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One-year after implantation of the Cypass Micro-Stent, study results demonstrate a reduction in IOP and glaucoma medications, as well as a complete lack of sight-threatening adverse events. The implant is placed into the supraciliary space to facilitate suprachoroidal aqueous outflow in glaucoma patients.
Take-home message: One-year after implantation of the Cypass Micro-Stent, study results demonstrate a reduction in IOP and glaucoma medications, as well as a complete lack of sight-threatening adverse events. The implant is placed into the supraciliary space to facilitate suprachoroidal aqueous outflow in glaucoma patients.
By Dr Magda Rau
Topical medication is the primary treatment option for open angle glaucoma. However, such an approach requires lifelong dependence on self-administered therapy.
Almost 50% of glaucoma patients require multiple intraocular pressure (IOP)-lowering medications for adequate pressure control and this polypharmacy often presents numerous challenges for patients.1,2 Varied dosing regimens and compound side effects can decrease patient compliance3,4 and additionally, chronic ocular surface problems are more common when multiple topical medications are prescribed.5 In some cases, the maximal possible medication is not capable of effective pressure reduction, even with good compliance.
The most common surgical option for lowering IOP is a guarded full- or partial-thickness filtration procedure such as trabeculectomy. However, conducting such a procedure introduces the risks of hypotony, hyphema, bleb leakage, bleb infection, and endophthalmitis. Indeed, complications may be experienced in more than 35% of filtration cases.6 As a result, filtering surgery is often reserved only for severe cases of progressive glaucoma.7
Experimental evidence suggests that increasing non-trabecular, uveoscleral outflow is a desirable approach to lowering IOP in patients with glaucoma. There is a negative pressure gradient between the suprachoroidal space and the anterior chamber that may provide a driving force for such aqueous outflow.8 In some areas the pressure difference can exceed 3–4 mmHg, with a gradient that increases along the posterior aspect of the suprachoroidal space. Clinical experience demonstrates that traumatic or iatrogenic cyclodialysis results in significant IOP reduction by creating additional non-trabecular outflow through the uveoscleral route.9,10
The CyPass Micro-Stent (Transcend Medical, Inc., Menlo Park, CA, USA.) is a novel device designed to lower IOP. It is constructed from a biocompatible, non-degradable polyimide material. It measures 6.2 mm in length, has an inner diameter of 0.3 mm, and features proximal retention rings that help to stabilise its position in the supraciliary space. The device is implanted through a clear corneal incision (2.8-1.5 mm), into the supraciliary space to facilitate suprachoroidal aqueous outflow. The procedure is ab interno, minimally invasive, spares the conjunctiva and the sclera and is less traumatic than full thickness penetration procedures.
From May 2009 to July 2011 a surgeon at the Augenklinik Cham, Germany, implanted the Cypass Micro-Stent followed in 33 eyes of 33 patients. Twenty-four of these implantations were combined with cataract surgery and 9 were conducted as a stand-alone procedure. Patients underwent a 12-month follow-up.11,12,13
Inclusion criteria for the study were: diagnosis of open-angle glaucoma in the study eye, with Schaffer grade 3 or 4, best corrected visual acuity (BCVA) better than 0.3 at the preoperative visit; a mean medicated or unmedicated IOP in the study eye of ≥21 mmHg; and ≤31 mmHg or 2-3 medications. Exclusion criteria were: diagnosis of acute angle closure, narrow angle, uveitic or neovascular glaucoma in the study eye, as well as diagnosis of normal tension glaucoma in the study eye.
Length of follow-up was 1 year, with visits at 1 day, 1 week, 1 month, 3 months, 6 months and 12 months post-operatively. All patients adhered to follow-up and attended all visits.
The mean IOP measurement was 22.3 mmHg in the combination glaucoma-cataract surgery group at baseline. At 12 months, mean IOP readings had reduced to 15 mmHg.
Mean medication use was also reduced, from 1.8 at baseline to 0.8 at 12 months (17 patients).
For eyes undergoing implantation of the stent as a standalone procedure, mean baseline IOP was 26 mmHg with a mean of 1.3 medications. Five eyes were seen at 12 months and had a mean IOP of 13.2 mmHg. In addition, these patients were taking an average of 0.8 medications.
No sight-threatening adverse events or cases of inflammation occurred during the study. Minor intraoperative bleeding was observed in three eyes without development of hyphaema, and two eyes developed transient hypotony that resolved within one month.
Early migration of the implant occurred in one patient, and was addressed with a repositioning procedure. The patient recovered without any clinical sequelae and had an IOP of 13 mmHg at 24 months.
The overall reduction in IOP and glaucoma medications, combined with a complete lack of sight-threatening adverse events in this study demonstrate that implantation of the CyPass Micro-Stent, either in combination with cataract surgery or as a standalone procedure, is indeed an effective and safe microinvasive treatment for patients with open angle glaucoma.
Dr Magda Rau
Dr Magda Rau works at the Augenklinik Cham, Germany.
Dr Rau works for Transcend Medical as an investigator and consultant and has received research funding from the company.