Eliminating, reducing complications “open the door to the EX-PRESS deviceâ€
The technique of trabeculectomy is pushing the field of glaucoma surgery forward in a way that has not been seen for many years. It is an exciting time. This discus- sion includes a review of some of the different glaucoma surgical options found to have moderate IOP reduction. A case report on a patient of mine demonstrates this efficacy.
Case report
This patient was first seen in 1993. At that time, he was 46 years old, with a history of glaucoma for 3 years and an IOP of 30 mm Hg. He was taking timolol and dipivefrin twice daily. At his initial examination, he was a moderate myope (–3.75 OU), with IOPs of 25 mm Hg and 22 mm Hg and extensive cupping, considering his age. The visual fields at that time were not bad, although there were some early defects. He was not very compliant, either with his follow-up visits or with medication. At his next examination in 2001, he said he had undergone a trabeculectomy in the left eye in 1995. He also had undergone bilateral PRK in 1997. At that time, he was taking latanoprost and timolol, although he admittedly noted his own poor compliance. He did not use drops in the left eye (the one that had undergone the trabeculectomy). On examina- tion, his IOP was 22 mm Hg in the right eye (the nonsurgical eye) and 4 mm Hg in the eye that had surgery. He had extensive cupping, with average-sized corneas.
The eye that had the trabeculectomy remained healthy and looked similar to the 1993 field examination. To me, this case illustrates clearly how trabeculectomy can make a difference in protecting the visual field and preserving vision. Those two goals—protecting the visual field and preserving vision—are why this surgery is performed.
Complications
Trabeculectomy may be one of the most commonly performed procedures, but it is not without its own set of potential complications, such as hypotony, flat ACs, and choroidals. The short-term problems include endophthalmitis, and the long-term problems include blebs and blebitis. The goal of glaucoma specialists is to eliminate or reduce those complications, and that’s what opens the door for surgical devices like the EX-PRESS Glaucoma Filtration Device (Alcon, Fort Worth, Texas).
There are alternative concepts being explored to modify the bleb, and additional new procedures that avoid bleb creation altogether are being developed. There is canal surgery, which includes tightening the trabecular meshwork. There are ways to direct flow to the suprachoroidal space, and there are meth- ods being investigated to reduce aqueous flow.
Some may question if one technique will dominate. In my opinion, that is likely not the case. Unlike another common condition—cataract—glaucoma is a complicated disease. Glaucoma, by diagnosis, encompasses a range of genetic conditions. Again, unlike a patient with a cataract where one procedure (phacoemulsification) can rectify the problem, with glaucoma patients there is not yet one single procedure that can resolve all the potential manifestations of the disease. Each procedure a surgeon performs should be customized to the patient.
Comparisons with trabeculectomy
As I noted earlier, trabeculectomy is a viable surgical option, but is not without its own set of complications; by modifying the procedure we hope to eliminate most of those complica- tions. One of the ways to modify a trabeculectomy is with the EX-PRESS device. In my hands, one of the major advantages to using the EX-PRESS device is the uniformity it creates in the major sclerosis sites.  With the EX-PRESS device procedure, there is minimal trauma, minimal inflammation, and minimal involvement of the iris. For surgeons who are not convinced trabeculectomy should be the surgical standard any longer, there are alternatives. For instance, three different tube shunts have been introduced. I prefer to use tube shunts more for advanced disease. With the three shunts— Ahmed (New World Medical, Rancho Cucamonga, Calif.), Baerveldt (Abbott Medical Op- tics, Santa Ana, Calif.), and Molteno (IOP Inc., Costa Mesa, Calif.)—the aqueous flow is distributed back to the equatorial reservoir 8-10 mm from the limbus. The aqueous flow creates a thick bleb wall. Shunts have some ad- vantages in complicated disease because they don’t cause scarring as easily.
In the landmark trabeculectomy versus tubes study, results found greater IOP lowering with trabeculectomy.1 That was an important study and seemed to change the scope of glaucoma surgery. However, anecdotal experience has found fewer long-term complications with tubes. There is also an issue with surgical ease—trabeculectomy is generally considered a fairly simple technique to master, while tube placement may have a longer learning curve and is generally more difficult.
