Damian McNamara

May 08, 2016

NEW ORLEANS — For patients with open-angle glaucoma, the addition of a trabecular implantable stent to phacoemulsification surgery reduces the need for postoperative hypotensive medications, according to a new meta-analysis.

However, in terms of reducing intraocular pressure, "we didn't find any significant difference," said Marko Popovic, BSc, a medical student at the University of Toronto.

"This underlines the importance of not looking only at intraocular pressure" in outcome studies, he told Medscape Medical News.

This lack of reduction in pressure contradicts results from an earlier meta-analysis that showed a reduction in postoperative intraocular pressure when a stent was added to phacoemulsification (PLoS One. 2015;10:e0131770).

But that meta-analysis "included uncontrolled, one-arm studies," whereas ours looked only at studies with a phacoemulsification–stent group and a phacoemulsification-only group, Popovic explained.

"Nevertheless, what we found in both meta-analyses is that phaco–stent is superior to phaco alone for a reduction in medications," he reported here at the American Society of Cataract and Refractive Surgery 2016 Symposium.

The iStent ab interno device (Glaukos Corp.) is indicated for mild to moderate open-angle glaucoma and improves outflow by bypassing the trabecular meshwork.

In their meta-analysis, Popovic and his colleagues identified 52 studies through Medline, EMBASE, the Cochrane database, and major ophthalmology meetings. About half the patients in the phacoemulsification–stent group had one stent, and 40% had two. The number of patients with three stents implanted was very small, so none were included in the analysis.

The mean reduction in medications was significantly greater when a stent was added to phacoemulsification than with phacoemulsifcation alone (1.2. vs 0.66; < .001), but the mean reduction in intraocular pressure was similar in the two groups (5.38 vs 5.30 mm Hg; = .82).

Two Is Better Than One

When the researchers compared outcomes, the mean reduction in intraocular pressure was significantly better with two stents than with one stent (5.28 vs 4.75 mm Hg; P = .008).

"The story with medications is much the same," Popovic reported. Although patients who receive two stents tend to have higher preoperative intraocular pressure, after surgery "there is a significantly greater reduction in the number of medications" in these patients than in those who undergo single-stent implantation (1.05 vs 0.95; P = .006).

The team also looked at the addition of phacoemulsification to stent implantation. Of the 2457 eyes, about one-quarter underwent stent implantation alone and about three-quarters underwent implantation plus phacoemulsification.

The mean postoperative reduction in intraocular pressure was greater with the stent alone than with the combination (10.11 vs 3.82 mm Hg; P < .001). However, there were no significant changes in medication use between the two groups (0.98 vs 0.96; P = .48).

"When comparing phaco–iStent with iStent alone, it's important to keep in mind that this comparison considers two different patient populations," Popovic explained. "People receiving the iStent alone receive it for the pressure issue, and people who receive phaco and iStent obviously have cataracts and elevated intraocular pressure. These are different patients, and you can see a dramatic difference in preop pressure between these comparators."

Postoperative complications associated with stent implantation affected less than 20% of the eyes. The most common events were intraocular pressure elevation, hyphema, and stent blockage.

Even though the pressure is the same, it's the same with less medication.

This meta-analysis shows "that the addition of the iStent, compared with phaco alone, would allow you to decrease medication. Even though the pressure is the same, it's the same with less medication," said study discussant Paul Harasymowycz, MD, from the University of Montreal.

"We also know any additional stent would reduce the medication. For us, on average, each stent reduces the need for about one medication," he told Medscape Medical News.

"The challenge with a meta-analysis is that we're limited by the quality of the data," Popovic pointed out. Most of the studies in the meta-analysis are single-center studies, case series, and retrospective chart reviews. In addition, about 90% of patients in the studies received a first-generation iStent device.

"We implore future researchers to conduct well-designed randomized trials in this setting," said Popovic.

Mr Popovic and Dr Harasymowycz disclosed no relevant financial relationships.

American Society of Cataract and Refractive Surgery (ASCRS) 2016 Symposium. Presented May 7, 2016.


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