remained on their current medical regimen.

“[Glaucoma surgeons] are not typically affected by anterior segment surgeons performing MIGS,” OSN Glaucoma Section Editor Thomas W. Samuelson, MD, said. “In fact, many contemporary glaucoma surgeons are very busy anterior segment surgeons themselves.”

Samuelson said he believes that managing glaucoma on a regular basis prepares the surgeon “beautifully” for the common anterior segment pathologies of complex cataract, IOL complications, and coincident cataract and glaucoma. “Schlemm’s canal-based surgery and its intrinsic relationship to cataract surgery only propagate the union of glaucoma surgery and anterior segment surgery,” he said.

“If you want to better serve your patients with glaucoma, master phacoemulsification. Glaucoma and anterior segment surgery will become even more closely united as additional MIGS options become available,” he said.

One of the chief advantages of canal-based MIGS surgery “is that it is inherently safe,” Samuelson said. “All surgery has risk; however, compared to traditional glaucoma surgery, canal-based surgery is like operating with a safety net, as it eliminates one of the primary sources of perioperative risk: hypotony. Accordingly, experienced anterior segment surgeons are well-suited to perform MIGS, assuming they dedicate themselves to mastering the indications and techniques involved. But like any surgery, canal surgery requires preparation, repetition and dedication to the skill.”

“Glaucoma is such a widespread problem, affecting as much as 25% of patients who go through cataract surgery, that most glaucoma surgeons do not feel threatened by anterior segment surgeons performing MIGS,” OSN Cataract Surgery Section Editor John A. Hovanesian, MD, FACS, said. “Most of the glaucoma surgeons I know are happy that glaucoma is better controlled through more sources of effective therapy.”

Manageable learning curve

Angle-based MIGS has a definite but “very manageable” learning curve, according to Hovanesian, with most anterior segment surgeons feeling comfortable with the procedures after 10 to 20 cases.

Still, for the first few cases, Hovanesian said he believes it is worthwhile to have someone else in the room who is familiar with the steps and anatomy and can help provide guidance to surgeons who have never performed MIGS before.

The three biggest challenges with angle-based surgery are visualization, identification of anatomic landmarks in the angle and performing surgery guided by a mirrored gonioscopy lens, according to Hovanesian. For anterior segment surgeons who are new to gonioscopy, he recommended conducting the technique in the office on all patients in order to gain familiarity with the spectrum of appearance of tissues, “so in the OR you will not be caught off guard by unusual-looking cases.”

For instance, if a surgeon is targeting the pigmented Schlemm’s canal with an iStent and instead places it in the ciliary body band, which can look similar in some patients, the procedure is not going to work well, Hovanesian said. “Hence, you need to be familiar with the anatomy you are treating,” he said.

Hovanesian said gonioscopy is a valuable skill by itself and can be useful in any patient suspected of any form of glaucoma because it sometimes helps identify the type of glaucoma, such as pseudoexfoliation glaucoma or heavy pigmentation in pigment dispersion syndrome. Gonioscopy can also help detect peripheral anterior synechiae, “which may imply prior inflammation of intermittent episodes of angle-closure glaucoma,” he said. “Being familiar with gonioscopy allows us to be more comfortable in the OR doing angle-based MIGS.”

Other IOP-lowering procedures

Endoscopic cyclophotocoagulation (ECP) is another IOP-lowering procedure that is suitable for anterior segment surgeons.

“However, this procedure has not been widely embraced by the glaucoma community. It is being performed for the most part by cataract surgeons,” Buznego said.

After cataract surgery, usually within the same session, a laser with fiber optic capabilities allows the surgeon to visualize the ciliary processes, which are responsible for production of aqueous humor.

“By ablating this tissue with laser, there is decreased aqueous humor production and therefore corresponding reduction in intraocular pressure,” Buznego said.

Like the iStent, ECP has a fairly short learning curve, according to Luchs.

“The challenge with ECP is simply learning to operate via an endoscopic view,” he said. “You are watching a monitor, and your view comes through the laser endoscope itself.”

Despite the relatively short learning curve for ECP, there have been concerns, specifically in the glaucoma community, whether reducing aqueous humor production is the proper way to approach open-angle glaucoma. Furthermore, the ciliary processes are vascular, so a thermal burn of this tissue can incite significant ocular inflammation, which can be problematic, according to Buznego.

“Most modern cataract surgery patients expect rapid, pain-free recovery after their procedure,” he said.

Cost considerations

The cost of the ECP hardware may also be a factor impeding acceptance, along with hypotony occurring from overtreatment, according to Hovanesian.

