Deep sclerectomy still a viable and effective procedure, results show

Surgery’s success hinges on correct dissection of the trabeculo-Descemet’s membrane window and the use of a collagen implant.

Twelve-year results of deep sclerectomy with collagen implant have showed a high rate of success. Mean pressure values are at least as good as those obtained after trabeculectomy with a significantly lower rate of complications, according to a leading glaucoma specialist in Europe.

“When it was first introduced, deep sclerectomy raised a lot of interest but, in fact, has never become so popular. Many colleagues found it too difficult to perform, and some of the published results did not compare favorably with trabeculectomy,” said André Mermoud, MD, of the Clinique Montchoisi in Lausanne, Switzerland. “However, those series were mostly the result of the negative experience of surgeons who did not use the correct technique in the dissection of the trabeculo-Descemet’s membrane.”

Many surgeons are still using deep sclerectomy with a high degree of satisfaction.

“For instance, myself and my colleagues in Lausanne currently use this technique in 98% of our glaucoma patients who need surgery,” he said.

Pearls for a successful surgery

Optonol Ex-PRESS P50 mini glaucoma shunt. Image: Mermoud A

A correct dissection of the trabeculo-Descemet’s membrane window and the use of a collagen implant are crucial steps in the success of the surgery, Dr. Mermoud said. He recommended opening Schlemm’s canal and then detaching the Descemet’s membrane carefully from the corneal stroma. This last maneuver is better done using blunt knives, such as the No. 11 blade placed upside down.

“If the Descemet’s window is well-prepared, if there is a good aqueous outflow and if a collagen implant is used, then the flow from the anterior chamber to the intrascleral space will be more than enough to provide a low pressure. If the membrane, with time, gets thicker and offers a resistance to the outflow, a goniopuncture can be performed easily with a Nd:YAG laser,” he said. “The collagen implant will keep the space open in the scleral bleb for a long period and will also keep the Descemet’s totally transparent for an easy goniopuncture.”

Nd:YAG goniopuncture is performed in 50% to 70% of Dr. Mermoud’s cases after deep sclerectomy. It opens the trabeculo-Descemet’s membrane and allows a good filtration from the anterior chamber to the intrascleral bleb. It is an important procedure because it allows the pressure to be reduced in the long-term follow-up period.

“Results are interesting: Pre-laser IOP in our series was 20 mm Hg and in post-laser IOP was 12 mm Hg,” he said.

Goniopuncture can lead to complications, but only if it is performed too early in the first month after surgery.

“Our 12-year results with this method of performing deep sclerectomy are excellent. The aqueous humor is drained through three to four different pathways, and both early and advanced cases can be treated. Mean IOP in our group is between 11 mm Hg and 12 mm Hg,” Dr. Mermoud said.

The failures reported by some of his colleagues are usually the result of a few recurrent mistakes, he said. The most common is a wrong deep dissection. Often, Schlemm’s canal is not open, and then there is not enough percolation of aqueous through the membrane. Other surgeons do not dissect behind the Descemet’s and only open Schlemm’s canal. This will not produce sufficient filtration and will not allow a surgeon to perform a goniopuncture. Also, many surgeons do not use a collagen implant, and this also reduces the chance of success.

Partial deep sclerectomy with Ex-PRESS

A more recent variation of the technique is the so-called “partial” deep sclerectomy with the implantation of a miniature drainage device.

The procedure entails the creation of an intrascleral bleb in the posterior section, under the superficial scleral flap. Schlemm’s canal is not opened, and the trabeculo-Descemet’s membrane dissection is not performed because the connection between the anterior chamber and the intrascleral bleb is obtained with a mini glaucoma shunt, the Optonol Ex-PRESS P50. The device is inserted under the superficial scleral flap through the trabeculum into the anterior chamber.

Compared with trabeculectomy, in which the filtering bleb is only under the conjunctiva, in partial deep sclerectomy, the filtering bleb will be located in the intrascleral space as well as under the conjunctiva.

Dr. Mermoud and colleagues conducted a clinical, prospective, nonrandomized, unmasked study on 28 eyes of 28 patients in which partial deep sclerectomy with the drainage device implantation was performed. Mean preoperative IOP was 21 mm Hg, and the mean follow-up was 19 months.

At the last visit, mean IOP was 11.5 mm Hg, ranging between 10 mm Hg and 15 mm Hg. Complete success was achieved in 20 patients (71.4%), who achieved stable IOP values of less than 18 mm Hg without glaucoma medication. Of the 28 patients, 25 (89.3%) were a “qualified success,” with IOP less than 18 mm Hg with or without glaucoma medication.

Dr. Mermoud said this procedure simplifies deep sclerectomy and eliminates the need for goniopuncture. It therefore could be used by more surgeons. It is also a promising option for combined glaucoma and cataract surgery. Preliminary results of 25 patients with a mean follow-up of 7 months showed promise.

“There is, of course, a slightly higher rate of complications in combined procedures, and visual recovery is a bit slower. Otherwise, it is an efficient and useful technique,” he said.

A potential complication of the Ex-PRESS is hypertony or hypotony after surgery, which is not common but occurs more often than after deep sclerectomy. At a later stage, if needling is performed and there is a hemorrhage under the conjunctiva, the blood may have access into the anterior chamber through the Ex-PRESS tube.

However, in expert hands, these complications can be easily handled. Further studies with a longer follow-up period are needed to achieve more reliable conclusions, Dr. Mermoud said. – by Michela Cimberle

• André Mermoud, MD, can be reached at Centre de Glaucome, Clinique de Montchoisi, Chemin des Allinges 10, CH-1006 Lausanne, Switzerland; +41-21-619-36-84; fax: +41-21-619-36-28; e-mail: amermoud@montchoisi.ch.