Like a veteran heavyweight champion, trabeculectomy has defeated all challengers for the title as the procedure of choice for glaucoma patients who need very significant pressure lowering along with an appreciable reduction in their glaucoma medications. However, the procedure hasn’t rested on its laurels. Instead, surgeons have continued to perfect it by standardizing the steps, using different suture strategies and modifying their use of mitomycin-c. But new challengers wait in the wings, as companies have been developing other procedures and filtering devices, some penetrating, some minimally so.

In this article, we’ll look at recent advances in trabeculectomy, and review the latest procedures some surgeons are thinking about using alongside or in place of it.

Maximizing Trabeculectomy

Though the basic idea behind trabeculectomy has remained the same, surgeons have tweaked its various steps to optimize outcomes.

 • The resurgence of local anesthesia. Five years ago, Wills Eye surgeon Marlene Moster put forth her idea of topical “blitz” anesthesia in a journal article.1 She says she nicknamed it the blitz because the surgeon attacks pain from all angles—with topical gel, intracameral lidocaine and subconjunctival lidocaine—much like the way a quarterback is attacked by the blitz in football. Now, the concept is enjoying a renaissance of sorts, as surgeons try to follow cataract surgery’s lead and make trabeculectomy easier on the patient.

Dr. Moster has continued using the blitz for the past several years because “it lets you eliminate all the complications of doing a block,” she says. “You can also keep patients on their blood thinners, especially Coumadin, since many have atrial fibrillation or prosthetic valves that make it dangerous to stop the drug.” She only uses blocks on patients with whom she can’t communicate at all, such as those with severe mental retardation, in whom she’d consider general anesthesia. However, even with patients who don’t speak English, she’s used it successfully. “I ask the family to give me the phonetic spelling of such phrases as ‘look up,’ ‘look down’ and ‘don’t move’ in large print. I tape this sheet to the side of the microscope so it’s in plain view. With these statements in the patient’s language, I’ve been able to operate on Russians, Vietnamese—you name it.”

Dr. Moster says the topical blitz anesthesia consists of the following:

In the preop area, the patient gets 2% xylocaine jelly just before she is wheeled into the operating room, where she’s prepped with Betadine solution and draped. At the time of surgery, the first step is to make a paracentesis with a 30-degree Sharpoint blade and place 0.1 cc of 1% non-preserved lidocaine intracamerally. Then, after Dr. Moster makes a fornix-based conjunctival flap, she uses the same syringe used for the 1% lidocaine injection to irrigate under the conjunctiva and Tenon’s with additional lidocaine, and proceeds with the trabeculectomy. In the middle of the case, when it’s time to take out the block and do an iridectomy, she irrigates again with 1% lidocaine. Then, at the end of the procedure, with the same syringe on a 27-ga. cannula, she irrigates Tenon’s and the conjunctiva and closes the latter so it’s water-tight.

Dr. Moster says this protocol has served her and her patients well. “I promise them no pain and they have no pain during the surgery” she says. “The worst thing you can do is hurt somebody, because then everyone in the waiting room gets up and walks out!”

 • Perfecting fornix-based flaps. James Tsai, MD, chair of the department of ophthalmology and visual science at Yale says he’s adopted the fornix-based trabeculectomy with antimetabolite technique popularized by Moorfields surgeon Peng Khaw, MD. “Professor Khaw has advocated for fornix-based conjunctival flaps because he believes that the technique provides for a more diffuse, less ischemic-appearing filtration bleb with good IOP control and fewer risks of late onset bleb leaks and bleb-related infections—and I tend to agree,” says Dr. Tsai.

“With a limbus-based flap technique, scar tissue and vascularization can occur at the site of the posterior incision line and cause the formation of a small, localized bleb,” he says. “Even if you make the limbus-based incision 8 to 10 mm back, the scarring process can still shrink the dimensions of the filtration bleb, producing a small, ischemic bleb surrounded by a vascularized area of scar tissue. Nicknamed the ‘ring of steel,’ this scar tissue prevents the formation of a diffuse bleb, and this can result in recurrent bleb leaks. On the other hand, a well-healed, fornix-based conjunctival incision does not have the risk of scar tissue formation posteriorly and allows for the bleb to be more diffuse and have a wider surface area.”

