Study Comparing the Kinetics of Endothelial Cell Loss Associated With the XEN® Implant Versus Traditional Filtering Surgery for Glaucoma

Glaucoma

endothelial cell loss, XEN® implant, filtering surgery

Glaucoma is a blinding optic neuropathy that affects 60 million people worldwide. Of all the types of existing glaucoma, primary open-angle glaucoma is the most common etiology. The therapeutic arsenal today includes drug lowering treatments, lasers and surgery. The most frequent glaucoma surgeries are, in France, trabeculectomy and non-perforating deep sclerectomy (NPDS). These are two filtering surgeries whose principle is to lower the intra ocular pressure (IOP) by creating an evacuation path of the aqueous humor from the anterior chamber (AC) of the eye to the space subconjunctival creating a filtration bubble (FB). These two procedures are currently considered the gold standard. They can be performed alone or at the same time as cataract surgery. The short-term complications encountered with these techniques are early hypotonia and its attendant complications (choroidal detachment, hypotonic maculopathy, hemorrhages, etc.), the most common cause of which is conjunctival leakage from the bubble. In the medium term, increases in blood pressure with deep AC testify to a scleral flap that is too tight which may require suture lysis. Finally, the problems of excessive conjunctival-Tenon healing concern 25 to 30% of those operated on and are responsible for the majority of late blood pressure increases. In the longer term, the most common complication is cataracts; the rarest, but most serious complication is infection of BF, which occurs more readily when the walls of the FB are ischemic or even perforated. It can be complicated by an extremely serious endophthalmitis. A new minimally invasive therapeutic option has been developed limiting per- and post-operative complications. Unlike traditional techniques which present an ab externo approach, the ab interno approach of the new technique proposed consists of the implantation of a tube of collagen 6 mm in length and 45 µm of light called Xen® through the AC .

This surgery can be performed alone or at the same time as cataract surgery. The geometry of the Xen® implant has been studied to help prevent major hypotonia. This new technique would also prevent complications related to conjunctival dissection, while being faster. The placement of a Xen® implant is now used in simple surgery or combined with cataract surgery for open-angle glaucomas, beginners to moderate, associated or not with cataract, progressive and unbalanced under local hypotonizing treatment. Since June 2017, the Xen® technique has been part of the routine in the ophthalmology department of the Paris Saint-Joseph Hospital Group (GhPSJ). The choice of technique (filtering surgery or XEN®) is left to the discretion of the surgeon. To date, no study has yet compared the efficacy and safety of this new technique compared to non-perforating deep sclerectomy: the gold standard. However, the presence of any type of anterior chamber device may be associated with endothelial cell loss even when the device is not in direct contact with the cornea. Endothelial cell loss increases over time well after the operative procedure and sometimes requires removal of the device years later. It can induce non-reversible corneal edema when the device is stopped and involve a corneal transplant. Recently, a study showed that the micro-invasive device ab interno Alcon Cypass® (device similar to XEN®) caused an endothelial cell loss that was not significant initially but significant thereafter (48 months) and not acceptable compared to conventional surgery. glaucoma. The damage was proportional to the area of the implant in the anterior chamber and led to the immediate withdrawal of the device from the market. In view of these results and the absence to date of an equivalent study for XEN®, we proposed to conduct this study in order to assess the possible cell loss compared to NPDS.

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