Evaluation of the Impact of the XEN® Implant on Endothelial Cell Density, 3 Years After Surgery

Glaucoma is a blinding optic neuropathy affecting 80 million people worldwide, with primary open-angle glaucoma being the most common etiology. Today, the therapeutic arsenal includes drug-based hypotonizing treatments, lasers and surgery. In France, the most common surgical techniques for glaucoma are trabeculectomy and deep non-perforating sclerectomy (SPNP). These are two filtering techniques designed to lower intraocular pressure (IOP) by creating an escape route for aqueous humor from the anterior chamber (AC) of the eye into the subconjunctival space, creating a filtering bubble (FB). They can be performed alone, or at the same time as cataract surgery. The short-term complications encountered with these techniques are early hypotony and its attendant complications (choroidal detachment, hypotonic maculopathy, haemorrhages, etc.), the most frequent cause of which is conjunctival leakage of the bubble. In the medium term, tension rises with a deep anterior chamber are evidence of an over-tight scleral flap, which may require suture lysis. Finally, problems of excessive conjunctivotenone scarring affect 25% to 30% of patients, and are responsible for the majority of late tension increases. In the longer term, the most frequent complication is cataract. The rarest but most serious complication is infection of the BF, which occurs more frequently when the walls of the BF are ischemic or perforated. It can be complicated by endophthalmitis, which can lead to irreversible loss of visual acuity.

A new minimally invasive treatment option has been developed to limit intra- and post-operative complications. This new technique is based on an ab interno approach, with implantation through the anterior chamber of a 6mm-long, 45µm-lumen collagen tube called XEN®. There is no need to dissect the conjunctivotenon planes, as is the case with traditional surgery.

The geometry of the XEN® implant has been designed to prevent major hypotonia. This new technique avoids the complications associated with conjunctival dissection, while being faster and offering a standardized surgical technique. ). Today, XEN® implant placement is used in simple surgery or combined with cataract surgery for open-angle glaucoma, incipient to moderate, associated or not with a cataract, progressive and unbalanced under local hypotonizing treatment.

Since June 2017, surgeons have been able to use the XEN® technique in the GHPSJ ophthalmology department.

To date, no study has assessed endothelial cell loss more than 2 years after this surgery. Indeed, the presence of an anterior chamber device of any type may be associated with endothelial cell loss that increases over time, well after the operation, and may require removal of the device several years after the operation. One study showed that the microinvasive ab interno Alcon Cypass® device (a device similar to XEN®) caused significant endothelial cell loss 2 years after device implantation, and was unacceptable compared with conventional glaucoma surgery. The damage was proportional to the surface area of the implant in the anterior chamber, and led to the immediate withdrawal of the device from the market.

Recent studies have examined peripheral endothelial cell loss with other drainage systems. They show a significant reduction in peripheral endothelial cell density in relation to the implant placed in the anterior chamber. Intracameral devices appear to have an impact on endothelial integrity. To date, no study has assessed long-term central and peripheral endothelial cell density after XEN® placement.

At the visit more than 3 years after XEN® implantation, intraocular pressure (IOP) is measured with a Goldmann applanation tonometer, pachymetry with a NIDEK automatic refractometer and central and peripheral endothelial cell density with a NIDEK specular microscope. Peripheral corneal endothelial cell density is measured on the various ocular quadrants. The same measurements are taken on the controlateral eye. Patients undergoing surgery on both eyes receive the same measurements for each eye.