Dr. Tsai also has adopted the technique of Utah’s Alan Crandall and Toronto’s Ike Ahmed that involves leaving a 1-mm conjunctival skirt at the limbus with a fornix-based incision, which facilitates a continuous running closure with a 9-0 vicryl suture. “This is most helpful since it eliminates the problems associated with closure of fornix-based conjunctival flaps with interrupted sutures and/or running corneal-conjunctival suturing at the limbus,” he avers.

• Minimizing mitomycin. In an effort to reduce the risk of potential problems from using adjunctive mitomycin, surgeons are reducing their concentration and/or duration of tissue exposure. “We started off with longer exposure times and higher concentrations, such as 0.5 mg/cc for five minutes or so,” says Peter Netland, MD, director of the glaucoma service at the University of Tennessee in Memphis. “Recently, the doses have been reduced. We’re typically using 0.25 mg/cc for one to two minutes, and we place the mitomycin sponges over a more diffuse area. By doing this, we feel we’ve reduced the number of problems we’ve seen, though I believe the procedure’s efficacy is still very similar to before.”

 • Fukasaku micro-trabeculectomy/sclerostomy. Yokohama, Japan’s, Hideharu Fukasaku, MD, designed a micro-punch that can be introduced through a 1-to-3 mm incision in a micro-trabeculectomy/sclerostomy. His video of the procedure was runner-up at the 2007 American Society of Cataract and Refractive Surgery’s annual film festival, in the category of new techniques.

He says the main advantage of the small-incision surgery is that it’s less traumatic than standard trabeculectomy, and therefore induces less scarring that might induce bleb failure.

He performs the procedure under sub-Tenon’s anesthesia that blocks the ciliary nerve. In the 3-mm incision procedure, he makes the conjunctiva and Tenon’s incision 8 mm posterior to the limbus. He then injects a small amount of 0.02% mitomycin, which he then washes out with an injection of BSS at the subconjunctival space.

Next, if necessary, he enlarges the sub-conjunctival space with a hockey knife. He then makes an oblique scleral tunnel with a 19-ga. V-lance knife (Alcon). He injects viscoelastic to maintain a deep anterior chamber. It’s at this point that he introduces the 20-ga. Fukasaku micro-punch into the tunnel and, with a pinching action, uses it to remove two to five bites of trabecular meshwork to open up the flow.

He uses a 20-ga. vitrector to make a peripheral iridectomy to avoid the internal sclerostomy incarcerating the iris, setting the device at 200 pulses/min. with a vacuum of 200 mmHg. He checks filtration through the tunnel and closes the peritomy. If flow is adequate, he closes Tenon’s and conjunctiva with a smaller number of sutures compared to traditional trabeculectomy (the 1-mm variant only needs one suture).

In a 12-month study of 29 micro-punch patients at Dr. Fukasaku’s practice, he says the average pressures are between 8 and 14 mmHg. He adds that around 10 to 20 percent of the patients have postop hypotony, with pressures around 10 mmHg; the pressure normalizes after two weeks. About 10 percent have bleeding from the peripheral iridectomy. However, he says he hasn’t experienced the scarring problems that can occur with a larger-incision trabeculectomy.

“The patients are still stable 18 months postoperatively,” says Dr. Fukasaku.

The New Kids on the Block

Amid the refinements of trabeculectomy, surgeons and companies have been hard at work developing new surgeries aimed at lowering pressure.

 • The ExPress implant. This device is aimed at being an adjunct to trabeculectomy that its maker, Optonol (Neve Ilan, Israel), hopes can standardize the procedure.

The ExPress is a 27-ga. tube with models that vary in length from 2.42 mm to just under 3 mm. The surgeon implants it under a partial thickness scleral flap, with one end in the anterior chamber and the other in the subconjunctival space. Aqueous is diverted to the latter, where it forms a bleb. There are three models that vary based on the size of the internal lumen (in microns) through which the aqueous flows: the R50; X50 and the X200. The R50 has a pointed tip while the latest version, the X50, has a blunt tip to obviate any possible problems of the tip striking the crystalline lens.

