For the past 7 years, I have been using the EX-PRESS Glaucoma Filtration Device (Alcon Laboratories, Inc., Fort Worth, TX). This article describes my clinical experience with the EX-PRESS device in glaucoma management, as well as my recommendations for incorporating it into the glaucoma surgeon's armamentarium.
WHERE THE EX-PRESS DEVICE FITS
Initially, I reserved my use of the EX-PRESS device for eyes with advanced disease. As my comfort with the EX-PRESS device has grown, however, I have expanded my use of it. The EX-PRESS device can be very effective as the first incisional surgery after laser trabeculoplasty and medications, and its ease of insertion also makes it a great surgical option for glaucoma residents.
Figure 1 shows a postoperative bleb after implantation of an EX-PRESS device. It demonstrates the ultimate goal of this implant: a low, diffuse bleb with a low IOP. The EX-PRESS device is designed to direct aqueous flow posteriorly, which may help avoid small cystic blebs that are prone to endophthalmitis-related blebitis (Figure 2).
INCORPORATING THE EX-PRESS DEVICE INTO CLINICAL PRACTICE
Placement
In order to implant the EX-PRESS device, the surgeon
creates a partial-thickness (approximately 300-um) scleral
flap, located either at the fornix or limbus (I have placed
it in both positions with equal success) (Figure 3A). The
scleral flap for the device can be triangular-trapezoidal
or rectangular, but it must be large enough to cover the
plate of the implant. I place the EX-PRESS device exactly
at the grey line, parallel to the iris (Figure 3B). Then, I resecure
the scleral flap to the globe, tying it only moderately
tightly in order to leave adequate posterior leakage.
In the immediate postoperative period, the releasable or
laserable sutures placed close to the limbus control the
eye's IOP and may be adjusted as necessary. Using these
sutures requires their removal at the slit lamp or laser
suturelysis in the postoperative period in order to titrate
the desired amount of aqueous outflow and IOP.
Patient Candidates
The EX-PRESS Glaucoma Filtration Device is indicated
to reduce IOP in glaucomatous patients where medical
and conventional surgical treatments have failed. For surgeons
first starting to implant the device, I feel that the
perfect patients with whom to gain experience are
pseudophakes with temporal clear corneal incisions and virgin superior conjunctiva. Other appropriate candidates
are virgin eyes with deep chambers and open
angles that clearly require surgical glaucoma treatment,
eyes that have failed a combined phaco/trabeculectomy
(ie, “triple”) but have enough room temporally for placing
the device, and/or eyes in which the surgeon would
prefer to place a tube shunt.
The EX-PRESS Device Versus Trabeculectomy
What is the difference between performing trabeculectomy
and implanting the EX-PRESS device? Trabeculectomy
involves removing a piece of the trabecular
meshwork and then performing an iridectomy. It is a difficult
procedure to standardize from case to case; the
amount of aqueous efflux will vary based on the amount
of tissue excised by the surgeon. The tightness of the flap
sutures also affords additional variability. Lack of standardization
is the main problem with trabeculectomy.
The EX-PRESS Glaucoma Filtration device has a 50-μm lumen that shunts the aqueous from the anterior chamber to underneath Tenon's capsule and conjunctiva. The device is small and takes up very little geography on the globe (Figure 4A-D). The EX-PRESS device provides a more consistent flow of aqueous than trabeculectomy, and the bleb is low and diffuse. The EX-PRESS device is also useful in scarred eyes, because it only needs a small amount of untouched conjunctiva for placement.1 I consider the EX-PRESS device to be a better alternative than repeating a trabeculectomy where one has already failed. The EX-PRESS device's small size gives the surgeon the flexibility to achieve a low IOP while avoiding the larger tube shunts (although large shunts are still a viable option later, should the EX-PRESS device fail).
INSERTION OF THE EX-PRESS DEVICE
My colleagues and I recently published our intermediate-term results after implanting the EX-PRESS device under a scleral flap in eyes that had undergone a previous operation.2 The study involved 100 eyes of 100 patients who we observed for more than 2 years. The mean preoperative IOP was 27 ±9.2 mm Hg with the use of 2.73 ±1.1 drugs, and the IOP fell to 14.02 ±5.1 mm Hg with the use of 0.72 ±1.06 drugs at the most recent follow- up visit, P<.001 (the mean follow- up period was 27 ±13.2 months). Also, the subjects required significantly less topical glaucoma medication. The rate of complete success (defined as an IOP of 5 to 21 mm Hg without medication or surgical intervention) at 1, 2, and 3 years was 79.8%, 64.4%, and 55.9%, respectively. A subset of patients who had undergone previous cataract surgery achieved a success rate of 59.6% by the third year, and eyes with previous trabeculectomies reached 65.3% success.
The causes of failure (having to repeat the surgery) with the EX-PRESS device included uncontrolled IOP (16%), persistent hypotony (1%), and needling of the bleb (4%). We were able to conclude that the EX-PRESS device implanted under a flap is a safe and effective form of glaucoma surgery in eyes that have prior scarring.
SURGICAL PEARLS
My colleagues and I have used a number of implantation techniques in our study of the EX-PRESS device. For limbusbased flaps, I open the conjunctiva and tenon's approximately 10 mm posterior to the limbus under the “blitz” anesthesia technique (topical Xylocaine jelly [Astrazeneca LP, Wilmington, DE] followed by intracameral 1% lidocaine) (Figure 5). After I make the flap, I fill the anterior chamber with balanced saline solution. It is important to never implant the EX-PRESS device when the chamber is shallow; the pressure should be at least 20 mm Hg.
After suturing the flap over the EX-PRESS device, I assess how much flow there is. Filling the eye to firmness with balanced salt solution should cause leakage around the flap. When the eye is soft (saline can be removed from the eye via pressing on the paracentesis), there should be very little flow. A suture will help control the IOP in the postoperative period and can be released if the IOP appears stable or not low enough. Although I prefer a fornix-based flap for most cases, in patients who are elderly, not careful, or who travel a distance to the surgery center, I often use a limbal-based flap with one releasable suture, because there is only one stitch for the doctor to remove. It does not matter what kind of suture you use, only that the wound is watertight. For my limbal-based flaps, I prefer to lock Tenon's capsule with a continuous running locking suture (8–0 vicryl [Ethicon, Inc., Somerville, NJ]) in one direction that I then exteriorize through the conjunctiva and run in the opposite direction for watertight closure of conjunctiva. For a fornix-based closure, I prefer interrupted 10–0 nylon.
CONCLUSION
It is important to be able to offer glaucoma patients surgical treatment options, especially those who a procedure and medications have already failed. The strategy for managing patients who have experienced a failed trabeculectomy or corneal scarring can be challenging. Do we restart their medications? Repeat the trabeculectomy? Implant a large shunt? Are there other options? The EX-PRESS device offers many solutions: it is stainless steel, inert, and compatible with MRIs. The device stays where it is placed and does not cause inflammation. I have come to rely on the EX-PRESS device as yet another tool to help me manage patients with uncontrolled glaucoma.
Marlene R. Moster, MD, is a professor of ophthalmology at the Thomas Jefferson School of Medicine and is an attending surgeon at Wills Eye Institute, both in Philadelphia. She is a clinical investigator for the EX-PRESS Glaucoma Filtration Device. Dr. Moster may be reached at (484) 434-2717; marlenemoster@aol.com.
Kathryn B. Freidl, MD, is a glaucoma fellow at Wills Eye Institute in Philadelphia. She states that she has no financial relationships to disclose. Dr. Freidl may be reached atkfreidl@gmail.com.
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