Studies have found that the EX-PRESS™ Glaucoma Filtration Device may reduce some complications without compromising the efficacy of glaucoma filtering surgery, subtly changing the risk/benefit ratio and making filtration surgery a bit more attractive for some patients facing trabeculectomy.
Although decades old, trabeculectomy is arguably the most effective means at our disposal for lowering intraocular pressure (IOP). Over the years, trabeculectomy has been incrementally improved by the addition of antifibrotics and the adoption of tight flap closure with planned laser suture lysis. Today, there exists a substantial pool of surgeons who have become highly proficient at the procedure.
While trabeculectomy continues to have great value, it is not without drawbacks: It requires intensive follow-up and is associated with a high level of intraoperative and postoperative complications compared with modern cataract surgery. In addition, individual variations in wound healing make it difficult to predict which patients will be successful with trabeculectomy—some patients simply cannot obtain sufficient IOP reduction despite aggressive postoperative care.
Compared to many other ocular surgeries, failure rates with trabeculectomy are high: reports from the Fluorouracil Filtering Surgery Study found a failure rate of 27% at 1 year and 51% at 5 years.1,2 Similar rates were reported in the Singapore 5-fluorouracil study.3 Even though trabeculectomy has stood the test of time, there is clearly room for improvement in both rates of success and in reduction of complications.
Minimally Invasive Glaucoma Surgeries
A number of less invasive glaucoma procedures have arisen in recent years (with more in development), including canaloplasty and several small drainage implants that can be placed either during cataract surgery or in a dedicated procedure. These “minimally invasive glaucoma surgeries” (MIGS) have the advantage of fewer complications and, in some cases, a simpler surgical procedure. But none of them can reliably produce IOP lowering like trabeculectomy.
The Alcon EX-PRESS™ Glaucoma Filtration Device provides a modification to the strategy of aqueous diversion to the subconjunctival space. Refined over a number of years, EX-PRESS is not a MIGS device; instead, the EX-PRESS is a short tube with a 50-micron lumen and a flat external plate that is implanted under a scleral flap (Figure 1). The implantation procedure is much like trabeculectomy—and is similar to trabeculectomy in surgical maneuvers—but with some important differences.
The internal lumen of the EX-PRESS device limits fluid passage, providing a more predictable rate of outflow. Among other things, this reduces the loss of anterior chamber depth often seen during trabeculectomy and may reduce the risk of early postoperative hypotony according to some reports. Nonetheless, the IOP lowering that can be achieved with EX-PRESS is similar to that of trabeculectomy and meticulous technique is required. In addition, some have reported lower rates of intra- and postoperative complications with EX-PRESS.
An early retrospective case-control study comparing EX-PRESS with trabeculectomy found that the EX-PRESS group had significantly less postoperative hypotony and choroidal effusion than the trabeculectomy group.4 Although the EX-PRESS group had a higher mean IOP in the early postoperative period—possibly due to hypotony in the trabeculectomy group—there was no significant IOP difference after 3 months. From 3 to 15 months (the end of the review period), success rates were identical. In this study, EX-PRESS provided similar IOP reduction with fewer complications than trabeculectomy.
In a prospective randomized study comparing EX-PRESS with trabeculectomy, deJong and coworkers studied 80 open-angle glaucoma eyes in which IOP could not be sufficiently controlled with medication.5 At 1 year after surgery, IOP control status was identical between the EX-PRESS group and the trabeculectomy group. With success defined as an IOP between 4 mmHg and 18 mmHg, the success rate in the EX-PRESS group was 85% vs 60% in the trabeculectomy group. Postoperative interventions and complications were similar.
A subsequent paper reporting 5 years of follow-up found mean IOP control was almost exactly the same in both groups, while the EX-PRESS group was more successful in achieving target IOP. The time to failure was also significantly longer in the EX-PRESS group.6
Finally, a recently published prospective contralateral eye study by Dahan and coworkers reported after 30-month follow-up that IOP in the trabeculectomy group decreased from 31.0 mmHg to 16.2 mmHg while that in the EX-PRESS group dropped from from 28.1 mmHg to 15.7 mmHg; the trabeculectomy group, however, required more medication to achieve this IOP reduction, and the survival rate (defined as an IOP between 5 mmHg and 18 mmHg) was significantly greater in the EX-PRESS group.7
Failure rates in trabeculectomy are high, and the surgical procedure is challenging. Trabeculectomy creates a fistula in the sclera that permits aqueous humor to flow into the subconjunctival space, creating a bleb. In some patients, healing effects can slowly shut down the flow of aqueous, and over time the effectiveness of a trabeculectomy bleb can decline or be lost. Although the procedure adopts a similar anatomic strategy, some reports suggest that, with EX-PRESS, there may be fewer complications and better survival of IOP control. It must be noted that EX-PRESS can be associated with all the complications seen with trabeculectomy, including failure.
A study by Good and Kahook compared visual recovery after trabeculectomy to recovery after EX-PRESS implantation. They found that visual acuity recovered to the preoperative level 1 week after surgery in the EX-PRESS eyes, while in the trabeculectomy group this recovery was not observed until the 1 month visit.8 Unlike a change in IOP, faster return of vision is something patients can recognize and appreciate. Good and Kahook also found fewer cases of early postoperative hypotony and hyphema in the EX-PRESS group, which also required fewer postoperative visits.
