Focus on Glaucoma

Glaucoma patients have cause to cheer

As do surgeons: New treatment options are less invasive and less risky.

By Karen Blum, Contributing Editor

Davinder S. Grover, MD, MPH, loves GATT because it is noninvasive. Robert Chang, MD, appreciates that the MIGS’ upside is coupled with a low safety profile. Marlene R. Moster, MD, is grateful that combining ICE with the iStent gives aggressive glaucoma patients a better chance of lowering their IOP.

For many reasons, glaucoma surgeons are excited about the growth of new surgical options, tools and techniques for managing this disease.

“We’re moving away from the old-fashioned surgeries and looking toward quicker, more reliable and less risky surgery, so we can offer them to patients quicker in the timeline to prevent optic nerve degeneration and visual field progression,” says Dr. Moster, professor of ophthalmology at Thomas Jefferson University School of Medicine and an attending surgeon at Wills Eye Hospital in Philadelphia.

What follows is a discussion regarding the latest in glaucoma surgery technology and their benefits for ophthalmologists and their patients.

MICROINVASIVE GLAUCOMA SURGERIES

First-line procedures

Procedures to spare the patient’s conjunctiva, namely microinvasive glaucoma surgeries (MIGS), are the most interesting techniques for general ophthalmologists right now, says Dr. Chang, a glaucoma surgeon and assistant professor of ophthalmology at the Stanford Byers Eye Institute in Palo Alto, Calif., who uses a variety of techniques for his patients. “This is popular because it is easy to learn and is often combined with cataract surgery.”

With instruction, general ophthalmologists can use many of these techniques to manage patients with early glaucoma before trying more invasive treatments.

“The reason why surgeons offer minimally invasive surgery is that it has a low-risk safety profile and usually doesn’t preclude you from performing the more gold standard glaucoma procedures later,” Dr. Chang says. “MIGS may buy more time, and if it doesn’t lower the pressure enough, you can still do a trabeculectomy and tube shunt on pristine conjunctiva.”

MIGS options

The following have recently been added to the MIGS marketplace:

• The iStent Trabecular Micro-Bypass Stent (Glaukos). This tiny L-shaped titanium device, which is implanted in the eye during cataract surgery, helps to increase fluid flow. Approved by the FDA in 2012, iStent is intended for adults with mild to moderate open-angle glaucoma.

• Trabectome (NeoMedix). This surgical device ablates the trabecular meshwork to open access to Schlemm’s canal.

• Endoscopic cyclophotocoagulation (ECP). This laser treatment ablates the ciliary body to decrease the production of aqueous fluid.

GATT PROCEDURES

Departure from standard trabeculectomy

In 2011, surgeons at Glaucoma Associates of Texas, in Dallas, invented gonioscopy-assisted transluminal trabeculotomy (GATT), a conjunctival-sparing, sutureless ab interno approach for circumferential trabeculotomy for adult and pediatric open-angle glaucomas.

During the procedure, the surgeon creates a goniotomy, cannulates Schlemm’s canal and passes a suture or lighted microcatheter 360 degrees around the canal. The distal tip of the catheter or suture is then retrieved and externalized, creating the circumferential trabeculotomy (https://www.youtube.com/watch?v=A_UE5MverIA). This is a departure from the most common approach to trabeculotomy, ab externo, which requires an extensive conjunctival and scleral flap dissection that may diminish the success rate of a subsequent trabeculectomy, says Dr. Grover, an attending surgeon and clinician with Glaucoma Associates of Texas.

GATT study shows promise

Preliminary results from a recently published study, which included 85 patients ages 24 to 88, were at least equivalent to previously published results for ab externo trabeculotomy.¹

In 57 patients with primary open-angle glaucoma, intraocular pressure (IOP) decreased by an average of 7.7 mm Hg and patients had an average decrease in glaucoma medications of 0.9 at six months; by 12 months, these patients had an average IOP decrease of 11.1 mm Hg and needed an average of 1.1 fewer glaucoma medications. In 28 patients with secondary glaucoma, IOP decreased by 17.2 mm Hg at six months and 19.9 mm Hg at 12 months. They needed an average 2.2 fewer medications at six months and 1.9 fewer medications at 12 months. Also, early results after GATT in 10 patients with juvenile open-angle glaucoma or primary congenital glaucoma showed mean IOP decreased from 27.3 mm Hg to 14.8 mm Hg, and the mean number of required medications decreased from 2.6 to 0.86.

To date, Dr. Grover says he and his colleagues have performed GATT on more than 500 eyes, belonging to more than 300 people. They have reviewed data from patients treated over two years ago, and his group plans to publish the results, “which are just as good, if not better,” he says. “It’s very exciting that the results are standing the test of time.”