Steven Sarkisian, MD, of the Oklahoma University Health Science Center, has been working with the ExPress since 2003. He uses the X50 as his primary glaucoma procedure. “The main advantages, in my opinion, are first, the smaller hole for aqueous to flow through, which gives you less of a chance for hypotony and a more predictable flow rate,” he says. “Also, you’re only in the eye for about three seconds or so.” Dr. Sarkisian has no financial interest in the device or the company.

In a recent retrospective study in the Journal of Glaucoma, surgeons compared 50 eyes of 49 patients with the ExPress implant to 50 eyes of 47 patients treated with trabeculectomy. Though the mean intraocular pressure in the early postop period was significantly higher in the ExPress group, the IOP reduction was similar in both groups by three months. Early postop hypotony and choroidal effusion were significantly more frequent after trabeculectomy compared with ExPress implantation, however (p<0.001).2 Dr. Sarkisian estimates that the IOPs postop are usually between 10 and 13 mmHg with the X50, and between 7 and 9 mmHg with the larger X200.

 • Canaloplasty. This is a procedure that uses the Food and Drug Administration 510K-approved iTrack 250A microcatheter (iScience, Menlo Park, Calif.). Sacramento surgeon Richard Lewis is a clinical investigator for iScience, and describes how the procedure is performed: “We make a superficial scleral flap, then make a second, deeper flap to isolate Schlemm’s canal,” he explains. “We don’t enter the eye. We enter the canal, passing the iTrack around it 360 degrees. We attach a suture to the catheter, which we then withdraw, leaving the suture in the canal. During withdrawal, we use the microcatheter to inject viscoelastic to dilate the whole canal and collector system. We then draw the suture tight and leave it in to act like a stent to keep the canal open.” For the initial catheter threading maneuver, which can be challenging, a flashing beacon on the end of the catheter helps guide the surgeon through the canal. The other delicate part is determining how much tension to put on the suture.

Dr. Lewis recently presented data on 147 canaloplasty patients at the 2007 ASCRS meeting. Thirty-five patients reached the 12-month point, with an average IOP of 14.8 mmHg. Ninety-one percent needed glaucoma medications preop vs. 30 percent at a year. The most common complication is a hyphema which eventually resolves. A Descemet’s detachment is also possible.

 • Excimer laser trabeculostomy. This procedure, which employs a device that’s available in Europe but is not yet approved in the United States, uses a surgical approach similar to the Trabectome. The surgeon inserts the 500-µm ELT probe (EyeLight, Los Angeles, Calif.) through a corneal incision and its 200-µm laser fiber is brought into contact with the inferior/nasal trabecular meshwork on the side of the eye opposite the paracentesis. The surgeon visualizes the site through a goniolens or an endoscope. There, it delivers non-thermal 308 nm excimer laser energy that excises trabecular meshwork, juxtacanalicular trabecular meshwork and the inner wall of Schlemm’s canal without damaging the outer wall or the collector channels. In current protocols, the surgeon creates five to 10 openings with the device.

Beverly Hills, Calif., surgeon Michael Berlin, MD, who holds patents for the technology used in ELT, says the procedure enables pneumatic canaloplasty. “The non-thermal laser ablation turns tissue into gas, which pneumatically dilates Schlemm’s canal and collector channels, improving aqueous outflow,” he explains.

In a European clinical trial of ELT in 149 patients (104 of which were available for one-year follow-up), ELT lowered pressure from a preop average of 28 mmHg to 16 at 12 months postop. Dr. Berlin says that, once openings are created into Schlemm’s, as evidenced by blood reflux, they tend to stay open in the long term.

Dr. Berlin adds though, that before the procedure is brought to the United States, it will be improved “in order to incorporate the functionality current ELT surgeons desire in a complete solution.”

“Not all current applications are effective in creating inner-wall openings,” he says. “This is because Schlemm’s canal is not always adequately targeted and the system parameters at this stage are limited.” The improvements  will take the form of a computer-controlled procedure, called Enhanced ELT, in which the system and laser respond to the surgeon as the surgeon moves the probe. The Enhanced ELT system is currently in development.