EX-PRESS surgery itself offers the opportunity for greater intraoperative control than trabeculectomy. Trabeculectomy creates an ostium in the eye wall, and even with pre-placed sutures there is inevitable shallowing of the anterior chamber, forward movement of the lens, and a point at which IOP is essentially zero prior to closure of the flap—always a tense moment for the surgeon. With the EX-PRESS, instead of an ostium in the wall, there is a small (25 g to 27 g) needle entry, so the anterior chamber can remain formed and under the control of the surgeon.
Another potential advantage of the EX-PRESS procedure is that it does not require an iridectomy. This is a clear advantage for patients with vitreous behind the pupil from complicated cataract surgery, and for those on anticoagulants. Additionally, for patients on anticoagulants, EX-PRESS is much less invasive—the small needle entry into the anterior chamber creates much less bleeding.
While EX-PRESS does not replace trabeculectomy, many trabeculectomy surgeons will find it an excellent addition to their armamentarium. For patients on anticoagulants or for whom it is desirable to avoid iridectomy, EX-PRESS may be the obvious preferred procedure. Conversely, in eyes with angle closure glaucoma or where there are space constraints for the EX-PRESS, trabeculectomy may be the better choice.
EX-PRESS in Context of Glaucoma Surgeries
The EX-PRESS procedure does not qualify in my view as minimally invasive, but it is incrementally less invasive than trabeculectomy. It is not for every surgeon and it is not for every eye. For surgeons who prefer not to do trabeculectomy, EX-PRESS is not a reason to start. But for surgeons who are comfortable performing trabeculectomy, EX-PRESS is a useful option. There is data to support the suggestion that EX-PRESS may reduce some complications, increase the survival of IOP control, and make the surgery itself a little more controlled.
In terms of IOP lowering, the EX-PRESS procedure is comparable to trabeculectomy. It can be considered for patients in whom trabeculectomy is being considered. There are reports of complications with the EX-PRESS procedure, but proper technique can minimize those. EX-PRESS is not indicated in eyes for which trabeculectomy would be contraindicated; and like any device, EX-PRESS can be mishandled or improperly implanted, but the chance of this diminishes rapidly with training and experience. Although it is not universally the case, some surgeons report that the postoperative course is smoother and vision returns earlier in EX-PRESS patients compared to trabeculectomy patients. For these patients, having fewer postoperative visits means a lesser burden on themselves and their families.
Like any advance in surgical technology, EX-PRESS has the potential to shift the risk/benefit ratio with thoughtful patient selection and meticulous technique. When we consider any change in our glaucoma surgical procedures, the potential for an improved safety profile or a reduced burden for the patient should be a factor in our recommendations and increase our comfort level in making those recommendations.
THE BOTTOM LINE
Studies have reported that the EX-PRESS Glaucoma Filtration Device can enhance glaucoma surgery by reducing complications (particularly hypotony following surgery), hasten visual recovery in some patients, lengthen the survival of IOP control, and allow the surgeon to maintain better control of the eye during the procedure. IOP lowering with the EX-PRESS is comparable to trabeculectomy; and while the EX-PRESS is neither minimally invasive nor a replacement for trabeculectomy, it offers an attractive option in many patients for whom trabeculectomy is being considered.
Robert D. Fechtner, MD, is a professor at the Institute of Ophthalmology and Visual Science, UMDNJ-New Jersey Medical School and director of the Glaucoma Division, UMDNJ-New Jersey Medical School, Newark, NJ. He is a consultant to Alcon. Medical writer Tony Hampton assisted in the preparation of this manuscript.
1. Fluorouracil Filtering Surgery Study one-year follow-up. The Fluorouracil Filtering Surgery Study Group. Am J Ophthalmol. 1989;108(6):625-35.
2. Five-year follow-up of the Fluorouracil Filtering Surgery Study. The Fluorouracil Filtering Surgery Group. Am J Ophthalmol. 1996;121(4):349-66.
3. Wong TT, Khaw PT, Aung T, et al. The Singapore 5-Fluorouracil trabeculectomy study: effects on intraocular pressure control and disease progression at 3 years. Ophthalmology. 2009 Feb;116(2):175-84.
4. Maris PJ Jr, Ishida K, Netland PA. Comparison of trabeculectomy with Ex-PRESS miniature glaucoma device implanted under scleral flap. J Glaucoma. 2007 Jan;16(1):14-9.
5. de Jong LA.The Ex-PRESS glaucoma shunt versus trabeculectomy in open-angle glaucoma: prospective randomized study. Adv Ther. 2009;26(3):336-45.
6. de Jong L, Lafuma A, Aguadé AS, Berdeaux G. Five-year extension of a clinical trial comparing the EX-PRESS glaucoma filtration device and trabeculectomy in primary open-angle glaucoma. Clin Ophthalmol. 2011;5:527-33.
7. Dahan E, Ben Simon GJ, Lafuma A. Comparison of trabeculectomy and Ex-PRESS implantation in fellow eyes of the same patient: a prospective, randomised study. Eye. 2012 May;26:703-10.
8. Good TJ, Kahook MY. Assessment of bleb morphologic features and postoperative outcomes after Ex-PRESS drainage device implantation versus trabeculectomy. Am J Ophthalmol. 2011 Mar;151(3):507-13.