March 2017

 

INTERNATIONAL

 

Presentation spotlight

Trabeculectomy: Still relevant in the wake of MIGS


by Stefanie Petrou Binder, MD, EyeWorld Contributing Writer

   
Uriant bleb
Uriant bleb covering the cornea

Small avascular blebSmall avascular bleb after mitomycin C-augmented trabeculectomy

Lebitis
Lebitis with large avascular area after mitomycin C-augmented trabeculectomy

Optimal bleb formation
Optimal bleb formation after mitomycin C-augmented trabeculectomy
Source (all): Anselm Jünemann, MD

While recognizing its advantages, a German specialist explains why MIGS devices cannot entirely replace trabeculectomy

Change is not always easy to embrace, particularly when your methods are tried and true, reliable and effective. But, the most stubborn nonbelievers cannot deny the stunning IOP relief achieved by microinvasive glaucoma surgery (MIGS). Anselm Jünemann, MD, professor of ophthalmology, Rostock University Eye Clinic, Rostock, Germany, discussed his 180-degree turnaround regarding the role of MIGS devices in modern glaucoma surgery, and why, despite the evidence, he cannot turn his back on trabeculectomy.
“We have an abundance of new operative techniques in glaucoma surgery. The question is whether new techniques replace old ones or whether it is prudent to keep the old ones alongside the new, using them as we see fit, according to the level of success or failure we achieve with selected techniques,” Dr. Jünemann said during a presentation he gave on the topic at the 114th Congress of the German Ophthalmological Society, which was held September 29 through October 2, 2016.

The case for MIGS

According to Dr. Jünemann, the facts speak loudest. In a prospective open-label randomized study that used the iStent (Glaukos, San Clemente, California) in 62 eyes of 43 patients with primary open-angle glaucoma (POAG), pseudoexfoliation glaucoma, ocular hypertension, or secondary/post-traumatic glaucoma, the 3-year outcomes showed a sustained reduction in IOP, from mean preoperative 24.1 mm Hg, to a mean of 14.9 mm Hg at 36 months, and an excellent safety profile.1 The mean pressure reduction of 8.5 mm Hg outdid the mean reduction of 4.1 mm Hg observed after a 3-year follow-up period in the Ocular Hypertension Treatment Study (OHTS), which examined the effect of topical ocular hypotensive medication in POAG patients, who had a mean preoperative IOP of 23.9 mm Hg.2
Another prospective pilot study involved implantation of two trabecular micro-bypass stents in 39 open-angle glaucoma patients, achieving a significant and sustained reduction in IOP and medication over 18 months of follow up.3 The mean unmedicated IOP decreased from 25.3 mm Hg preoperatively to 17.1 mm Hg at 13 months. In a published review on the iStent, the authors show the safety and efficacy of the iStent system based on the outcomes of randomized controlled clinical trials, revealing IOP reductions of 8–27% and medication reductions from 80–100%.4
Dr. Jünemann elucidated that other MIGS devices like the iStent, Hydrus (Ivantis Inc., Irvine, California), Cypass (Alcon, Fort Worth, Texas), and AqueSys XEN gel stent (Allergan, Dublin, Ireland) showed promise but were not as well-documented through clinical trials. One investigation in open-angle glaucoma patients presenting with IOP values between 22–38 mm Hg revealed a mean postoperative IOP of 15 mm Hg without medications using the iStent,5 while the Hydrus achieved at least 20% IOP reduction in 80% of the 100 study eyes with open-angle glaucoma at 24 months after combined cataract plus Hydrus implantation surgery.6 Initial clinical experience with the Cypass micro-stent showed a mean reduction in IOP of 9.6 mm Hg and reduced medications in a study that combined the Cypass with cataract surgery in 167 eyes.7 Finally, cataract surgery combined with the implantation of the XEN gel stent resulted in a postoperative reduction in IOP of below 18 mm Hg in 85% of 37 eyes with open-angle glaucoma.8
“These MIGS devices each take advantage of different drainage options within the aqueous drainage meshwork. The iStent is a trabecular stent that reduces transtrabecular resistance. The Hydrus is a Schlemm’s canal microstent, while the Cypass uses the suprachoroidal drainage system to shunt aqueous, increasing uveoscleral outflow. The XEN gel stent, however, comes close to traditional filtration surgery by shunting aqueous into the subconjunctival space, but is performed ab interno, freeing up all points of resistance. So the question is: is this good enough? The results are compelling. However, I believe that even though making use of transtrabecular, suprachoroidal, and filtrating mechanisms to reduce IOP lets us treat every type of patient, we still need trabeculectomy,” Dr. Jünemann said.

