An Introduction to the Ex-Press Mini-Shunt
An Introduction to the Ex-Press Mini-Shunt
Think of it as "trabeculectomy plus."
By Yara Catoira-Boyle, MD
One of the quiet pleasures of being a surgeon is in mastering a new and better technique or in adopting an innovative product or device that makes your job easier while also improving patient outcomes. My journey to acceptance of Alcon's Ex-Press Glaucoma Filtration Device (commonly called the mini-shunt) did not come in a sudden burst of insight; rather, my appreciation of the merits of the Ex-Press developed more slowly, by steps, as I learned to use the device to achieve the best results. Here, I will describe the evolution of my experience with the Ex-Press and offer some guidance on its appropriate use.
First Steps as a Glaucoma Surgeon
Once I finished my glaucoma fellowship, I felt ready to deal with this complicated disease. But after following patients for three years during residency and for a year during fellowship, I was still skeptical that we really needed to subject patients to possibly blinding surgery in hopes of "controlling" a disease that might eventually slowly cost them their vision. True, I had my preceptors' patients to learn from. I was fortunate to be a fellow of the late Dr. Steven Podos and Drs. Janet Serle and Maurice Luntz at Mt. Sinai in New York City. But there were aspects of this disease that I needed to study for myself.
The literature on blindness from glaucoma is actually quite scant. I found only two major retrospective studies done quite some time ago. I have often seen these same studies cited in major articles, so that is all the evidence we have. It is true that 9% to 20% of patients do go blind from glaucoma in one or both eyes, usually over a period of 15 to 20 years.
So, I had my patients teach me. Now, eight years after my fellowship, I fully recognize that our primary task is to safely and effectively lower intraocular pressure. Still, as glaucoma surgeons, we are often faced with the difficult decision of recommending a trabeculectomy to our patients, a surgery that, frankly, no glaucoma specialist would like to have done to their own eye.
My Ex-Press Learning Curve
When I first heard about the Ex-Press mini-shunt, probably around 2006 at the AAO exhibitor hall, I was intrigued. As time went on, I continued to hear more and more about good results from surgeons who had learned to use the Ex-Press safely and effectively. I then made the decision to use the Ex-Press at our VA hospital in Indianapolis.
The idea of a controlled-size sclerostomy brought to mind flashes of many times watching the resident trying to get just the right amount of iris out of the eye to perform an iridotomy and seeing the chamber go flat. Then, I'm refilling it and at times vitreous comes out. Oops, now it becomes a scissors vitrectomy and frustration ensues.
In the summer of 2008, we ordered a few Ex-Press minishunts and I decided to do only Ex-Press-assisted trabeculectomy surgery, for lack of a better description of the procedure. True, it's not actually a trabeculectomy any more, since we are not removing — but rather bypassing — the trabecular meshwork. However, I still write "trabeculectomy with Ex-Press shunt" on my operative reports.
Prior to our first case, the resident and I read the instructions and watched a video. We had two cases scheduled. For the first one, we entered the eye with the 27-gauge needle through Descemet's membrane. The tissue opened horizontally in both directions. That meant no Ex-Press for this patient as we converted the procedure to regular trabeculectomy. From this experience, I learned that too anterior is not good.
In the second case of the day, after inserting the Ex-Press successfully through the scleral spur, I proceeded to do the usual refilling of the chamber to check flow after the scleral flap was sutured. There was no flow. The cornea became edematous and white, but with no flow. We cut one of the two sutures (see below for my technique) and lifted the flap to see the Ex-Press. There was still no flow. So I left the flap sutured only in one side. The next day, of course, we saw a flat chamber. The lesson to me was that, with the patient lying down, the fluid mechanics were not the same due to the Ex-Press lumen size.
Success with Ex-Press
Since then, we have performed more than 50 implants at our VA hospital. I know the number because we presented our partial experience at ARVO 2010. In my practice, I do not perform trabeculectomies regularly any more. I use the Ex-Press.
My biggest reason for not going back to trabeculectomies is the fact that I no longer stay awake at night wondering what the patient is going to look like in the morning. I have used mostly the R-50 and recently the P-50 in some cases, and sometimes even the P-200. I'll illustrate later with some individual cases.
My Ex-Press Technique
I start by placing a bridal peripheral corneal suture that I attach to the inferior drapes with steri-strips and also place a corneal protector made of a piece of Wek-cel sponge with some "cornea coat."
I perform a limbus-based conjunctival flap. I realize that is not the case with most glaucoma surgeons who use this procedure. My preferred technique minimizes the risk of wound leaks, and I have never had one. I like small incisions and careful conjunctival manipulation. On the other hand, a fornix-based flap allows much better visualization for the beginning surgeon and minimizes the needs for assistance during surgery.
In my opinion, the closure needs to be watertight, which can be attained with a variety of techniques. There is also a tendency among some surgeons to think that the conjunctival suturing used in the first technique might scar and act as a barrier, or "ring of steel."
