COVER FEATURE

Glaucoma

Ex-PRESS mini shunt: new surgical alternative for glaucoma emerges

by Maxine Lipner, senior contributing editor

A new glaucoma surgical device allows some surgeons to avoid trabeculectomy

Instead of opting to perform trabeculectomy to help lower pressure in open angle glaucoma cases, some practitioners are now turning to a miniature device known as the Ex-PRESS mini glaucoma shunt (Optonol, Kansas City, Mo.). The tiny, 3-mm-long device offers a myriad of advantages and is a particular boon for general ophthalmologists, believes Robert L. Stamper, M.D., professor and director of the glaucoma service at University of California, San Francisco.

“Most of the glaucoma surgeries that are performed in this country are done not by glaucoma experts but by comprehensive ophthalmologists,” Dr. Stamper said. “If you’re only doing one, two, or three cases a year, this is an easier operation to perform and the patients are easier to manage after the operation.

The addition of the shunt is less traumatic to the eye than a trabeculectomy. “In a trabeculectomy you’re actually removing tissue (both sclera and iris), which raises the possibility of bleeding and more inflammation,” Dr. Stamper said. He finds there is less inflammation in cases where the Ex-PRESS shunt is implanted compared with a standard trabeculectomy. Dr. Stamper sees this as an important advantage. “When there is less inflammation there is a better likelihood of success, because inflammation leads to scarring and scarring is your enemy here,”

In Dr. Stamper’s experience, the fluid flow through the shunt is also more standardized with a lower risk of hypotony. “The eyes have less likelihood of having too much draining from them than with a trabeculectomy,” he said. “You get just the right amount of fluid flow and you don’t have to guess at it the way you would with a trabeculectomy.”

Mini shunt at work

The ExPRESS shunt works much like a cardiac stent. “It’s shunting fluid from inside of the eye, through the wall of the eye, and draining it underneath the outer covering,” Dr. Stamper said. “So, it works similarly to a trabeculectomy except that it has the advantage of a more controlled flow rate.” Implantation of the shunt is also simpler than performing a trabeculectomy, he finds. “A scleral flap has to be formed just as in a trabeculectomy,” Dr. Stamper said. “Then after one takes a small needle and prepares a pathway for it through the wall of the eye through the sclera, the device is pushed into the eye.” A small barb keeps the mini shunt from being ejected from the eye, while a plate attached to the device keeps it from being pushed into the eye too far. “It’s hard to make a mistake with it,” Dr. Stamper said. After the mini shunt is placed into the eye, a 1/3 to 1/2 thickness scleral flap is then sutured on top to prevent it from dislocating. Dr. Stamper finds that the implantation process takes about 20 minutes in his hands and about 45 minutes when a resident is performing the procedure.

Dr. Stamper has had good results with the Ex-PRESS shunt. He currently has available data from over 40 patients. “About 2/3rds of the surgeries were performed by r residents and fellows and the other 1/3 I performed myself,” he said. “With these patients we have over a 90% success rate at one year.”

So far, Dr. Stamper and his team have encountered few complications. “We’ve had one case with a little bit of bleeding – so, we must have hit a blood vessel when we went into the eye with that needle,” he said. “We’ve also had two patients who’ve had very low pressure for a day or so.” To date, none of the devices has needed to be removed.

He currently opts to use the device for all of his open angle glaucoma patients as well as some patients with chronic angle-closure (without superior synechiae) and exfoliative glaucoma. “I have had better results with it in patients with uveitis or trauma than I have had with my trabeculectomies,” he said.

Weighing in

However, not everybody sees the Ex-PRESS shunt as a beneficial addition to the armamentarium. It seems to Michael S. Berlin, M.D., professor of clinical ophthalmology, Jules Stein Eye Institute, University of California at Los Angeles, that the glaucoma mini shunt has little or no benefit. “In its original iteration it was intended to be a subconjunctival controlled outflow valve for aqueous in the anterior chamber,” Dr. Berlin said. “However it was found not to be different than full-thickness glaucoma filtering procedures with all of their inherent complications, most of which were related to hypotony.” Originally, the device also had a tendency to migrate and because of this, needed to be put under a flap. “The flap better protects it from migration, but it doesn’t add any benefit to a current trabeculectomy procedure, except for a slightly better initial control of outflow,” Dr. Berlin said. However, the difficulty in trabeculectomy surgery is not the initial outflow, it’s the eventual healing of the surgical incision and the amount of outflow control after the healing process is complete. The valve does nothing to alter that situation, he points out. “The current approach, i.e. placement under a flap, has definitely found a niche for this device, but I don’t see that that niche has great advantages over trabeculectomy surgery in the right hands without this,and in the long term, implanted foreign bodies have risk of migration” Dr. Berlin. For his part, going forward Dr. Stamper thinks that new designs will emerge for the mini shunt. “As we go down the road it may be that for your routine glaucoma patients you use one design,” he said. “Then for those that need lower pressures like normal tension glaucoma or, far advanced patients you may use a slightly different design.” He himself currently opts for the Ex-PRESS shunt over trabeculectomy in nearly all cases. “I have switched over,” Dr. Stamper said. “I haven’t done a trabeculectomy now in two years because we have had such good results with the ExPRESS.”

Editor’s Note: Dr. Stamper is a speaker for Optonol and part of their unpaid scientific advisory board. Dr. Berlin has no related professional affiliations.

Contact Information

Berlin: 310-855-1112, Berlin@ucla.edu

Stamper: 415-476-3717, stamper@itsa.ucsf.edu