Comparison of Keratometric Change After Xen Gel Stent Implantation, Trabeculectomy, and Tube Shunts

Following glaucoma surgery, patients often experience decreased visual acuity (VA) which can partly be explained by induced changes to the optical properties of the cornea. Corneal astigmatism can be assessed using corneal topography, a non-invasive tool which provides an accurate estimate of corneal curvature in all meridians. Obtained keratometric measures (termed K values) can allow clinicians to quantify the amount of astigmatism before and after surgical intervention.

Multiple studies have been previously published to evaluate induced postoperative astigmatism after trabeculectomy. However, only two studies have characterized the impact of GDDs on keratometric values. To the best of our knowledge, no study has yet attempted to quantify the amount of astigmatism induced by the XEN Gel Stent.

Assessing the impact of the XEN implant on corneal astigmatism is important to better characterize the expected course of postoperative visual rehabilitation, the impact of novel glaucoma devices on corneal properties and the predictability of refractive outcomes after XEN implantation. Compared to traditional filtering surgery, the XEN Gel Stent is inserted without opening the conjunctiva and is implanted further from the corneal limbus (5 mm). These factors may allow for a reduced amount of surgically induced corneal astigmatism.

We hypothesize that the XEN Gel Stent implantation induces less corneal astigmatism compared to traditional filtering surgery, such as the trabeculectomy and GDDs (BGI or AGV).

The main goal of this prospective interventional comparative study is to assess the severity of postoperative corneal astigmatism induced by implantation of the XEN Gel Stent compared to that induced by traditional filtering surgery (trabeculectomy and GDDs).