Considerations
In glaucoma surgery, the surgeon needs to consider the efficacy of the procedure; the risk-complication profile; the technical ease of performing the procedure; how long the procedure takes to perform; what the cost is to the physician, the ASC, and the hospital; and finally, the reimbursement. In no-bleb glaucoma surgery, the key is to open the site of resistance in the angle at the site of the trabecular meshwork. This is an angled surgery procedure. The classic ap- proach has been trabeculectomy or goniotomy; the latter is usually limited to infants with congenital glaucoma. There are two new approaches—Trabectome (NeoMedix, Tustin, Calif.) and iStent (Glaukos, Laguna Hills, Calif.). The iStent has not yet been approved by the FDA. The Trabectome is a handpiece that has an infusion and a cutting mode on it. The bipolar electrode thermally ablates the strip of the trabecular meshwork and opens Schlemm’s canal to the anterior chamber. The footplate protects collector channels and controls incision depth. A side port paracentesis entry is made into the anterior chamber. Visceolastic is used to deepen the anterior chamber. This instrument is commonly used in combination with cataract sugary. The Trabectome probe is passed across the anterior chamber. It engages the trabecular meshwork and ablates at about the 4 o’clock position. In those with open- angle glaucoma, this ablation opens the side resistance of the eye; thousands of patients have been followed for up to 3 years. For patients with open-angle glaucoma, it plays an equally important role by potentially dropping average pressures to about 17-18 mm Hg. In early glaucoma, this may be a reasonable option for a select group of patients.
The iStent is one of the smallest medical devices implanted in the human body and is placed directly into the trabecular meshwork. The stent is attached to an inserter, which touches the trabecular meshwork and is then implanted into the canal space. The implant is injected, and the inserters are removed. Anecdotal experience has found that more than one iStent needs to be implanted to get the desired level of pressure reduction.
Canaloplasty is a third procedure and has been approved in the U.S. Canaloplasty is canal surgery with tightening of the trabecu- lar meshwork, in which a 300-micron flexible microcatheter with a lighted beacon tip is passed into the canal space. A superficial flap is created, and a deeper flap is created to pass the catheter into the canal space. The lighted beacon tip shows where it is in the canal space as it gently passes through. The catheter is passed 360 degrees and comes out the other end. A polypropylene suture is attached to the distal tip, and the catheter is removed. The canal has been dilated with the catheter and the viscoelastic. The canal is tightened with a polypropylene suture, and then the flap is closed. The advantage of this is there is no bleb. This is all done ab-interno. The surgeon is not depending on external drainage, and that makes it safer in the short and long term.
However, there is a learning curve with this technique. It takes some training to iden- tify the canal and feel comfortable working to pass this catheter through. For an experienced surgeon, this procedure will take about 30 minutes. For those who are just beginning to use it, it takes a bit longer.Results of canaloplasty show that it has great potential for certain types of patients. At 2 years, results average around 15.7 mm Hg in the phakic eye.2 This procedure is useful in patients where there might be a complication from trabeculectomy or because a trab failed in the patient’s other eye, there was significant conjunctival disease, or the patient is taking anticoagulants.
Conclusion
Cost has to be a consideration when surgeons think about implementing new procedures, but cost cannot be the driving factor - patient outcomes, reduced complications, and surgeon comfort must take precedence. There are numerous procedures we have available to improve outcomes from the standard trabeculec- tomy. In my opinion, the EX-PRESS device has the advantage of efficacy, reduced compli- cations, and improved predictability compared with trabeculectomy, and it is the most cost-effective option overall.
Editors’ note: This discussion includes off-label uses of glaucoma devices.
References
1. Gedde SJ, Schiffman JC, Feuer WJ, et al., for the Tube Versus Trabeculectomy Study Group. Three-year follow-up of the tube versus trabeculectomy study. Am J Ophthalmol. 2009;148(5):670-684; Epub Aug 11, 2009. 2. Lewis RA, van Wolff K, Tetz M, et al. Canaloplasty: Cir- cumferential viscodilation and tensioning of Schlemm’s canal using a flexible microcatheter for the treatment of open angle glaucoma in adults: two year interim clinical study results. J Cataract Refract Surg. 2009;35:814-824.Latest Articles
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