Ex-PRESS Shunt 3-Year Outcomes Don't Top Trabeculectomy

Miriam E. Tucker

March 10, 2014

Washington, DC — The Ex-PRESS glaucoma filtration device provides little additional long-term benefit over conventional trabeculectomy, 2 new studies show.

One study suggests that Ex-PRESS is not more cost-effective than conventional trabeculectomy; the other showed no significant difference in clinical outcomes between the 2 procedures. Both studies provided 3-year data.

The findings from the studies were presented here at American Glaucoma Society 24th Annual Meeting. The results fuel a decade-long debate that has been taking place in the glaucoma world.

"Many people believe the Ex-PRESS shunt is a glorified expensive trabeculectomy. Cost is a key issue," said Carla Siegfried, MD, from the Department of Ophthalmology and Visual Sciences at the University of Washington in St. Louis, Missouri.

 
Many people believe the Ex-PRESS shunt is a glorified expensive trabeculectomy. Cost is a key issue.
 

There are advantages to the Ex-PRESS because of short-term reduced complication rates and quicker recovery, but "at what cost?" she asked. Dr. Siegfried was not involved with either study, but was an investigator on recent work that produced similar 2-year results (Am J Ophthalmol. 2014;157:433-440.e3).

The implantable stainless steel Ex-PRESS glaucoma filtration device was approved by the US Food and Drug Administration in 2002. It reduces intraocular pressure by diverting excess aqueous humor from the anterior chamber to a subconjunctival bleb.

The shunt was initially designed to be placed under the conjunctiva, but that process produced a high complication rate, so the technique was modified and it is now placed under a scleral flap and used in conjunction with mitomycin C. "Then it became like a trabeculectomy," Dr. Siegfried explained.

Results from the first study were presented by Stella Hennen, MD, from the glaucoma service at the Hennepin County Medical Center in Minneapolis.

Her team conducted a retrospective chart review of 3-year postsurgical outcomes for 343 patients who had glaucoma procedures performed from 2006 to 2012.

3-Year Postsurgical Outcomes

Ninety-five patients underwent Ex-PRESS implantation, 89 underwent trabeculectomy, 90 underwent Ex-PRESS implantation with cataract extraction, and 69 underwent trabeculectomy with cataract extraction.

Costs were examined from a payer prospective, based on Medicare allowable charges. A complete success was defined as a procedure with no additional costs. A qualified success included the costs of additional glaucoma medications, and a failure included the cost of additional medications plus additional surgery.

The cost-effectiveness of an intervention was determined by comparing the incremental cost-utility ratio with the willingness of policy makers to pay to gain a quality-adjusted life year, typically set at $50,000. These were calculated using beginning and ending mean deviation scores and beginning and ending visual acuity scores.

 
These findings indicate that the Ex-PRESS is not a cost-effective alternative to trabeculectomy.
 

Postoperative success and failure rates, visual acuity, mean deviation of visual fields, and number of glaucoma medications before and after the procedure were similar in the 4 groups. There were no differences in visual acuity quality-adjusted life years or mean deviation visual field quality-adjusted life years.

The incremental cost of care over 3 years was $784.08 higher for Ex-PRESS alone than for trabeculectomy alone. When cataract extraction was involved, Ex-PRESS was $495.16 higher because of the cost of the Ex-PRESS shunt itself, Dr. Hennen reported.

"The question is, to pay or not to pay," she said.

The incremental effectiveness of Ex-PRESS alone and in combination with cataract surgery was lower than for trabeculectomy, at –0.02 and –0.07, respectively.

"These findings indicate that the Ex-PRESS is not a cost-effective alternative to trabeculectomy," said Dr. Hennen.

After the presentation, Alcon consultant Steven Sarkisian Jr., MD, director of the glaucoma fellowship at the Dean A. McGee Eye Institute and clinical associate professor of ophthalmology at the University of Oklahoma in Oklahoma City, noted that a recent study of prospective data by his group showed faster visual recovery with the Ex-PRESS (Am J Ophthalmol. 2014;157:433-440.e3).

"In a cost analysis, there are certain intangibles that we seem to ignore," he said. "If someone's visual acuity recovers faster — and we are in the business of helping people's vision — that's something we really need to think carefully about."

 
These findings indicate that the Ex-PRESS is not a cost-effective alternative to trabeculectomy.
 

He added that in his 11 years of experience with the Ex-PRESS, he has seen less pressure variability early on and less interoperative variability. "If you have a busy operative day, it actually does make that day more efficient. If you think about the cost-effectiveness of using operating room space and paying staff — that's actually fairly significant. All the opportunity costs need to be evaluated."

"I, like you, was a strong proponent of the Ex-PRESS before we did this study," said Dr. Hennen, noting that the data showed no difference in visual recovery or surgical time.

But Dr. Sarkisian said that prospective studies have backed up his experience, whereas the current findings were retrospective. Dr. Hennen acknowledged that this is a limitation of the study.

1-Year Differences Gone at 3 Years

The second study, an extension of previous 1-year data, was presented by Johanna Gonzalez, MD, from Toronto Western Hospital and the University of Toronto.

The initial study involved 63 patients; 32 randomized to receive Ex-PRESS and 31 randomized to conventional trabeculectomy. At 3 years, 23 Ex-PRESS patients and 20 trabeculectomy patients remained in the study.

In this study, complete success was defined as intraocular pressure of 5 to 18 mm Hg and a 20% reduction in pressure from baseline without medication. Partial success was the same, but with medications.

At 3 years, there was no difference between the treatments in rates of complete success (P = .9) or rates of partial success (P = .08).

At a mean follow-up of 3 years, mean intraocular pressure was higher in the Ex-PRESS group than in the trabeculectomy group (13.6 vs 10.24 mm Hg). With both treatments, pressure was significantly lower at all time points than at baseline.

The significantly lower pressure in the trabeculectomy group at 3 years should be interpreted with caution "because 13 patients haven't yet reached the 3-year mark," Dr. Gonzalez explained.

There was no difference in the proportion of patients using medications at 3 years in the 2 treatment groups; about half of each group were. Mean visual acuity, which was better with Ex-PRESS at 2 years (0.40 vs 0.77; P < .05), did not differ significantly at 3 years.

More Ex-PRESS patients than trabeculectomy patients required additional glaucoma surgery (26% vs 15%), but complication rates did not differ at 3 years, Dr. Gonzalez said.

Despite the equivocal data, Dr. Siegfried said she still uses the Ex-PRESS for certain types of patients, such as those on anticoagulant therapy because the incision is smaller, meaning less risk of bleeding, and those who are also undergoing cataract extraction because there might be less inflammation.

But these factors haven't been proven, she told Medscape Medical News.

"I think there are some theoretical advantages," she said. However, she cautioned that in previous studies, "none of the subgroup analyses were adequately powered" to confirm potential benefit over trabeculectomy. "Whether these advantages are real and can be proven by scientific studies remains to be seen."

Dr. Hennan and Dr. Gonzalez have disclosed no relevant financial relationships. Dr. Sarkisian is a consultant for Alcon. Dr. Siegfried has received grant support from Alcon and the National Eye Institute, and will soon be a consultant for Allergan.

American Glaucoma Society (AGS) 24th Annual Meeting: Abstract 5, presented February 27, 2014; abstract 29, presented March 1, 2014.

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