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Surgeons relate their variations on Ahmed valve implantation technique
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Surgical treatment of glaucoma has advanced in recent years with the advent of minimally invasive stents, but glaucoma drainage devices remain the go-to approach for many surgeons. The Ahmed glaucoma valve from New World Medical is one of the most commonly used drainage devices.
Implantation techniques for the Ahmed valve vary among surgeons, and some have individualized maneuvers to maximize aqueous outflow and minimize postoperative inflammation, device erosion and dislocation, and IOP spikes.
“We are very careful about dissection of the conjunctiva and Tenon’s from the sclera, not only minimizing the bleeding but also making sure the Tenon’s has been separated from the episcleral membrane,” Ying Han, MD, PhD, told Ocular Surgery News. “You don’t want to keep the Tenon’s on the episcleral membrane. That way, you can trigger or increase scar tissue formation.”
Han, associate professor at UCSF School of Medicine, said her technique involves inserting the valve deeper into the sulcus in pseudophakic patients.
“Even for the phakic patient, we sometimes insert the tube into the sulcus as well by inserting 4 mm away from the limbus, through the ciliary body and into the sulcus. We also make a peripheral iridotomy in order to be able to see the tube. With this we haven’t encountered a single tube erosion,” she said (Figures 1, 2 and 3).
Nathan M. Radcliffe, MD, of NYU Langone Ophthalmology Associates, said he makes a 5-mm or 6-mm incision posterior to the limbus, in the superotemporal region.
Image: Han Y
Image: Han Y
Image: Han Y
“It is about as wide as the Ahmed valve itself. I make this incision, and I tunnel to two places. One is behind the eye — that’s where the plate is going to be placed — and the other tunnel is to where the tube will be inserted, at about 12 o’clock,” Radcliffe said. “It gets me exposure to everything I need, unlike the typical fornix-based incision, which is very difficult to access posteriorly because you’re making an incision at the limbus.”
Radcliffe then places the valve 8 mm to 10 mm behind the equator of the globe.
“It is so far back that it’s actually kind of locked into the retrobulbar space. As it would turn out, the plate will just stay back there and not want to come forward. You can test for this in the OR. I’ve never had a case where the valve slipped forward. I do not sew it into place because it won’t come forward,” he said.
Radcliffe creates a long tunnel to place the valve into the anterior chamber.
“When you make a long tunnel, you can often, but not always, skip the step where you sew the tube to the sclera. This is the tube material itself sewn to the sclera,” he said.
The choice of suture is according to surgeon preference, according to Jeffrey R. SooHoo, MD, assistant professor at University of Colorado School of Medicine.
“I tend to use a non-absorbable 8-0 nylon suture. I know surgeons who use an absorbable Vicryl, and that seems to work as well. The plate usually seems pretty stable afterward, but I like having non-absorbable suture myself,” SooHoo said.
Radcliffe said he refrains from using sutures or uses the fewest sutures possible because sutures cause extra trauma to tissues that are dissected during valve implantation. Noting that his sutureless technique has evolved over hundreds of cases, if there is any doubt in his mind as to the stability of the tube placement, Radcliffe said he will place sutures appropriately.
“Suturing is never ideal,” he said. “Placing all those sutures increases the healing time, increases the requirement for anti-inflammatory steroids after the surgery and consumes more time in the operating room.”
Tissue sealants can be used instead of a Vicryl suture to close the conjunctiva, Radcliffe said.
“Closing the conjunctiva can be done with a running Vicryl suture, which is fine. That will cause a lot of inflammation and redness, and cause you to use more steroids. The other option is to use one of two tissue sealants. The first is Tisseel glue (Baxter Healthcare), and the second is the ReSure product (Ocular Therapeutix),” he said.
Sutureless wound closure can reduce operative time and cost, Radcliffe said.
“We do need to be efficient, but we also need to minimize tissue damage and enhance patient comfort, which I think of as safety issues,” he said.
Patch graft
SooHoo said he prefers using Tutoplast pericardium (IOP Ophthalmics) or banked sclera for the patch graft because they are readily available and consistent products, whereas sclera or cornea from an eye bank can be more variable.
The patch graft, too, can be secured without sutures, according to Radcliffe.
“When you make the dissection to get to the superior region of the eye where you’re going to put the tube into the anterior chamber, if you make a nice small dissection and leave a lot of the tissue not dissected, you create a pocket. That pocket will hold the patch graft into perfect place. The patch graft shouldn’t move and also doesn’t need to be sewn down,” he said.