Hemostasis is done with wet-field cautery, and I avoid excessive cautery to minimize shrinkage of sclera. Then, I apply mitomycin-C at 0.2mg/ml for three to five minutes. I use it for three minutes on older Caucasian patients and up to five minutes on younger patients, African-Americans and reoperations to prevent scarring. I like to put the MMC in a cup filled with tiny pieces of Wek-cel pledgets and I stuff anywhere from six to 10 pledgets over a wide area of the superior bulbar conjunctiva.
Once these are removed, we irrigate the area with two small bottles of BSS. Then I mark a square 3 x 3 mm flap and dissect it at 1/2 sclera thickness up to the "gray line." At that point, I perform a paracentesis and refill the anterior chamber with BSS, if needed. Then I inspect the shunt by removing it from its guiding injector with Hoskings forceps and irrigate with BSS and put it back in place.
After that, I use a 27-gauge needle to enter the eye at the level of the scleral spur or the gray line posterior to the peripheral cornea. I like to see the needle enter the anterior chamber to judge if it is in the right location. Then, I insert the Ex-Press and inspect it in the anterior chamber. Following that, I proceed to close the scleral flap with two sutures.
I use releasable sutures if I think I will not be able to see my sutures for laser suture lysis postoperatively. That technique is indicated for patients with thick Tenon's capsule, younger patients, African-Americans or reoperations. I close the conjunctiva and Tenon's capsule with one 8-0 Vicryl suture on a BV needle, running, separate layers, non-locking bites. I inject 1 cc of subconjunctival decadron and patch the eye with Maxitrol ointment, along with atropine if the patient is phakic.
Guidance on Postoperative Care
I see patients on days one, eight, 15 and 22. These visits are quick, for vision and pressure. After that, if the IOP reduction is satisfactory, I may space out visits to two weeks. The regimen is prednisolone acetate 1% drops for a total of about two to three months. I start the drops at anywhere between four to 10 times a day. It really depends on how the bleb looks on day one and on the healing features of the patient, as noted above.
The tapering is never "blind." I cut down on drop frequency as I see that the patient is maintaining stable IOP. I also use an antibiotic for the first week and continue maxitrol ointment bid and then bedtime, until it runs out. If the phakic patient has a stable anterior chamber, there is probably no need for atropine beyond the first week. The time for suture lysis or releasing sutures is during the first month. Hence, there is a need to see patients quite often during this period. Most of the time, patients have IOP on day one between 7 and 12 mm Hg. Occasionally the IOP is lower. I have noticed releasable sutures usually render IOP lower because the flap is not as tightly tied.
Ex-Press Advantages Over Trabeculectomy
► The controlled size of the sclerostomy allows for more uniform results as far as IOP reduction.
► The chamber doesn't tend to flatten during surgery, saving on time refilling the chamber and on the use of viscoelastic.
► With no need to perform an iridotomy, I save time and decrease postoperative inflammation.
► I have experienced a greatly decreased rate of hypotony with the Ex-Press (see the chart below). This is a major advantage of the Ex-Press. We often encounter hypotony after trabeculectomy and sometimes after Ex-Press implantation but it is usually transient with the Ex-Press. When hypotony becomes chronic or nonresolving, visual acuity suffers permanently.
Concerns Compared to Trabeculectomy
■ Cost of implant. We would like to think cost is not a factor, but this concern is real. Some insurance carriers require a letter of necessity. As I try to be conscious of healthcare costs, I really don't feel using the Ex-Press is a waste of resources. Devices are regularly used for cataract surgery to improve outcomes. I see the Ex-Press shunt the same way. Alcon is obviously working hard to resolve this. This surgery still has a T-code.
■ Some have wondered if you can needle these blebs. You absolutely can. The precondition for needling any bleb in my opinion is an open sclerostomy, as you try to brake the episcleral scarring. I have done this and it works very well.
Tips for Ex-Press Success
The following are some of the recommendations I can make with confidence, based upon my own experience over the last two years.
■ Once the Ex-Press is in the eye, always inspect it and make sure you can see it in the anterior chamber. I have on occasion removed it and performed another needle tract in a better location, usually more anteriorly, if I can't see it anterior to the iris. On one occasion, a patient with a large area of corneal pannus precluded direct visualization and fortunately the shunt turned out to be in good location. But usually you can see it.
Nevertheless, if on the next day the tip of the shunt is buried into the iris, don't despair, I have still seen perfect IOP control in that situation. I have also used the YAG laser for an iridotomy at the location of the shunt, and once I took a patient back to the OR and performed an iridectomy using the anterior vitrector. Both patients had high IOP before these procedures and the IOP came down after.
■ There is no need for viscoelastic during surgery and I don't leave it in the eye routinely. I fill the eye with BSS at the end. Healon GV may be used if necessary in the postoperative period without concern for IOP spikes. I do not recommend Healon 5 for this purpose.
■ Hypotony can happen, but it's very rare. It's usually related to releasable sutures in my most recent experience.
