When we evaluate glaucoma patients' candidacy for surgery, it is useful to classify them according to their disease, underlying medical conditions, and their estimated life expectancy. This information helps us decide whether to perform surgery, what type of surgery to perform, and when.
Trabeculectomy has traditionally been glaucoma surgeons' surgical standard; it is a continuously evolving procedure that we each execute slightly differently. During my career, I have seen several important advancements in trabeculectomy surgery, including fornix-based limbal conjunctiva incisions, standard wound-management techniques, and releasable or laserable flap-suture techniques. These innovations have helped me immeasurably to improve outcomes and avoid complications.
When considering using the EX-PRESS Glaucoma Filtration Device (Alcon Laboratories, Inc., Fort Worth, Texas), I think it is essential that we understand both the “how” of the surgical technique and the “whom” of patient selection.
THE EX-PRESS DEVICE: WHAT IS IT?
The EX-PRESS Glaucoma Filtration Device is a small, stainless steel implant less than 3 mm in size (Figure 1). It has a channel that diverts aqueous from the anterior chamber under a scleral flap. The version of the EX-PRESS device I currently use (the P-50 model) has one port at the tip that faces into the eye, and another port that faces anteriorly toward the cornea. The anterior port helps avoid occlusion of the tip; even if some of the iris should touch the tip, there is a slot in the footplate that directs aqueous posteriorly and helps the surgeon correctly orient the device.
ADVANTAGES AND DISADVANTAGES
Why not just continue performing trabeculectomy in every glaucomatous patient? Many glaucoma surgeons have found several aspects of trabeculectomy surgery to be problematic. The EX-PRESS Glaucoma Filtration Device is useful in making a portion of the surgery more predictable and avoiding certain complications. The device provides an opening of approximately 50 μm to somewhat regulate outflow. Additionally, the EX-PRESS device has demonstrated IOP-lowering efficiency similar to trabeculectomy, and it can reduce certain intraoperative complications and offer alternatives for postoperative care.
No single type of glaucoma surgery is right for all patients, and the EX-PRESS device may not be suitable for all eyes that need surgical reduction of IOP. The cost associated with this procedure has also been cited as a drawback compared with trabeculectomy.
IOP CONTROL: A RETROSPECTIVE STUDY
An early indicator of the usefulness of the EX-PRESS Glaucoma Filtration Device was a retrospective study of IOP control that compared the device with trabeculectomy. This report by Maris et al1 showed that by 6 months, the pressure control was identical between trabeculectomy patients and EX-PRESS device patients. There was a higher mean IOP in the EX-PRESS device group in the early postoperative period. The success rate between the two groups was virtually identical, however.
PREOPERATIVE CONSIDERATIONS
How can we successfully use the EX-PRESS Glaucoma Filtration Device? My first guideline for implanting this device is to choose the right patients. My rule of thumb is that individuals who are poor candidates for trabeculectomy should not be considered for implantation with the EX-PRESS device. For me, these include patients with uveitis, neovascular glaucoma, or severe dry eye.
Preoperative gonioscopy is essential to effectively using the EX-PRESS device; you must know what is going on in the superior angle before you an attempt an implantation. Narrow angles can make placement of the EX-PRESS device difficult.
CONJUNCTIVAL INCISION, ANTIFIBROSIS AGENTS
When making the conjunctival incision, I use the same approach as for trabeculectomy, provided that the incision is large enough to accommodate the delivery of standard wound management techniques and suturing of the flap. A fornix-based limbal incision maximizes exposure. I use my same wound-management techniques as with trabeculectomy.
THE SCLERAL FLAP
It is very important to create a properly sized scleral flap for the EX-PRESS device procedure. One common technical error is to make the flap too small and leave part of the implant exposed. A depth of 3 x 3 mm is sufficient to provide good coverage. Leave the sclera thick enough to cover the device on top and to support it from underneath; I consider 300- to 400-μm flap thickness to be a good starting point in a normal eye. I encourage my colleagues to be cautious implanting the EX-PRESS device in eyes with thin sclera, such as high myopes, because they may not have enough scleral thickness to adequately support and cover the device.
