Qualitative and quantitative analysis of filtering blebs with optical coherence tomography

Objective: To provide a qualitative and quantitative analysis of filtering blebs with optical coherence tomography (OCT) in patients after primary trabeculectomy. Design: Evaluation of diagnostic technology. Participants: We retrospectively studied 20 eyes of 20 patients who had a fornix-based flap in primary trabeculectomy: 14 with mitomycin C (MMC) and 6 without MMC. Methods: Filtering blebs were examined using 2 types of OCTs working at a wavelength of 840 and 1310 nm. In this study, we analyzed both the OCT morphologic pattern and the internal structures of blebs, including bleb wall thickness, scleral flap thickness, and the route under the scleral flap, and quantified the reflectivity of the intrableb area. Results: Blebs were classified according to the Hirooka scheme in 3 OCT morphologic patterns: cystoid, diffuse, and layer type. The MMC was associated with the surgical success (100%). A significant association was found between good functionality and cystoid type with both devices: 840-nm OCT (p = 0.02) and 1310-nm OCT (p = 0.04). A significant difference in morphologic patterns was found using the 2 OCTs. There were no significant differences between successful and unsuccessful filtering surgery for intrableb structures. The reflectivity of filtering blebs correlated very well to the postoperative intraocular pressure (IOP; R2 = 0.90; p = 0.001) and to the reduction of IOP (R2 = 0.58; p = 0.001). Our method to quantify the reflectivity showed a significant degree of intergrader consensus (intraclass correlation coefficient = 0.99; < o 0.001). Conclusions: Although 840-nm OCT was not developed to assess the anterior segment, it may be considered a useful tool to evaluate the functionality of blebs in the postoperative period.