Factors influencing the filtration-bleb volume after Ex-PRESS(®) surgery

PURPOSE: The aim of this study was to investigate the factors influencing the volume of the filtration bleb after Ex-PRESS(®) surgery. METHODS: This was a retrospective non-randomized study. After excluding patients who had undergone an additional glaucoma surgery, 99 glaucoma patients who underwent Ex-PRESS(®) surgeries and were followed up for >2 years were analyzed. We used anterior segment optical coherence tomography to measure the bleb volume, and compared the volume at 1 year with that at 2 years after surgery. We also examined potential influencing factors, including age, number of medications, central corneal thickness, type of glaucoma, preoperative intraocular pressure (IOP), postoperative IOP, reduction ratio of IOP, history of trabeculotomy, and operation method (Ex-PRESS(®) surgery only or simultaneous cataract surgery). RESULTS: Ex-PRESS(®) surgeries significantly decreased the IOP from 26.3±9.7 mmHg to 11.6±3.7 mmHg after 24 months (P<0.001). The success rate at 2 years was 81.2% (IOP ≥21 mmHg or ≥20% reduction from the baseline IOP). The results showed that age, postoperative IOP, glaucoma type, and simultaneous cataract surgeries influenced the filtration-bleb volume. CONCLUSION: Advanced age, higher postoperative IOP, pseudo-exfoliation glaucoma, and simultaneous cataract surgeries were all found to decrease the volume of the filtration bleb.