“Advocates strongly favor using ECP, but they are relatively few in number so far,” he said.

Trabeculotomy, which historically has been used to treat infantile glaucoma but has gained resurgence with the advent of the Trabectome (NeoMedix), is another MIGS procedure that anterior segment surgeons can perform in conjunction with cataract surgery. The Trabectome is a device that uses electrocautery to incise the trabecular meshwork, thus allowing improved access of aqueous humor to the drainage area of Schlemm’s canal, Buznego said. However, like ECP, trabeculotomy has limited popularity, which may also be associated with the cost of acquiring the device and the expense of disposables, Buznego said.

The iStent has been well-received by Medicare and other insurance carriers, according to Buznego. As a primary procedure, stent implantation reimbursement is usually at 100%, while the cataract surgery is covered at 50%. But Luchs said that reimbursement varies state by state.

As the number of surgeons performing a specific operation increases, support for fair reimbursement also increases, Samuelson said.

For example, traditional glaucoma surgery, such as trabeculectomy and a tube shunt, is considerable work, requiring more intraoperative time and considerably more postoperative management than other anterior segment surgeries, according to Samuelson.

“Yet these procedures are relatively undervalued,” he said. “And there are simply not enough of us to effectively complain. However, as more surgeons perform specific procedures, their collective voice objecting to surgical fee reductions seems to resonate more, so perhaps it could help maintain a fair fee.”

Beckman said that as long as MIGS is safe, effective and manageable by the anterior segment surgeon, he expects the number of surgeons performing these cases to rise dramatically. He also believes that more glaucoma surgeons are likely to adopt MIGS, including those who currently perform cataract surgery. In addition, glaucoma specialists who perform combined glaucoma surgery with a cataract surgeon may find that MIGS can be scheduled instead of a more invasive procedure, yet still in combination with the referring cataract surgeon.

“The ability to do a minimally invasive procedure with great efficacy and low risk opens the door to much better management of these patients,” Beckman said. “Not only may it improve the control of the pressure, but it may also allow patients to discontinue drops that they would not have been able to do otherwise.”

Luchs said he expects the iStent will become a much more mainstream procedure over the next 12 to 18 months.

Future generations of these stents will become easier to implant, according to Hovanesian, who has used the iStent inject in clinical studies.

“The iStent inject is designed to greatly simplify insertion of the implant in Schlemm’s canal,” he said. “The surgeon simply places the stent tip on the appropriate location and then clicks a button, which injects the stent to an appropriate depth, thus removing some of the guesswork. But that said, the current generation iStent is not difficult to insert. It is sort of like starting an IV. You have to press with the right amount of pressure, and there is a little bit of finesse to it.”

According to Samuelson, “Glaucoma surgery and anterior segment surgery are becoming increasingly interwoven. Indeed, the fact that phacoemulsification favorably influences IOP is the very foundation for the MIGS revolution. As additional MIGS procedures become available, the relationship between glaucoma surgery and anterior segment surgery will become even more synergistic.”

Samuelson said improving the safety of incisional glaucoma surgery is a priority of MIGS.

“As the technology improves and becomes further refined, improvements in efficacy will follow as well,” he said. “The ultimate goal is to develop a portfolio of effective procedures that match surgical risk to the risk of functional impairment from glaucoma, thus allowing more individualized care.” – by Bob Kronemyer

• References:
• Ahmed II. Ophthalmology. 2015;doi:10.1016/j.ophtha.2015.06.022.
• Brandao LM, et al. J Ophthalmol. 2013;doi:10.1155/2013/705915.
• Caprioli J, et al. Ophthalmology. 2015;doi:10.1016/j.ophtha.2015.02.029.
• Khaimi MA. J Ophthalmol. 2015;doi:10.1155/2015/485065.
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• Seibold LK, et al. Middle East Afr J Ophthalmol. 2015;doi:10.4103/0974-9233.148344.
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• For more information:
• Kenneth A. Beckman, MD, FACS, can be reached at Comprehensive EyeCare of Central Ohio, 450 Alkyre Run Drive, Suite 100, Westerville, OH 43082; email: kenbeckman22@aol.com.
• Carlos Buznego, MD, can be reached at Center for Excellence in Eye Care, Baptist Medical Arts Building, 8940 North Kendall Dr., Suite 400-E, Miami, FL 33176; email: cbuznego19@gmail.com.
• John A. Hovanesian, MD, FACS, can be reached at Harvard Eye Associates, 24401 Calle De La Louisa, Suite 300, Laguna Hills, CA 92653; email: drhovanesian@harvardeye.com.
• Jodi I. Luchs, MD, FACS, can be reached at South Shore Eye Care, 2185 Wantagh Ave., Wantagh, NY 11793; email: jluchs@aol.com.
• Thomas W. Samuelson, MD, can be reached at Minnesota Eye Consultants, 701 E. 24th St., Suite 100, Minneapolis MN 55404; email: twsamuelson@mneye.com.

