COMMENTARY

Supraciliary Stents as an Alternative to Filtering Surgery in Open-Angle Glaucoma

Shuchi B. Patel, MD

Disclosures

July 21, 2015

Viewpoint

Avoiding a bleb-forming procedure has been the goal of most new devices being developed for glaucoma. Surgeons would like to avoid not only intraoperative complications of filtering surgery but also postoperative complications and failures.

Therefore, significant attention has been turned to the suprachoroidal space. It was previously thought that only a small percentage of outflow was through the uveoscleral pathway into the suprachoroidal space, with the majority of outflow being through the trabecular meshwork. Recent studies suggest that the uveoscleral pathway may play a larger role than imagined.[1] The effective use of prostaglandin analogs to increase uveoscleral outflow and decrease IOP, as well as the potential for hypotony in the presence of a cyclodialysis cleft, prove that the suprachoroidal space has significant outflow potential. Therefore, a controlled "cyclodialysis cleft" could reduce IOP without a bleb-forming procedure.

The CyPass Micro-Stent is commercially available in many European countries and has potential to be this controlled solution. It is a fenestrated micro-stent that is made from a biocompatible polyimide material. The total external diameter is 510 µ, and it is 6.35 mm in length.

Implantation is through a standard clear corneal incision. A gonioscopy lens is used to visualize the angle as the device is implanted between the ciliary body and sclera into the supraciliary space with the assistance of a stiff guidewire. After implantation, the device assumes the curvature of the globe and is kept in place by retention rings at the proximal end. As with any new procedure, there will be a learning curve, but given that many ophthalmic surgeons are becoming more familiar and comfortable with angle-based surgery, implantation of this device is within the realm of procedures for general ophthalmologists. They also may find this implant to be superior to gold-standard filtering surgery with low complication rates and shorter intraoperative times.

The 1-year results of this study show that the mean IOP was reduced from 24.5 mm Hg to 16.4 mm Hg. Although the resultant IOP was not as low as the range seen with standard filtering surgery (10-13 mm Hg), more than 80% of patients in this study accomplished a reduction in IOP that was sufficient to obviate the need for more invasive surgery. In clinical practice, not all patients may need IOPs as low as 10 mm Hg. By performing a minimally invasive glaucoma procedure, these patients could potentially avoid complications seen with the gold standard bleb-forming procedures.

Furthermore, data[2] presented at the American Glaucoma Society meeting in 2015 suggested that, with devices such as the iStent® (Glaukos; Laguna Hills, California), implantation of more than one device reduces pressure even further than one device alone. The same may hold true for the CyPass, where implantation of two devices may produce a decrease in IOP comparable to that seen with gold standard filtering surgery. Also, given that this procedure does not violate the conjunctiva, implantation of this device does not preclude future bleb-forming procedures, should they become needed.

The data from this current study are similar to previously reported data,[3] which suggested that the CyPass is a relatively safe and effective treatment for open-angle glaucoma. According to the previously reported data,[3] 1 year after surgery with the CyPass alone, IOP was reduced by 26% and glaucoma medication use was reduced by a third in those who had uncontrolled glaucoma prior to surgery. For those who already had their glaucoma under medical control, implantation of the CyPass resulted in a 39% average reduction in glaucoma medication use.

Recently published data[4] from the CyCLE (CyPass Clinical Experience) study demonstrated that when the CyPass was implanted in conjunction with cataract surgery, IOP was reduced by 35%, and medication use decreased by an average of 49% 1 year after surgery. For patients whose IOP was already under control prior to surgery, implantation of the CyPass at the time of cataract surgery reduced medication use by 75%.

Another study[5] demonstrated consistent results with an IOP reduction of 37% and more than a 50% reduction in the use of glaucoma medications at 6 months. Patients with controlled IOP had a 71.4% reduction in glaucoma medications.

Data from the current and previous studies of CyPass seem to show that, even as a stand-alone procedure, the results are promising.

Limitations of this study from Garcia-Feijoo and colleagues are that it was single-armed with no control group. Also, if this procedure is to be recommended in conjunction with cataract surgery, a study comparing cataract extraction alone with cataract extraction plus CyPass should be conducted. Furthermore, this study has a short follow-up. Failure rates due to scarring may pose a significant challenge in the long term. Data from the 24-month follow-up of the DUETTE clinical study will be useful in determining long-term success. In addition, the study lacked a protocol for determining reinitiation of medication. Therefore, true IOP reduction of the device alone cannot be determined.

CyPass is not currently available for commercial use in the United States but may be approved in 2018. Having this device as an additional option will expand the horizons of glaucoma surgery.

Abstract

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