Filtering blebs structure and function evaluation using optical coherence tomography

Abstract

Purpose: To assess the ability of a noncontact optical coherence tomography to evaluate the morphological features of filtering blebs one year after glaucoma surgery.Design: Prospective study.Methods: Eighteen patients (18 eyes) with diagnosed primary open-angle glaucoma (POAG) assigned for trabeculectomy were included in the 12-month study carried out in the Eye clinic of the Lithuanian University of Health Sciences. All participants underwent trabeculectomy with 5-fluorouracil (5-FU). Bleb function was considered to be successful if the intraocular pressure (IOP) was ≤ 18 mmHg without glaucoma medications and a limited success if: 18 < IOP ≤ 21 mmHg with or without glaucoma medications at 12 months after surgery. The filtering blebs were imaged by anterior segment optical coherence tomography (AS-OCT) to evaluate the bleb wall reflectivity and measured bleb structures 12 months after trabeculectomy. Level of significance: p < 0.05 was considered significant.Results: The mean preoperative IOP was 25.7 (6.5) mmHg and the mean number of topical glaucoma medications was 3.0 (1.2). After surgery the mean IOP was 13.8 (3.4) mmHg and glaucoma medication was 0.3 (1.0) (Wilcoxon test, p < 0.001). Analyzing bleb morphology and bleb function it was found that with uniform wall reflectivity 0 out of 3 eyes (0%) had successful bleb function and with multiform wall reflectivity 14 out of 15 eyes (93.3%) had successful bleb function 12 months after surgery (p = 0.005).We found positive correlation between IOP changes and bleb wall thickness, height of internal fluid-filled cavity (bleb height) and total bleb height (r = 0.875, 0.897, 0.939, p < 0.001).Conclusion: AS-OCT is a useful device to assess the structure of the filtering bleb. Larger internal fluid-filled cavity, total bleb height, bigger bleb wall thickness and multiform bleb wall reflectivity were found to be good indicators of bleb function.