Case for trabeculectomy

For Dr. Jünemann, the exceptional results achieved through MIGS to lower raised IOP in open-angle glaucoma patients do not preclude the further implementation of trabeculectomy. In fact, there are scenarios in which he would choose trabeculectomy as the best choice for the patient. “The idea of completely switching from a trusted ab externo procedure to MIGS is a true dilemma, because for me trabeculectomy has always been part of my armamentarium for glaucoma surgery. I may be accepting of new ideas, but I still hold on to this valued procedure. MIGS is still very new.”
The American Glaucoma Society and U.S. Food and Drug Administration convened in 2014 to agree upon a unified definition of MIGS. It was characterized as an ab interno procedure, with minimal tissue interaction (wound healing), effective IOP reduction, and high safety. The adequate IOP reduction for MIGS was set at a middle reduction of 20% or more of the midday IOP without medications; and/or a reduction of at least 3 mm Hg.
“There is a therapeutic dilemma, however, in this definition, regarding the target pressure concept because patients who have raised IOP of short duration, or slowly rising early IOP need a higher target IOP than patients who have advanced, long-standing, fast-rising IOP, who require a lower target IOP. Many factors play into deciding the target pressure for a patient,” he explained.
Dr. Jünemann believes that patients with advanced long-standing or quickly-rising IOP are still best served by trabeculectomy. Apart from the Xen gel stent, which has been shown to be effective in increasing filtration of aqueous, trabeculectomy is likely to still be the surgeon’s best choice.
“An experienced surgeon can create a good filtration bleb and tenon suture, making this an excellent, effective pressure-relieving surgery. The XEN bleb is much like the trabeculectomy bleb. However, the advantages of trabeculectomy over the XEN MIGS stent is that it is performed reliably from the outside of the eye allowing us to reliably surgically define a drainage shaft. By continuing to perform trabeculectomy, our young surgeons stay in practice, sew and suture, and continue to learn more about the eye tissues, through surgery. After all, experience is not inherited,” he said.

References

1. Neuhann TH. Trabecular micro-bypass stent implantation during small incision cataract surgery for open-angle glaucoma or ocular hypertension: Long-term results. J Cataract Refract Surg. 2015;41:2664–71.
2. Kass MA, et al. The Ocular Hypertension Treatment Study: A randomized trial determines that topical ocular hypotensive medication delays or prevents the onset of primary-open-angle glaucoma. Arch Ophthalmol. 2002;120(6):701–13.
3. Ahmed IK, et al. Prospective evaluation of microinvasive glaucoma surgery with trabecular microbypass stents and prostaglandin in open-angle glaucoma. J Cataract Refract Surg. 2014;40:1295–1300.
4. Wellik SR, Dale EA. A review of the iStent trabecular micro-bypass stent: Safety and efficacy. Clin Ophthalmol. 2015;9:677–684.
5. Voskanyan L, et al. Prospective, unmasked evaluation of the iStent Inject System for open-angle glaucoma: Synergy Trial. Adv Ther. 2014;31:189–201.
6. Pfeiffer N, et al. A randomized trial of a Schlemm’s canal microstent with phacoemulsification for reducing intraocular pressure in open-angle glaucoma. Ophthalmology. 2015;122:1283–93.
7. Hoeh H, et al. Initial clinical experience with the Cypass Micro-Stent: Safety and surgical outcomes of a novel supraciliary microstent. J Glaucoma. 2016;25:106–12.
8. Sheybani A, et al. Phacoemulsification combined with a new ab interno gel stent to treat open-angle glaucoma: Pilot study. J Cataract Refract Surg. 2015;41:1905–09.

Editors’ note: Dr. Jünemann has financial interests with Alcon, Allergan, and Glaukos.

Contact information

Jünemann: anselm.juenemann@med.uni-rostock.de

Trabeculectomy: Still relevant in the wake of MIGS Trabeculectomy: Still relevant in the wake of MIGS
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