ROLE OF THE PARACENTESIS
The paracentesis plays an important role in terms of deepening the chamber prior to inserting the EX-PRESS device. Making the paracentesis can cause some aqueous to escape and induce the iris to move forward. Our goal is to recreate that space to allow for easy insertion of the device. I suggest creating a paracentesis similar to that used in trabeculectomy; it may be helpful to use an ophthalmic viscoelastic device for the first several cases.
ENTRY UNDER THE SCLERAL FLAP
Inserting the EX-PRESS Glaucoma Filtration Device under the scleral flap is an important aspect of performing the EX-PRESS device procedure. In my opinion, a 25-gauge needle is more than sufficiently large for this purpose. A 27-gauge needle is too small, unless you enlarge the opening. Some surgeons who desire a tighter fit may use a smaller needle, but for early cases, I think a 25-gauge needle is suitable. Because the plate has an anterior portion, it is important to leave space between the entry site and the anterior hinge of the flap—I prefer 1 mm from the hinge.
INSERTION AND FLAP CLOSURE
The EX-PRESS device inserter (Figure 2) is quite easy to use. It features a wire and an injector trigger button. Pressing on the release point causes the wire to withdraw, leaving the EX-PRESS device behind (Figures 3 and 4). Prior to entry, I keep the inserter in my hand, with my finger positioned over the injector trigger to allow for easy release.
Flap closure with the EX-PRESS device is slightly different than with trabeculectomy, because the former greatly slows the flow of fluid, and if the surgeon does not achieve a secure flap closure, he or she may see hypotony in the early postoperative period. When starting out with the EX-PRESS device, I suggest suturing the flap securely and then releasing sutures postoperatively.
CONJUNCTIVAL CLOSURE AND POSTOPERATIVE CARE
Conjunctival closure and postoperative care are largely the same with the EX-PRESS device as they are with trabeculectomy. I recommend using topical steroids and antibiotics and performing cycloplegia if necessary. I find that many surgeons who implant the EX-PRESS device are comfortable releasing more sutures earlier, either with planned suture lysis or releasable sutures, starting at 4 to 7 days postoperatively. In general, these are quiet eyes that do not have the same spectrum of postoperative complications as their trabeculectomy counterparts (Figure 5).
EX-PRESS DEVICE PATIENT PROFILE
Once we understand the intricacies of the procedure, it is important to recognize the type of patient who is an appropriate candidate for the EX-PRESS device. Specifically, the device may be indicated for patients who are poor candidates for iridotomy due to risk of bleeding or inflammation. There is very little bleeding with the EX-PRESS device procedure. The EX-PRESS device may also be desirable when there is a need to avoid low intra- and postoperative IOP, such as in cases where there has been a suprachoroidal hemorrhage in the fellow eye. The EX-PRESS device does not need to cause the intraocular drop in IOP that trabeculectomy does, where the chamber shallows and the pressure goes to zero.
OTHER CONSIDERATIONS
Patients with anatomic considerations, such as eyes with a compromised angle, would not be suitable candidates for an EX-PRESS device. I also would not perform this surgery on patients with active uveitic glaucoma or those who are poor candidates for trabeculectomy due to conjunctival scarring or scleral problems.
SUMMARY
I would characterize the ideal first patient for implantation with the EX-PRESS device as someone who meets the surgeon's standards for trabeculectomy, is pseudophakic, has open-angle glaucoma with a wide open angle, and has had no previous conjunctival surgery. In my opinion, this is an excellent place to start in order to ensure the greatest chance for success with the EX-PRESS device. I find the EX-PRESS device procedure to be an attractive alternative to trabeculectomy for appropriate patients, being that it is more controlled, requires less postoperative care, and produces results similar to trabeculectomy. I feel that the EX-PRESS device is a valuable tool in our battle against glaucoma.
Robert D. Fechtner, MD, is the director of the Glaucoma Division at the University of Medicine and Dentistry, New Jersey, and he is a professor of ophthalmology at the Institute of Ophthalmology, both at New Jersey Medical School in Newark. He is a consultant to and has received research support from Alcon Laboratories, Inc., and Allergan, Inc. Dr. Fechtner may be reached at (973) 972- 2030; fechtner@umdnj.edu.
