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Ex-Press glaucoma shunt may be alternative to trabeculectomy
The device is reversible and less invasive than a penetrating filter, surgeons say. Patients can be treated surgically at an earlier stage of the disease.
Patient selection, proper surgical technique and postoperative management are key elements for the successful implantation and function of the Ex-Press Mini Glaucoma Shunt, according to surgeons who have used the device.
The Ex-Press Mini Glaucoma shunt from CIBA Vision is a device that drains the aqueous humor and lowers IOP. It was introduced to the market last year.
John S. Kung, MD, of Staten Island Ophthalmology in New York, was one of the first surgeons to implement the glaucoma shunt in his practice. He has performed 50 cases since fall 2002.
Dr. Kung said implanting the device is easier than a filtering procedure, reversible and patients recover faster. He said he uses it in place of trabeculectomy, and he uses it in most cases requiring one.
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“The device is still on a learning curve, but I would say it has a great role in the armamentarium we can offer patients. There are issues that continue to be stressed before it can be widely accepted, [such as] hypotony and rotation,” he told Ocular Surgery News.
Karanjit S. Kooner, MD, of the University of Texas, who also began using the device late last year, has done 23 cases with it. He said the shunt is not appropriate for every trabeculectomy case, but it may be appropriate for most cases. Typically, he said, the device is best for patients with primary open-angle glaucoma, pseudoexfoliation and pseudophakia.
The shunt lowers IOP by draining aqueous fluid in the subconjunctival space. Patients with previous surgery might sustain erosion, Dr. Kung said.
How it works
The Ex-Press Mini Glaucoma Shunt is a non-valved shunt with a built-in resistance unit that reduces the internal diameter from 400 µm to 50 µm, Dr. Kooner said.
It redirects aqueous humor from the anterior chamber to a conjunctival bleb, according to CIBA Vision information. It is 3 mm long and 400 µm in diameter. Its mechanism is similar to that of a trabeculectomy.
Postop hypotony and rotation of the device are potential complications. Modifications to the device and the implantation procedure are being explored to prevent them, Dr. Kung said. Proper patient selection for the procedure and implantation of the shunt are important for a successful outcome, according to CIBA Vision information.
Patient selection
The Ex-Press Mini Glaucoma Shunt can be used earlier in the course of the disease than trabeculectomy, and it is not only for those in which other treatments have failed, Dr. Kung said. Patients with elevated IOP not controlled with medications or laser are candidates for the shunt, he said.
It is not recommended for patients who have conjunctival scarring from previous surgeries, or who have uveitic glaucoma, aphakic eyes, narrow angles or shallow anterior chambers, he said.
“Initially, surgeons should start using it on pseudophakic patients. I found there is less hypotony with pseudophakic patients than with phakic,” Dr. Kung said.
Selecting patients with untouched conjunctiva is important to avoid fibrosis over the shunt, he said. Scarring around the limbus or an unclear cornea are contraindications for the device, Dr. Kooner said.
Dr. Kung said one advantage of the shunt procedure is that blebs are smaller and shallower.
“Patients are very comfortable with it,” he said.
Surgical treatment
Implantation of the Ex-Press device is easy to learn and fast to perform, Dr. Kung said. The procedure is reversible and leaves multiple entry sites for reimplantation.
“The technique can be done under topical anesthesia or any type of flash retrobulbar procedure the surgeon is familiar with,” Dr. Kooner said.
Dr. Kung described the implantation procedure. He said the lids are retracted and the anterior chamber is filled with viscoelastic. The entry wound is made anywhere from 10 o’clock to the 1 o’clock position. The conjunctiva and Tenon’s capsule are dissected, and a 26-gauge to 30- gauge needle is inserted 1 mm to 1.5 mm posterior to the limbus and parallel to the iris plane. The Ex-Press shunt is inserted into the needle track until it is flush with the sclera. The conjunctiva should be sutured watertight and the anterior chamber filled with viscoelastic, Dr. Kung said.
Both surgeons said the smaller the needle, the less the likelihood for postop hypotony or rotation.
Postop management
Postop management includes monitoring and treating postop hypotony, shallow anterior chamber or rotation.
Postoperatively, patients are given cycloplegic drops. If hypotony occurs, aggressive treatment with topical or oral steroids is recommended, Dr. Kung said.
If the anterior chamber is misshapen or collapsed, viscoelastic can be reinjected, he said.
In the case of pressure spikes, Dr. Kooner makes a paracentesis with a knife and places pressure on the wound to remove some of the viscoelastic.
If the shunt rotates, the plate can cause conjunctival erosion. In this case, the device can be removed and reinserted at a different site on the limbus.
For uncomplicated procedures, patients are followed in the same way as a patient with a trabeculectomy, the surgeons said. Topical steroids and antibiotics are used to quiet inflammation.
Advantages
The glaucoma shunt device has advantages over trabeculectomy, Dr. Kung said. The procedure is quick and reversible, and patients recover their vision faster, he said.
Dr. Kung said he has seen patients with elevated IOP levels quickly drop to target pressures. His most successful case was a patient with an IOP of 70 mm Hg who had remained uncontrolled with treatments. Two months after implanting the shunt, the patient’s pressure was in the high teens, he said.
Technique tips |
| John S. Kung, MD, and Karanjit S. Kooner, MD, have modified their techniques for implanting the Ex-Press device to achieve successful outcomes and avoid potential complications. Using a smaller needle when making the entry wound may prevent leakage and rotation. To implant the shunt, Dr. Kung now uses a 30-gauge needle. Dr. Kooner uses a 26-gauge needle to inject the viscoelastic and a 30-gauge needle to insert the shunt. The smaller the entry wound, the less the possibility for leakage resulting in hypotony. Both surgeons inject the anterior chamber with Viscoat (chondroitin sulfate, sodium hyaluronate, Alcon). Dr. Kung combines this with Healon5 (sodium hyaluronate 2.3%, Pfizer). “In the beginning, we were using 100% Viscoat; now I’m using 75% Viscoat and 25% Healon5, which is a much thicker viscoelastic,” Dr. Kung said. He uses this “viscoelastic cocktail” to prevent hypotony. It is common, he said, to have the IOP drop to 0 mm Hg immediately after surgery. Careful monitoring of patients is necessary to secure that the anterior chamber is stable and does not become shallow. To prevent rotation, Dr. Kung said, he sutures the shunt in place. Dr. Kooner, however, said that proper positioning of the shunt and use of a smaller-gauge needle can help to prevent rotation. |
For Your Information:
- John S. Kung, MD, can be reached at the Staten Island University Hospital, 3930 Richmond Ave., Staten Island, NY 10312; (718) 948-8880; fax: (718) 967-2757. Ocular Surgery News could not confirm whether Dr. Kung has a direct financial interest in the products mentioned in this article or if he is a paid consultant for any companies mentioned.
- Karanjit S. Kooner, MD, can be reached at the University of Texas-Southwestern, Dept. of Ophthalmology, 5323 Harry Hines Blvd., Dallas, TX 75390-9057; (214) 648-4733; fax: (214) 648-2469. Ocular Surgery News could not confirm whether Dr. Kooner has a direct financial interest in the products mentioned in this article or if he is a paid consultant for any companies mentioned.
- CIBA Vision Surgical, distributor of the Ex-Press Mini Glaucoma Shunt, can be reached at 11460 Johns Creek Parkway, Duluth, GA 30097; (678) 415-3711; fax: (678) 415-2320.