Visualization of Blebs Using Anterior-Segment Optical Coherence Tomography after Glaucoma Drainage Implant Surgery

Objective: The current study investigated the internal structure of blebs using anterior-segment optical coherence tomography (AS-OCT) in patients who had undergone Ahmed glaucoma valve (AGV) (New World Medical Inc, Rancho Cucamonga, CA) implantation and compared the differences between successful and failed surgeries. Design: Cross-sectional, observational study. Participants: A total of 76 patients who had undergone AGV implantation. Methods: The blebs after AGV implantation were examined using AS-OCT. The relationship between intraocular pressure (IOP) or the number of glaucoma medications and intrableb parameters was evaluated. Success was defined as IOP <= 21 mmHg with a maximum of 2 glaucoma medications, and the remaining cases were assigned to the "failed surgery group." Logistic regression was used to determine the predictive value of various bleb parameters measured by AS-OCT for bleb success. Main Outcome Measures: The bleb wall thickness (minimum and maximum) and the reflectivity of the bleb wall (mean, modal value, minimum, and maximum). Results: Blebs from 46 successful (60.5%) and 30 failed (39.5%) AGV implantation surgeries were analyzed. The AS-OCT imaging of the intrableb configuration revealed a relatively regular surface and a homogeneous and hyperreflective bleb wall. The maximum and minimum bleb wall thicknesses were significantly different between the 2 groups (P<0.001, P<0.005). No significant differences were observed between the 2 groups in mean, modal, maximum, or minimum reflectivity of the bleb wall. The maximum and minimum bleb wall thicknesses were significantly correlated with the postoperative maximum IOP (r = 0.402, P<0.001; r = 0.280, P = 0.014). The maximum and minimum bleb wall thicknesses showed a significant correlation with the number of postoperative glaucoma eye drops (r = 0.452, P<0.001; r = 0.327, P = 0.004). Maximum bleb wall thickness was significantly associated with the success of AGV surgery by multivariate analysis (P<0.001). Conclusions: Anterior-segment OCT can be used for bleb imaging after glaucoma valve implantation. The AS-OCT results revealed that the maximum bleb wall was significantly thinner in successful AGV implant surgeries compared with unsuccessful AGV implant surgeries. This technique may facilitate the investigation of surgical outcomes and pathogenesis in patients receiving glaucoma valve implants.