Ab-interno trabeculectomy with novel ablative device encouraging based on case series outcomes

October 15, 2008

Outcomes data for ab-interno trabeculectomy with a novel ablative device (Trabectome, NeoMedix) to ablate thermally the trabecular meshwork consist of case series. So far, this procedure has been associated with favorable IOP lowering, but a direct comparison with standard trabeculectomy is needed, according to one glaucoma specialist.

Key Points

Boston-Further research is needed to delineate what role ab-interno trabeculectomy with a novel ablative device (Trabectome, NeoMedix) will have in the surgical management of glaucoma. Based on experience to date, however, it is a promising contender in the search to find a viable alternative to trabeculectomy, said Douglas J. Rhee, MD.

"[Surgery with this device] appears to offer good IOP control," said Dr. Rhee, assistant professor of ophthalmology, Harvard Medical School, Boston. "However, available data are from consecutive case series. While such information has merit for initial evaluations, comparisons with trabeculectomy are necessary if this surgery is being considered as its possible replacement."

Site of resistance modified

The patient lies with his or her head tilted away from the surgeon, and the pupil is not dilated unless combined cataract surgery is being performed. The procedure is performed one-handed.

"The second hand holds the gonioscopic lens, which is necessary for visualization," said Dr. Rhee, also affiliated with the Massachusetts Eye and Ear Infirmary.

After creating a paracentesis and filling the eye with acetylcholine chloride intraocular solution (Miochol-E, Novartis), a 1.6-mm keratome is used to create a clear corneal, near-limbal incision.

The device is introduced under direct visualization and advanced under gonioscopic control. The footplate engages and punctures the trabecular meshwork. The footplate of the tip is placed into Schlemm's canal. Thermal cautery is used to remove a portion of the trabecular meshwork, directly exposing Schlemm's canal and the nasal collecting channels to the anterior chamber.

"This is the one time surgeons are glad to see blood in the eye because it is reflux from Schlemm's canal and signifies that an open connection has been established between the anterior chamber and the aqueous veins," Dr. Rhee said. "The corneal incision created with the [device] is self-sealing."

Initial clinical data for this procedure were published in 2005 in Ophthalmology by Minckler et al., who reported an approximate 38% lowering of IOP after 6 months in a group of about 25 eyes. The next year, data were reported from a cohort of 101 eyes with follow-up ranging up to 30 months. Success, defined by IOP <21 mm Hg regardless of medications, was achieved by 84% of eyes.

In 2008, results were reported from 679 eyes and showed IOP control was adequate enough so that only 8% of the cohort needed subsequent glaucoma surgery performed.

"The biggest advantage of this procedure is that if it fails, trabeculectomy still can be performed because a quadrant of conjunctiva has not been wasted," Dr. Rhee said. "I consider the procedure an option for eyes [in which] laser trabeculoplasty [has failed].

"At least for now, glaucoma surgeons will continue to depend on trabeculectomy and tube shunts," Dr. Rhee concluded. "Future research such as a prospective clinical trial comparing [the device] with trabeculectomy would help to clarify more decisively the place of this promising new procedure within our armamentarium."

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