Advances in Glaucoma Surgery

In the lineup of available treatment options for glaucoma, minimally invasive procedures that can reduce intraocular pressure (IOP) and the risk of vision loss are filling a need.

Filtration surgeries such as trabeculectomy or placement of a glaucoma drainage device have their drawbacks. “These are associated with a significant decrease in IOP, but also have high adverse event rates,” says Malik Y. Kahook, MD, Chief of the Glaucoma Service and a Professor of Ophthalmology at the University of Colorado Anshutz Medical Campus in Aurora, Colorado.

Such drawbacks have led surgeons and inventors on a quest to find safer ways to bridge the divide between laser and filtration surgeries. That gap is now being filled by minimally invasive glaucoma surgery (MIGS)—the latest advance in glaucoma treatment. According to Dr. Kahook, their major advantage is that they allow for a more regulated outflow of fluid from one area to another. “Traditional surgeries don’t offer this degree of regulation, so there can be dramatic fluctuations in pressure,” he says.

The newer products are small shunts or stents that carry fluid from one compartment of the eye to another to decrease IOP. The best known of these is the iSTENT® from Glaukos, a miniature titanium device that shunts fluid from the inside of the eye to the drainage system, bypassing the obstruction to fluid flow. Precision-made with small lumens, the iSTENT has an excellent safety profile, but a less robust effect on IOP.

“Available MIGS devices fit in multiple categories that depend on where they shunt fluid from,” says Dr. Kahook. The first category shunts it from the anterior chamber into Schlemm’s canal; the second does so from the inside of the eye to the suprachoroidal space; and the third, from the eye into the sub-Tenon’s space. Major players in the MIGS market include Glaukos, Ivantis, Transcend Medical, and AqueSys. Their products differ in size and construction, but all decrease IOP. “They just do it in slightly different ways,” says Dr. Kahook.

They also work well in conjunction with cataract surgery. MIGS are implanted in a way that doesn’t damage the tissue around them. Used with cataract surgery, another minimally invasive procedure, the surgery quickly gives patients improved vision along with decreased IOP. When traditional, more invasive glaucoma surgeries are performed with cataract surgery, they delay the recovery of vision and have higher rates of adverse events.

Today, glaucoma is the leading cause of irreversible blindness in adults. An estimated four million people in the U.S. and over 60 million worldwide are afflicted with the disease, and those numbers are expected to grow to nearly six million in the U.S. and to over 70 million worldwide by the year 2015.

Several promising MIGS devices are in development. Without closing the door on traditional surgical techniques, they promise to revolutionize glaucoma surgery and provide safer treatment alternatives.

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