David B. Yan, MD, of the University of Toronto, said his technique avoids the use of a patch graft.
“The technique that I developed involves using a belt loop to bury the tube approximately 250 µm deep within the patient’s own sclera to prevent tube erosion,” Yan said (Figures 4, 5, 6 and 7). “What’s novel about my technique is the tube enters the tunnel 6 mm back from the limbus for full protection from erosion, while a second incision is made 1 mm back from the limbus through which the 22-gauge needle can accurately enter the anterior chamber, avoiding tube contact with both the corneal endothelium and iris.”
Figure 4. Belt loop scleral tunnel made with crescent blade entering 6 mm and exiting 1 mm posterior to the limbus.
Figure 5. Tube inserted into the tunnel and pulled back out for trimming to the correct length.
Figure 6. Needle entry into anterior chamber aiming at mid-peripheral iris to ensure tube stays away from the corneal endothelium.
Figure 7. Wide cross-stitch closure of anterior wound to locally flatten the cornea and prevent erosion starting at the limbus.
Images: Yan DB
The valve enters the eye in exactly the same way as if it were left on the outside of the eye with a scleral patch graft. This enables easier tube placement while providing much longer scleral tunnel coverage of the tube than previous techniques, Yan said.
One benefit of not using a patch graft is avoiding using foreign tissue on the patient’s eye, which can cause inflammation and scarring, Yan said.
Yan said he uses a nylon suture and a modified cross-stitch to close the wound.
“I developed a modified cross-stitch to push the tube further down into the eye at the limbus to minimize the risk of exposure at the limbus, which is the most common area where exposure or erosion of the tube starts. What I did was basically take advantage of the curvature of the eye, so if I place a very large cross-stitch, it will literally push the tube into the eye,” Yan said.
The technique yields a better cosmetic outcome and enhances patient comfort, he said.
“There is no bump or bulge either from the tube or from the patch graft itself,” he said.
Postop prophylaxis
Han and colleagues use mitomycin C during surgery and 1 week to 1 month after surgery. This, she said, significantly reduces scar formation around the plate, therefore preventing a hypertensive phase and improving the long-term outcome.
“Sometimes we do skip the MMC injections if a patient’s IOP is too low or there are choroidals. Most patients receive two injections maximum,” Han said.
Han said she also uses Kenalog (triamcinolone acetonide injectable suspension, Bristol-Myers Squibb) around the plate intraoperatively to minimize scar formation.
SooHoo said he uses aqueous suppressants to manage postoperative IOP spikes and inflammation, which seem to blunt or prevent the hypertensive phase in some patients, according to early “promising” data.
“If there are a lot of inflammatory mediators in the aqueous after a surgery, there might be some benefits in terms of decreased fibrosis and better bleb function ultimately,” SooHoo said. – by Matt Hasson
- References:
- Budenz DL, et al. Ophthalmology. 2015;doi:10.1016/j.ophtha.2014.08.043.
- Christakis PG, et al. Ophthalmology. 2013;doi:10.1016/j.ophtha.2013.04.018.
- Kugu S, et al. Semin Ophthalmol. 2013;doi:10.3109/08820538.2013.807851.
- Pakravan M, et al. Ophthalmology. 2014;doi:10.1016/j.ophtha.2014.03.014.
- For more information:
- Ying Han, MD, PhD, can be reached at UCSF Ophthalmology Department, 10 Koret Way, Room K-327A, San Francisco, CA 94143; email: ying.han@ucsf.edu.
- Nathan M. Radcliffe, MD, can be reached at NYU Langone Ophthalmology Associates, 240 E. 38th St., 13th Floor, New York, NY 10016; email: drradcliffe@gmail.com.
- Jeffrey R. SooHoo, MD, can be reached at Department of Ophthalmology, University of Colorado School of Medicine, Anschutz Medical Campus, 1675 Aurora Court, Mail Stop F-731, Aurora, CO 80045; email: jeffrey.soohoo@ucdenver.edu.
- David B. Yan, MD, can be reached at University Eye Clinic, 700 University Ave., Toronto, Ontario M5G 1Z5; email: dr.david.yan@me.com.
Disclosures: Han reports she has received research funding from New World Medical. Radcliffe reports he is a consultant for Allergan, Iridex, Lumenis and New World Medical. SooHoo reports no relevant financial disclosures. Yan reports he is a consultant for Abbott and Alcon Laboratories.