Disclosures: Beckman and Luchs report no relevant financial disclosures. Buznego reports he is a consultant to, investigator for and investor in Glaukos and a consultant and speaker for Allergan. Hovanesian reports he is a consultant to Glaukos and Ivantis and is a consultant to and equity holder of Sight Sciences. Samuelson reports he is a consultant to and/or investigator for Glaukos, Ivantis, AqueSys, Transcend Medical and InnFocus.

Has the time arrived for anterior segment surgeons to perform microinvasive glaucoma surgery at the time of cataract surgery?

The time has come

The time has clearly come for anterior segment surgeons to add MIGS to cataract surgery in order for supply to meet demand. The number of glaucoma patients has and will continue to increase for two major reasons. The first is that patients are now diagnosed earlier in life as technology to detect glaucoma improves and glaucoma awareness increases. The second is that life expectancy continues to expand over time. The combination of these two factors results in a relative increase in the number of glaucoma patients who need care. This growing demand, however, cannot be serviced with the current number of glaucoma specialists, as these numbers are not expected to change dramatically in the near future.

The overflow of glaucoma patients and their need for surgical intervention will naturally stream to the anterior segment surgeon. This will be the case because anterior segment surgeons provide a service that is both inevitable and critical to care of these patients — cataract surgery. The increase in life span has many consequences in medicine. In ophthalmology, it takes cataract surgery from a category of being performed in a faction of patients that may need it to a category that is considered an almost inevitable part of medical care in an average lifespan. If cataract surgery is now something that is expected to occur in a lifetime, then it raises the opportunity to take advantage of this surgery in providing better care. For those with glaucoma, this means the use of MIGS during cataract surgery.

MIGS with cataract surgery allows another opportunity to decrease IOP during a procedure that already is going to be performed without the violation of conjunctival tissue that may need to be used for trabeculectomy or tube shunt surgery. The addition of MIGS, therefore, can delay or possibly even prevent the need for riskier surgery in some patients. This leads to the most important goal of better quality of life. The real question becomes, which MIGS procedure in which anatomical target space (trabecular bypass, suprachoroidal or subconjunctival) and in what order should the procedures be performed?

Savak “Sev” Teymoorian, MD, MBA, is an OSN Glaucoma Board Member. Disclosure: Teymoorian reports he is a consultant for Allergan and Glaukos.

Cost is an issue

My current favorite microstent is CyPass (Transcend Medical), a polyimide device that provides a permanent conduit for outflow of aqueous humor from the anterior chamber to the suprachoroidal space, aided by the natural negative pressure in the eye. The microstent is inserted into the supraciliary space using an application device that allows a lateral, ab interno, clear corneal approach.

Because of the noninvasive, safe characteristics of the CyPass, patients with severe glaucoma progression with only minimal remaining visual field may benefit. If a trabeculectomy were performed at this advanced stage of glaucomatous disease, it is possible that the last of the patient’s remaining visual field would be lost.

The European population is aging. Cataract surgery presents a logical opportunity for adjunct surgical treatment for glaucoma. While cataract surgery may be combined with trabeculectomy, this is probably not the best option for patients with mild to moderate glaucoma. Given the logarithmically greater number of cataract surgery procedures relative to incisional standalone glaucoma surgical procedures performed annually, a safe, minimally invasive and effective glaucoma surgical adjunct to cataract surgery has the potential to become the most commonly performed glaucoma procedure worldwide.

Patients are generally more willing to undergo a glaucoma operation in combination with cataract surgery than as a standalone procedure. Glaucoma surgeries — even noninvasive ab interno procedures — carry the risk of inducing cataract development or progression. Combined procedures eliminate this risk. Also, the cost of a combined procedure is less than for separate glaucoma and cataract procedures.

One could, therefore, conclude that the time has arrived for anterior segment surgeons in Europe to perform microinvasive glaucoma surgery at the time of cataract surgery. However, the high cost of the microstents and the unwillingness of payers to cover the cost have so far applied a brake on this important surgical development.

Magda Rau, MD, is an OSN Europe Edition Associate Editor. Disclosure: Rau reports she is an advisor and consultant to Transcend Medical.