TUESDAY, Nov. 13 (HealthDay News) -- Tiny devices that allow fluid to drain from the eye could reduce the dangerously high pressure in the eyes of glaucoma patients.

These "micro-stents" -- including one that's newly available and others that are under development -- come with caveats. They may not protect the eyes from glaucoma in the long term, and it's unclear if they're effective when not used in conjunction with cataract surgery.

Still, research continues. This week, scientists released a preliminary study of one type of micro-stent that says it allowed most patients to avoid having to take eye drops to control their eye pressure. Dr. Thomas Samuelson, a glaucoma specialist with Minnesota Eye Consultants, was the study's medical monitor.

Dr. James Salz, a spokesman for the American Academy of Ophthalmology and clinical professor of ophthalmology at the University of Southern California, said that the future of the use of the devices depends on whether the "success rate is high and complication rate is low."

In many patients with glaucoma, the fluid inside the eye creates pressure that damages the optic nerve. Most glaucoma patients are able to control their eye pressure with eye drops and don't need surgery. But the drops can cost as much as $100 a month and require patients to use them for decades, Salz said.

Those aren't the only drawbacks to eye drops, another expert noted.

Many patients don't like the drops and fail to use them on a regular basis, said Dr. Alfred Sommer, a professor of ophthalmology at Johns Hopkins University in Baltimore and dean emeritus of Hopkins' Bloomberg School of Public Health. Another option is surgery to allow better draining of the fluid in the eye.

In June, the U.S. Food and Drug Administration approved a "mini-stent" known as the iStent to treat glaucoma patients who also have a cataract. The stent, a tiny tube of titanium, is designed to allow better draining of eye fluid.

In a new study, scheduled to be presented Tuesday at the annual meeting of the American Academy of Ophthalmology in Chicago, researchers tested the Hydrus stent, another kind of titanium stent, on 69 patients with mild to moderate glaucoma.

Forty of the patients also had cataracts and underwent the stent procedure during cataract surgery, which often helps reduce eye pressure on its own. After six months, 85 percent of them saw their eye pressure improve to the point that they didn't need to use eye drops. The number was 70 percent among those who didn't require cataract surgery.

The results persisted at the one-year time point.

As for cost, the stents may not cost more than a few hundred dollars, Salz said. Side effects can include scarring, he noted. However, the new study reports no complications.

In a news release, the American Academy of Ophthalmology noted that the iStent has been approved and several other kinds of stents are under development. "Despite encouraging initial results, it will be several years before the long-term safety, efficacy and durability of this treatment approach can be fully confirmed," the academy cautioned.

Sommer questioned whether the lowered pressure level is significant enough in the study patients who received the stent. The findings also don't make it clear what happened to the peripheral vision of the patients, which can be disrupted by glaucoma, he said.

For his part, Salz said it's not clear if the stents will ultimately be used in any patients who don't have cataracts. Still, "if the long-term success looks good, they may consider putting them in eyes that don't have cataracts."

Neither Sommer nor Salz was involved with the research.

Because this study was presented at a medical meeting, the data and conclusions should be viewed as preliminary until published in a peer-reviewed journal.

More information

For more about glaucoma, visit the U.S. National Library of Medicine.