 • The Trabectome. This is a handpiece made by NeoMedix, of Tustin, Calif. It’s approved in the United States.

In practice the Trabectome is inserted into the eye through a temporal clear-corneal incision. The surgeon then uses a modified Swan-Jacobson lens to view the angle, holding the mirror with one hand while using the Trabectome with the other. The probe uses bipolar electrocautery to remove some of the trabecular meshwork to improve aqueous outflow, while not harming the outer wall of Schlemm’s canal thanks to a protective footplate on the device.

Quang Nguyen, MD, of the Scripps Clinic in San Diego, says he likes the procedure for a couple of reasons. “It makes sense from a physiologic standpoint,” he says. “You’re ablating the trabecular meshwork while leaving the outer wall of Schlemm’s canal and the collector channels intact for drainage. Second, you don’t use conjunctival tissue to perform it, it’s an ab interno approach, so you’re not disrupting conjunctiva that you may need if you have to do a trabeculectomy later.” For the best effect, Dr. Nguyen recommends ablating at least 100 degrees of the trabecular meshwork.

“I think a patient with ocular hypertension or early glaucoma, or one with a history of non-compliance, may benefit from this because it will get him off of his medications,” says Dr. Nguyen. “In my experience, and according to what’s been reported in pooled data, the best effect you’ll get is pressure control in the mid-teens, because it follows the physiology of the drainage system.” Dr. Nguyen says the failure rate in his study of 15 patients is about 20 percent, which is just a little more than the 16 percent rate reported in a large published study.3 Dr. Nguyen says a small pressure spike is possible in no more than 5 percent of patients, and that reflux bleeding from episcleral venous pressure is common, but clears in a day.

• Solx gold micro-shunt. This is a 24-karat flat plate that’s 5.2 mm long, 3.2 mm wide and comes in sizes that are 44 and 68 µm thick. The plate has microchannels designed to let aqueous flow from the anterior chamber to the suprachoroidal space. Robert Noecker, MD, director of the glaucoma service at the University of Pittsburgh School of Medicine, is taking part in the Phase III United States trial of the device. “One size is used for patients with pressures in the low 20s and below, and the larger size is for pressures near 30 mmHg,” he says.

Upon implantation, the tail of the device goes into the anterior chamber, through the angle, and the other end of it is back in the suprachoroidal space, approximately over the pars plana. “It becomes a track through which the aqueous can flow,” says Dr. Noecker.

For future iterations, Dr. Noecker says the plan is to use a laser, also made by Solx, to open up one or more of the channels in the device to increase flow. That step isn’t performed in the U.S. clinical trial, however.

“With the smaller shunt we’re typically seeing pressures brought down from the low 20s to the mid to upper teens,” says Dr. Noecker. “With the larger shunt, we’re seeing pressures brought down from upper 20s or 30 to the mid to upper teens.”

The most common complication so far has been transient hyphema, which has been reduced somewhat as surgeons become more skilled. “Also, if you get a lot of blood or fibrin, you can block these channels, which are only about 40 µm or so. Second, since the device is made of gold, which is soft, if you mishandle the device you can crush the microchannels.”

Though the alternatives to trabeculectomy are proliferating, it’s not clear yet whether any will be able to topple the champion from its perch in terms of per-procedure cost (a trabeculectomy doesn’t require the purchase of a device), long-term results or the ability to get patients off of medications.

“I think these procedures are promising,” says Dr. Netland. “But, it’s hard to determine where these things will fit when compared to trabeculectomy.”  

1. Kansal S, Moster MR, Gomes MC, et al. Patient comfort with combined anterior sub-Tenon’s, topical, and intracameral anesthesia versus retrobulbar anesthesia in trabeculectomy, phacotrabeculectomy, and aqueous shunt surgery. Ophthalmic Surg Lasers 2002;33:6:456-62.

2. Maris PJ Jr, Ishida K, Netland PA. Comparison of trabeculectomy with Ex-PRESS miniature glaucoma device implanted under scleral flap. J Glaucoma 2007;16:1:14-9.

3. Minckler D, Baerveldt G, Alfaro Ramirez M, et al. Clinical results with the trabectome. Trans Am Ophthalmol Soc 2006;104:40-50.