While some MIGS options stent open the canal or bypass the canal, getting a patient’s own drain to work is the ideal situation, Dr. Grover says. “The exciting thing about our procedure is that it does not involve any major incision on the eye. It is designed to open a patient’s own drain, and it’s a relatively safe, noninvasive procedure.”

Intraoperative images of key stages of GATT surgery.
COURTESY: DAVINDER S GROVER, MD, MPH

More surgeons have found success with GATT. For the past six months, Dr. Moster has treated about 30 patients and reports significant drops in IOP and reductions in needed glaucoma medications.

“This procedure preserves the conjunctiva and therefore avoids the complications associated with filtering blebs, while simultaneously preserving the 12 o’clock position for future glaucoma surgery,” she says. “That’s really why I was so interested in this — it gives us the opportunity to lower the IOP, utilizing very small incisions without the use of sutures, so vision can be quickly restored.”

Also, Dr. Moster says her group has successfully used a plasma blade to remove thick membranes in the anterior chamber. “This utilizes a unique energy source that allows for cutting of tissue without bleeding and without the destruction of surrounding tissue.” By removing membranes from over the pupil, vision can be restored.

ADDITIONAL GLAUCOMA DEVELOPMENTS

Combination procedures

Some glaucoma specialists have had success combining procedures. For example, the ICE procedure includes implanting the iStent, cataract extraction and ECP. Early results demonstrated a combined treatment reduced mean IOP from an average 19.l mm Hg to 15.5 mm Hg, with an average reduction of medications from 2.2 to 1.7.²

Dr. Moster has been using a combination approach for patients with more aggressive glaucoma, which she says provides “a double whammy.” The iStent may not lower pressure enough to guarantee pressures in the low teens, but the combination allows the iStent to maximize outflow while ECP decreases the aqueous production to reduce pressure. “It’s like maximizing the efficiency of a bathtub by improving the drainage while simultaneously turning down the faucet from the top,” Dr. Moster says. “These two different mechanisms of action are synergistic when combined with cataract surgery.”

On the horizon

Many more MIGS options are being tested in clinical trials, including the following:

• MIDI-Arrow Glaucoma Device (Innovia). A microtube drainage implant of unique material inserted into the anterior chamber of the eye to the subconjunctival space.

• XEN Gel Stent (AqueSys). A 6-mm stent the width of a human hair that creates a gentle outflow of aqueous from the anterior chamber to the subconjunctival space.

• Gold Shunt (SOLX). A biocompatible, pure gold implant that uses the eye’s natural pressure differential to reduce IOP.

• G3 Third Generation iStent (Glaukos). A newer iStent that can be inserted into the suprachoroidal space to potentially further reduce eye pressures.

• CyPass Micro-Stent (Transcend Medical). A device also inserted into the suprachoroidal space during cataract surgery to create a new pathway for fluid drainage.

Reaching the ultimate goal

With growing choices for glaucoma management, will surgeries like trabeculectomy remain the gold standard?

“I think there will be a lot of comparisons in terms of efficacy but even more importantly in terms of side effects,” says Richard A. Lewis, MD, a glaucoma specialist with Sacramento Eye Consultants in California. “That’s where I think the newer MIGS procedures are going to show tremendous promise, because the complications and side effects are significantly less.”

Dr. Chang is more hesitant, saying he’s waiting for five-year outcomes from the MIGS procedures and thinks there is room for both. As glaucoma is a chronic disease, ophthalmologists likely need multiple ways to lower eye pressure during a patient’s lifetime, he says.

“For this long-term, relatively slow progressive disease, we’re always fishing for something better to save or improve vision with fewer side effects,” he says. “I’m pretty sure it would spread like wildfire if there was one surgery that permanently restored aqueous drainage to the natural physiologic state.”

Dr. Grover says he sees this glaucoma technology fitting in this way: His first goal would be GATT or a similar procedure to open a patient’s natural drain. If that didn’t work, MIGS shunts or other devices that bypass a patient’s inherent drainage system could be a second option. If these procedures fail, he could turn to traditional surgical options.

“I think this is going to really diminish the number of patients who need these big traditional glaucoma surgeries,” Dr. Grover says. “That’s how it’s changed our practice over the past three years.”

Dr. Moster shares these sentiments, saying that MIGS procedures will become go-to procedures to lower pressure because of their decreased adverse risk profile.

“These new devices will maximize the suprachoroidal space and the area under the conjunctiva but with much less invasive procedures so the IOP can fall to the 14 to 15 mm Hg range on little or no medication.” OM

REFERENCES