Glaucoma
Drainage device use continues to crowd out blebs

Glaucoma drainage valves

Surgeons report that they find most glaucoma drainage devices have improved outcomes over blebs while lacking some of the complications blebs can produce

Eye with thin, avascular leaking blebs.
Source: Michael Berlin, M.D.

The use of glaucoma drainage devices has grown among leading surgeons in recent years as the indications for their use have continued to grow among patients with serious progression. The use of the devices could further expand as outcomes improve over traditional trabeculectomy and improved drainage equipment becomes available.

Douglas J. Rhee, M.D., assistant professor, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, is one surgeon who reports that all of his patients who received drainage devices in recent years would previously have undergone a trabeculectomy.
“So the number of trabeculectomies I’ve done has dropped off a lot,” Dr. Rhee said.
Dr. Rhee has used all of the Food and Drug Administration-approved drainage devices including the ExPress Mini Glaucoma Shunt (Optonol, Kansas City, Kan.), Trabectome (Neomedix, Tustin, Calif.), Molteno (IOP, Costa Mesa, Calif.), and canaloplasty (iScience, Menlo Park, Calif.).

Canaloplasty headlines

The newest device for Dr. Rhee and one that has drawn considerable excitement in recent years is canaloplasty. However, surgeons now report mixed reviews of the procedure. One common complaint of the procedure and also found by Dr. Rhee is that canaloplasty, which aims to improve drainage through the canal of Schlemm, is a “surgically and technically challenging.”
“There is a certain period of learning about the procedure that has to happen first,” Dr. Rhee said.
Francis W. Price Jr., M.D., Price Vision Group, Indianapolis, and president of the board, Corneal Research Foundation of America, Indianapolis, reported that he had little trouble finding Schlemm’s canal because he performs many non-penetrating porocedures. However, he described the procedure as a lot of effort for patient pressure outcomes that were “not all that great.” He primarily relies on the nonpenetrating AquaFlow collagen glaucoma drainage device (STAAR, Monrovia, Calif.).
Conversely, Louis B. Cantor, M.D., Jay C. and Lucile L. Kahn Professor of Glaucoma Research and Education and vice chairman, Education, Department of Ophthalmology, Indiana University School of Medicine, Indianapolis, reported canaloplasty provided favorable results with good, blebless IOP control in the majority of his patients who have undergone it.
E. Randy Craven, M.D., Littleton, Colo., suggested that surgeons considering adding canaloplasty to their surgical armamentarium might have better results if they become more familiar with Schlemm’s canal and the trabecular meshwork.
One way of improving familiarity with these structures is through increased use of gonioscopy, which allows a view of the angle and its critical landmarks. Use of the older gonioscopy instead of performing an ultrasound biomicroscopy or OCT (Ophthalmic Technologies, Toronto) can identify narrow angles while also helping to prepare surgeons for canaloplasty.
“You need to [perform gonioscopy] if you are going to operate in the area because you need to know what you’re looking for,” Dr. Craven said. “So surgically, doctors considering these newer procedures need to start re-examining the angle and spend more time thinking about that.”
Other mainstay glaucoma drainage devices include the Baerveldt implant (Abbott Medical Optics, Santa Ana, Calif.) favored by Dr. Cantor. The three-year results of the Tube versus Trabeculectomy Study, released in 2009, suggested at least an equivalent success rate of the devices compared to trabeculectomy, said Dr. Cantor, while the devices also lowered the risk for some bleb-associated complications. He noted that tube shunts have their own potential complications, including extrusion, ocular motility disturbances and corneal decompensation.

Devices draw fire

Not all glaucoma drainage devices are created equal, according to some surgeons.
For instance, Dr. Rhee said his surgical experience with the Molteno device has been “a great disappointment,” due to problems with efficacy and serious side effects. In addition, he has found the device more technically difficult to implant than either the Baerveldt implant or Ahmed valve (New World Medical, Rancho Cucamonga, Calif.), for instance.
Similarly, Dr. Craven reported that he was “personally disappointed” with the overall performance of the Solx Gold Micro-Shunt (Occulogix, Mississauga, Ontario). He found persistent problems with pressure control, as well as chronic inflammation in patients in whom he implanted the device.

Coming devices may offer improvements

Among the emerging glaucoma drainage devices is at least one related to canaloplasty. Dr. Cantor has participated in the trials of the iStent (Glaukos, Laguna Hills, Calif.), which focuses on segmental parts of Schlemm’s canal.
“This microstent offers the possibility of improving outflow via the canal of Schlemm, again without a filtering bleb and the associated potential risks of a bleb,” Dr. Cantor said.
Dr. Craven said the emerging smaller stents, such as the iStent, offer improvements in glaucoma drainage because they are less disruptive to the eye and avoid the use of a filtering bleb. In Dr. Craven’s experience, patients who receive the snorkel-shaped Glaukos device have no inflammation or other problems associated with it. Yet, recipients of the small stent are able to maintain consistent pressures in the mid-teens for at least three years while using few medications, according to the latest research.
“So we’re moving in the right direction with glaucoma surgery,” Dr. Craven said. “We’re getting safer, more controlled outcomes from surgery.”
Significant advantages could come with the emergence of suprachoroidal drainage devices, including at least one such device that goes into the suprachoroidal space without having to cut through the sclera. Such an approach could avoid inflammation problems that Dr. Craven saw with the Solx shunt.

Editors’ note: Drs. Rhee and Price have no financial interests related to their comments. Dr. Craven has been an investigator on all available devices. Dr. Cantor has financial interests with Abbott Medical Optics (Santa Ana, Calif.) and Glaukos (Laguna, Calif.).

Contact information

Cantor: 317-274-8485, lcantor@iupui.edu
Craven: 303-798-7100, ercraven@yahoo.com
Price: 317-814-2823, fprice@pricevisiongroup.net
Rhee: 617-573-3670, Douglas_rhee@MEEI.Harvard.edu