Bleb Morphology Using Anterior-Segment Optical Coherence Tomography after Ahmed Glaucoma Valve Surgery with Tenon Capsule Resection

Abstract

Objectives. To evaluate the internal morphology of blebs using anterior-segment optical coherence tomography (AS-OCT) and the surgical outcomes of Ahmed glaucoma valve (AGV) surgery with Tenon capsule resection compared to conventional AGV surgery in patients with refractory glaucoma. Patients and Methods. This randomised prospective study included 30 eyes from 30 patients (age range: 42–55 y) with refractory glaucoma from March 2018 to February 2020. The study included two groups: AGV with the Tenon capsule resection group (n = 15) and the conventional AGV surgery group (n = 15). Follow-up continued until 6 months after surgery. The primary outcome was intraocular pressure (IOP) and its association with the number of postoperative glaucoma medications, best corrected visual acuity, visual field, and postoperative complications. The internal morphology of the blebs in both groups was evaluated at 1-day, 1-week, 1-month, 3-month, and 6-month follow-up using AS-OCT in terms of the consequent changes in bleb wall thickness, bleb wall reflectivity, and bleb cavity morphology throughout the 6-month follow-up period. Results. A significant reduction in IOP was found in both groups, with a greater reduction in group I, where the mean IOP decreased from 32.73 ± 2.12 mmHg in the preoperative period to 13.33 ± 1.59 mmHg after 6 months, whereas in group II, the mean IOP decreased from 33.2 ± 2.21 mmHg in the preoperative period to 14.27 ± 1.44 mmHg after 6 months ( $p$ value <0.05). The difference between the 2 groups in terms of the decrease in IOP was insignificant except at 1 and 3 months, where there was a significant difference ( $p$ value = 0.016 and 0.01 at 1 and 3 months, respectively). The bleb analysis revealed a significant reduction in the wall thickness in both groups at 1 and 3 months, which was mostly associated with the hypertensive phase. In group I, the bleb wall thickness decreased from 754.67 ± 53.93 μm in the first postoperative day to 684 ± 81.66 μm and 671.6 ± 69.48 μm at 1 and 3 months, respectively, while in group II, the bleb wall thickness decreased from 707.13 ± 31.7 μm in the first postoperative day to 499.53 ± 99.1 μm and 506 ± 76.91 μm at 1 and 3 months, respectively. There was a significant reduction in AS‐OCT, and bleb reflectivity was insignificant throughout the follow-up period ( $p$ value >0.05). Regarding postoperative complications, the hypertensive phase occurred more frequently in group II (6 eyes, 40%) than in group I (2 eyes, 13.3%). Other complications were also reported more frequently in group II such as hypotony, shallow anterior chamber (AC), and tube exposure. Conclusion. AS-OCT was beneficial in the analysis of bleb morphology after AGV surgery where there were more diffuse functioning multicystic blebs and less thinning in the bleb wall thickness during the hypertensive phase after resection of the Tenon capsule, which might be related to the less incidence of fibrosis around the surgical site.