Studies: Ex-Press vs. Trabeculectomy
The published literature has shown the Ex-Press to be equivalent to trabeculectomy in IOP control, and some reports have shown a decrease in complications. We recently reviewed our experience, comparing trabeculectomy with Ex-Press outcomes, and presented it at ARVO 2010. We showed follow-up data for the two groups at six months. More data will follow. As the chart above indicates, the rate of hypotony was clearly decreased, though the P-value was not significant due to the small power of the study.
Review of Several Ex-Press Cases
A 28-year-old monocular African-American female, with h/o blind OD from traumatic retinal detachment, with hand motion vision (Figure 1). Her one good eye was 20/20 with a -19.00 refraction, axial length of 31 mm. IOP was controlled to the upper teens from the upper 20s with medications with moderate superior and inferior arcuates. Optic nerve cupping at 0.9 with OCT average NFL thickness of 66. Unable to comply with eyedrops, as she told me. She elected to have surgery.
Figure 1. A 28-year-old African-American female high-myope with diffuse but thick bleb at postop month three. PHOTO'S COURTESY OF THE AUTHOR
We had a very long discussion about the postop use of drops. I did phaco/IOL/Ex-Press with MMC (five minutes) on her with the above technique, with one releasable suture. Her IOL power was 5 D. IOP was between two and four for two weeks; I added Durezol BID to the PredForte and Nevanac for some retinal edema by OCT with VA of 20/70 and a hyperopic shift. At week five, IOP was 7 mm Hg with perfect diffuse superior bleb, but very thick Tenon's capsule with no view of the flap. At week six, IOP was 15, so I released the available suture and IOP came down to 7. It stayed there for two weeks and Durezol was discontinued. At three months, VA was 20/20 uncorrected, with IOP of 8.
A 59-year-old Caucasian male attorney with advanced open-angle glaucoma (Figure 2) was referred with dense inferior arcuate defects in both eyes. I followed him for six years with stable HVF and IOPs between 8 and 12 mm Hg on maximal medical therapy and SLT twice in each eye. Two years ago, his visual fields started to worsen and his IOP climbed to 15. We proceeded with both eyes Ex-Press, about three months apart. His IOP was around 6 from day one. I performed laser suture lysis in both eyes. His IOP and HVF have been stable (5-7 mm Hg) for the last two years. VA is 20/20 in both eyes.
Figure 2. A 59-year-old Caucasian male one year after Ex-Press implantation, showing thin, avascular, diffuse bleb.
An 85-Year-old Caucasian male veteran presented in 2003 with CF vision both eyes from dry macular degeneration, ON cupping around 0.85, worse left eye, and IOP in the 30s in both eyes. IOP was controlled in the upper teens for some time with medications, but around 2006 it went up to the mid 20s despite MMT and SLT.
We proceeded with phaco/trab/MMC left eye at the time. He had hypotony postoperatively, with choroidals that even though not very large, hugely impacted the only vision he had — his peripheral vision. The choroidals would resolve and then return with IOP around 5 to 6 over the years. He refused trabeculectomy on the right eye for a long time. We removed the cataract on the right eye. Eventually, with IOPs in the mid 20s, we proceeded with diode CPC in July 2008.
The IOP never came down and he developed iritis and some subjective visual loss. Finally, he elected to have an Ex-Press/MMC left eye in January of 2009. At the time, he asked for surgery as his once-better right eye vision was deteriorating. Postoperative period was uneventful with IOP in the low teens. On his last exam recently, his IOP was 12 right eye and 9 left eye; the visual deterioration has stabilized.
A 53-year-old Caucasian male monocular due to ocular trauma both eyes, with 20/400 in only left eye (Figure 3). He presented with IOP in the 30s in 2003. The IOP was controlled in the low teens on MMT for some time, until the vision started to deteriorate and did not improve much after cataract extraction. In July 2009, he underwent Ex-Press shunt left eye, and did well initially, but IOP eventually climbed back to low 20s. We then needled with MMC in January 2010. The IOP responded initially and then elevated again. Finally, I implanted a second Ex-Press in March 2010, a P-50, and his IOP has been 8 since. This time, I used two releasable sutures and released them within one month.
Figure 3. A 53-year-old Caucasian male with two Ex-Press shunts, done nine months apart, now with perfect IOP control.
In summary, I believe as we move forward in the search for a better glaucoma surgery, the use of devices will increase. The Ex-Press shunt is a step towards safer filtering surgery for patients who require IOP in the single digits. The TVT study showed decreased complications and similar IOP with Baerveldt shunts compared to trabeculectomy. In my hands, I appreciate IOP control with the ideal of minimizing complications. I believe that for the general ophthalmologist who is already performing trabeculectomies, the step to Ex-Press will be an easy one and a way to standardize their surgeries. Complications still happen, but our study showed decreased rate of severe and prolonged hypotony, with control of intraocular pressure similar to trabeculectomy. OM
|Yara Catoira-Boyle is a glaucoma specialist at the Indiana University School of Medicine (IUSM) and Indianapolis VA Medical Center. She can be reached via e-mail at: firstname.lastname@example.org.|
Ophthamology Management, Issue: October 2010