Anterior segment OCT for imaging PAUL® glaucoma implant patch grafts: a useful method for follow-up and risk management.

Aim: To evaluate a useful, non-contact method for the follow-up of pericardium patch graft changes in patients undergoing PAUL^® Glaucoma Implant (PGI) surgery using high-resolution anterior segment optical coherence tomography (OCT) to predict tube erosions.

Methods: Prospective analysis over six months of tube pericardium patch graft thickness of PGI surgical cases at the University Eye Hospital Bonn, Germany, from November 2021 to August 2022. In all eyes, Tutopatch^® (RTI Surgical, United States) pericardium was used to cover the implant intra-operatively. Anterior segment OCT (AS-OCT, Heidelberg ANTERION^® Swept-Source-OCT) examinations were performed following a standardized protocol to measure quantitative and qualitative aspects of the patch grafts before surgery, and at three and six months after surgery.

Results: Twenty-six eyes of 26 patients were included. Thickness of the patch material was 1188 µm (IQR 415 µm) directly after implantation and decreased over time to 1068 µm (IQR 478 µm) at 3 months and 846 µm (IQR 677 µm) at 6 months. No significant differences between groups were shown concerning gender (p = 0.128), ethnicity (p = 1.000), age (p = 0.741), glaucoma type (p = 0.173), other concurrent diseases (p = 0.302), former glaucoma surgeries (p = 1.000) and the quadrant of implantation (p = 0.555). Five eyes developed implant exposure. When comparing eyes with and without tube exposure, no significant differences were shown in average patch thickness above the tube directly after implantation (p = 0.476). However, significant differences in average thickness were observed at 3 months (p = 0.013) and 6 months (p = 0.005).

Conclusions: Pericardial patch grafts tend to thin over time which can be assessed by AS-OCT, the latter proving to be a useful method to follow-up patients who undergo patch graft implantation during PGI surgery. This investigation could potentially help identify patients at risk of tube exposure which in turn could lead to modification of patient management. It could also possibly be used in future studies to find more suitable patch materials.