Glaucoma device implanted under scleral flap lowers IOP

A large case series found that the Ex-PRESS microshunt, implanted alone or combined with phaco, had a high success rate.

The Ex-PRESS microshunt is effective as a primary glaucoma treatment, lowering IOP and reducing medication in glaucoma cases treated with the shunt alone or in combination with phacoemulsification, according to a study.

Peter A. Netland

However, cataract surgery combined with the Ex-PRESS glaucoma micro-shunt (Optonol) implantation appeared to have an impact on bleb function, affecting IOP results postoperatively in combined cases, according to Peter A. Netland, MD, PhD.

The combined microshunt and cataract surgery group had a higher mean postop IOP at five of 12 time points and needed significantly more medication at seven of 12 time points than the group with the Ex-PRESS alone, the study found.

“At individual time points, many times the pressure control was not as good after a combined surgery as it was after the Ex-PRESS implant alone, indicating that somehow the cataract surgery can affect bleb function, maybe reducing bleb function slightly if you do cataract surgery combined with the Ex-PRESS under scleral flap,” Dr. Netland said. “The overall result is very similar between these two groups, but there are some subtle, statistically significant differences.”

Dr. Netland, who conducted a study of the device with colleagues, said that while the Ex-PRESS shunt had good pressure-lowering and medication-reducing effects both with and without cataract surgery, surgeons should be aware of variation in results when combining it with cataract surgery.

“These kinds of differences have also been observed with trabeculectomy combined with cataract surgery,” he told Ocular Surgery News. “So we felt that it was very interesting, but comparable, in fact, to the situation with the gold standard of trabeculectomy combined with cataract surgery, where oftentimes you’ll see a little bit higher IOPs, maybe a little bit more medication. … This is just something to keep in mind with this type of surgery.”

Study design, results

The retrospective comparative study examined 345 consecutive eyes. Of those, 231 eyes were implanted with the Ex-PRESS device under a scleral flap alone and 114 eyes were implanted with the device under a scleral flap combined with phaco. Both groups received intraoperative mitomycin C.

Patients in the Ex-PRESS-alone implant group were followed from 1 to 46.2 months, and patients in the combined microshunt/cataract surgery group were followed from 1.9 to 46.2 months.

By 3 years postop, surgical success was 94.8% in the Ex-PRESS-alone group and 95.6% in the combined group.

The study found that IOP and number of glaucoma medications were significantly lowered from baseline in both groups. Change from baseline IOP was significantly greater in the Ex-PRESS-alone group when compared with the combined group (P < .001). The combined group had a lower baseline IOP and higher IOP at some postoperative time points, Dr. Netland noted.

He and colleagues had conducted an earlier study comparing the Ex-PRESS implant under a scleral flap to trabeculectomy, with 50 eyes implanted with the glaucoma device and 50 eyes undergoing filtration surgery. The Ex-PRESS microshunt implantation is considered a trabeculectomy-like procedure with fewer complications, which prompted the comparison of the two in the earlier study, Dr. Netland said.

In that study, he and colleagues found that results were comparable for the device and filtration surgery. The main difference was a lower rate of early postoperative complications in the Ex-PRESS implant cases.

Complications

According to the latest study, the most common device-related complication in both groups was tube obstruction in six eyes. Those eyes were successfully treated with YAG laser. In the Ex-PRESS only group, one device was blocked with vitreous and was treated by YAG laser. Elevated IOP and a flat bleb were observed in the other patients later in the postoperative period. In four out of five of these eyes, mild chronic inflammation was observed. Visible obstruction was not seen in those eyes, “although Nd:YAG laser treatment of the tube tip (1 to 2 mJ) resulted in a dispersion of whitish particles near the tube tip, elevation of the bleb and reduction of the IOP,” the study said.

In the first week in the Ex-PRESS-alone group, 36 eyes had hypotony; in the same time period in the combined group, nine eyes had hypotony. Every case of hypotony resolved spontaneously in the early postop period.

Dr. Netland said the large number of subjects in the study accurately demonstrated the Ex-PRESS microshunt’s low complication rate.

“Both patients and surgeons are looking for a safe, effective and predictable surgical procedure, and this device seems to be a step in the right direction,” he said. “It can be viewed as a modification of trabeculectomy in some ways, or it can be viewed as its own procedure in other ways. There is no trabeculectomy in the sense that no trabecular tissue is removed, but however you look at it, certainly it’s been a helpful technique to add to our management of patients for their primary surgeries.” – by Erin L. Boyle

References:

• Kanner EM, Netland PA, Sarkisian SR Jr, Du H. Ex-PRESS miniature glaucoma device implanted under a scleral flap alone or combined with phacoemulsification cataract surgery. J Glaucoma. 2009;18(6):488-491.
• Maris PJ Jr, Ishida K, Netland PA. Comparison of trabeculectomy with Ex-PRESS miniature glaucoma device implanted under scleral flap. J Glaucoma. 2007;16(1):14-19.

• Peter A. Netland, MD, PhD, can be reached at University of Virginia School of Medicine, Department of Ophthalmology, P.O. Box 800715, Charlottesville, VA 22908-0715, U.S.A.; +1-434-982-1086; e-mail: dap2b@virginia.edu.