The iStent trabecular micro-bypass stent is an investigational device in clinical trials in the United States for the treatment of glaucoma in patients undergoing cataract surgery. It is delivered ab interno through a clear corneal incision, advanced through the trabecular meshwork and implanted into Schlemm canal where it creates a pathway for aqueous humor to drain directly from the anterior chamber into Schlemm canal. The procedure avoids any manipulation of the iris, conjunctiva, or sclera, and thus preserves all other surgical and medical options. Stent implantation requires the device, its applicator, and a manual gonioprism. Other recently developed techniques for surgery on the angle require high-technology instrumentation.
An ongoing clinical trial in Europe has interim 18-month data from 41 of the 58 patients. Mean intraocular pressure (IOP) at baseline was 21.5 mm Hg (N = 58) and was significantly reduced from baseline at each study visit (P < 0.001). At 18 months, mean IOP was 16.7 mm Hg (n = 41; P < 0.001), and the mean number of antiglaucoma medications was significantly reduced from 1.6 at baseline (N = 58) to 0.4 at 18 months (n = 41; P < 0.001). The iStent device is safe for experienced cataract surgeons. It uses the corneal incision used for cataract surgery, is not associated with the significant complications common to penetrating procedures, provides sustained and significantly reduced IOP over an 18-month period, and reduces the need for glaucoma medications. The iStent implant may deliver therapeutic benefits that compare favorably with conventional medical and surgical treatments for glaucoma.