Deep sclerectomy with mitomycin C clinically helpful

Study supports mitomycin’s role in weakening ciliary body.

NANTES, France — Despite a number of different approaches to lower intraocular pressure (IOP) in glaucoma patients by non-penetrating trabecular surgery, many have disappointing results. Showing promise, however, is a deep sclerectomy in conjunction with mitomycin C.

For the past 4 years, Philippe Sourdille, MD, an anterior-segment surgeon in private group practice here, and his associates have used a cross-linked hyaluronate implant (Corneal Inc.; Paris, France) in a deep sclerectomy. But what has really made a positive impact on IOP is the addition of mitomycin C.

Study results, which were presented at the American Society of Cataract and Refractive Surgery annual meeting, consisted of 240 consecutive eyes of 181 patients (an equal number of men and women). Mean patient age was 60.7 years, with an average preop IOP of 25 mm Hg. One-third of the eyes had previously been operated on, and the average follow-up time from implant was 25 months.

Mitomycin C cases consisted of 58 consecutive eyes of 50 patients, all of whom had undergone at least one previous surgery. “The angle was open in at least one quadrant,” Dr. Sourdille said. In addition, 57 of the 58 eyes received the hyaluronate implant.

Average follow-up in the mitomycin group was 16.7 months, with a range of 3 to 40 months. “The final IOP was much lower in the mitomycin group compared to the non-mitomycin group, which certainly speaks for the weakening of the ciliary body due to the action of mitomycin C,” Dr. Sourdille said. On the other hand, “final visual acuity was not statistically significant, but was clinically slightly better.”

Perforated eyes

Approximately one-third of the overall study eyes had no conjunctival filtration. “In eyes that had unintentional microperforation, there was no subconjunctival filtration,” Dr. Sourdille said. Specifically, there were 50 cases of unintentional microperforations and 14 cases of intentional microperforations. However, no difference in final IOP was seen between eyes that had a perforation and those that did not. In eyes with subconjunctival filtration, the average IOP was 13.4 mm Hg, compared to 14.4 mm Hg in eyes without perforation. “The percentage of eyes with filtration was 38%, which was slightly higher than the non-mitomycin C group,” Dr. Sourdille said.

In short, “there is clearly a difference” between filtration rates with mitomycin C and without mitomycin, Dr. Sourdille said. “With mitomycin C, there are less vessels. This is due to the application of mitomycin C, whether you put it under the conjunctiva or not.” In the 31 eyes without mitomycin C treatment, the average IOP was 12.9 mm Hg, while in the 27 eyes with treatment, the average IOP was 15.2 mm Hg. “Gonioscopy indicates that you can have an average IOP that is not statistically different, but there may be some clinical difference between a visible sclerectomy and non-visible space,” Dr. Sourdille said.

Indications for a deep sclerectomy with mitomycin C include congenital glaucoma, juvenile glaucoma (under 20 mm Hg) and in high-risk failure cases. “We have had no serious complications, especially on the corneal endothelium side,” Dr. Sourdille said. “But these are incomplete results, and a percentage of patients still require additional treatment.” Still, “the higher tension is only 22 mm Hg, which in this series of cases is reasonable.”

Mechanisms of failure

One possible mechanism of failure in glaucoma surgery is the progressive thickness of the trabecular Descemet’s membrane. “The average thickness is 115 µm, but it seems to increase with time,” Dr. Sourdille said. “I think this may be related to the edematous state of the trabecular membrane. Ultrasonic biomicroscopy (UBM) can also detect some thickening of the trabecular membrane, indicating that less aqueous is coming into the decompression chamber.”

The modification of the decompression chamber over time is a second possible mechanism of failure. “UBM tells us that this chamber becomes slightly smaller with time, which can cause the implant to degrade,” Dr. Sourdille said. UBM also indicates that “if the suprachoroidal space, the subconjunctival space or the intrascleral space can cause aqueous to regress, the main reason for failure usually is a hyper-reflective roof of the decompression chamber, which indicates fibrosis in this space.” Furthermore, “it is interesting to observe that the implant, which is up on the roof when the operation works, is much closer to the suprachoroidal space, as if there was not enough aqueous pushing the implant.”

In addition, massage of the eye or lysis of suture “seems to favor the formation of a pseudofiltrating cyst,” Dr. Sourdille said. “This is why we have to improve the wound healing. This is the reason we started using mitomycin C at the sites where the fibrotic reaction will take place.” In cases of a watertight internal trabeculum, some microperforation is performed. Then, the implant is inserted after application of mitomycin C.

Regardless, “we know that mitomycin C will induce multi-drug resistance, and we can only use it once,” Dr. Sourdille said. Therefore, a 5-FU (5-fluorouracil) releasing implant “might be more interesting because it does not induce resistance and is clinically well known.” In the future, monoclonal antibodies and other drugs may help glaucoma patients. “But, for the time being, mitomycin C, along with non-penetrating trabecular surgery, is clinically helpful,” Dr. Sourdille said.

For Your Information:

• Philippe Sourdille, MD, can be reached at 8 rue Camille Flammarion, 4400 Nantes, France; (33) 251 83 3200; fax: (33) 251 83 8719; e-mail: philippe.sourdille@wanadoo.fr. Dr. Sourdille receives royalties from the cross-linked hyaluronate implant manufactured by Corneal Inc., Paris, France.