Changes in Corneal Endothelial Cell Density After Transscleral ab Interno Glaucoma Gel Stent Implantation

STUDY OBJECTIVE Corneal endothelial cell loss is a known sequela of glaucoma tube shunt implantation. Big tube shunts show a decrease of endothelial cell count postoperatively (-11.5% after Ahmed glaucoma valves and -12.4% after Molteno shunt 2 years postoperatively). The objective of this study is to evaluate the change of endothelial cell count after XEN45 in patients with or without cataract operation.

PATIENT POPULATION In 140 open angle eyes central endothelial cell counts were recorded preoperatively, before the XEN45 implantation was performed in Dept. Ophthalmology at Paracelsus Medical University Salzburg. XEN45s were already performed in the year 2013-2017 (so up to 5 years) in open angle glaucoma eyes in combination with or without cataract operation. In these eyes central endothelial cell count and central corneal thickness was measured preoperatively and documented in patients records.

STUDY DESIGN A prospective, observational, monocentric trial to evaluate the course of endothelial cell density after the XEN implant. The study will take place in the Dept. Ophthalmology at Paracelsus Medical University Salzburg/SALK.

Up to 140 consecutive patients with preoperatively recorded endothelial cell counts will be summoned to a consecutive endothelial cell count record and measurement of central corneal thickness postoperatively. Informed consents will be obtained from patients, who are interested in participating in the study.

Patients will be assessed for endothelial cell density and the position of the XEN45 measured by anterior segment optical coherence tomography. The distance of the XEN45 to cornea, the angle of the tube, and the tube length in the anterior chamber will be recorded with anterior segment optical coherence tomography. Endothelial cell density will be measured on 3 positions: central, superior-nasal (location of XEN45 implantation), infero-temporal (far away for the XEN45 implant).

OUTCOME PARAMETERS The primary endpoint is the change of central endothelial cell density compared to preoperative data.

Secondary objectives are the differences of supero-nasal and infero-temporal endothelial cell density compared to the central endothelial cell density, and pachymetry compared to preoperative data.

EXAMINATION SCHEDULE Subjects will undergo study visits at the following times: preoperative data (2013-2017) out of patient records, postoperative visit in the year 2018-2020 (1-7 years post XEN45 implantation).

CLINICAL PARAMETERS

The following clinical assessments will be performed at the postoperative examination:

• Endothelial cell count on different locations of the study eye
• Central corneal thickness
• Anterior segment optical coherence tomography (to determine the position of the XEN45)
• Slit lamp examination of the cornea, anterior segment including gonioscopy (to determine the position of the XEN45), and dilated fundus examination
• Best corrected visual acuity
• Measurement of IOP
• Number and frequency of ocular (glaucoma) medications
• Ocular symptoms and assessment of complications (especially symptoms, which may be a hint for loss of endothelial cell count)
• Secondary surgical procedures (if applicable including needlings, lasers, cataract operation, bleb revisions, keratoplasty, secondary IOP lowering procedures, other operations)

Inclusion criteria

• Open Angle Glaucoma
• History past XEN45 implantation with or without combined cataract procedure
• Available preoperative endothelial cell count data not older than 1 year before XEN operation without any operation between the day of data record and XEN45 operation.
• Age 18 years or older and of legal age of consent
• Signed written informed consent
• Availability, willingness, and sufficient cognitive awareness to comply with examination procedures

Exclusion criteria

• Patients with secondary IOP lowering procedures (excluding SLT, needlings, bleb revisions, YAG lasers, Argon lasers) after XEN implantation will be excluded from analysis, because the secondary IOP lowering procedures may influence endothelial cell count itself. Cataract operations without complications are no exclusion criteria, but have to be recorded.