Volume of the filtering bleb in prediction of the effectiveness of glaucoma surgery: preliminary results

PURPOSE. To explore the potential for predicting the hypotensive effectiveness of glaucoma surgeries based on the parameters of the filtering bleb (FB) measured using optical coherence tomography (OCT). METHODS. The study included 15 patients (15 eyes) with uncontrolled primary open-angle glaucoma, who underwent standard glaucoma surgery: sinus trabeculectomy with basal iridectomy. Objective assessment of the FB was performed using OCT on postoperative day 2, and then at 7 days, 1 month, and 3 months after surgery. Based on the OCT scans, a three-dimensional model of the FB was constructed, and its volume was calculated. RESULTS. In 3 patients, by the end of the observation period, the FB volume was less than 5.7 mm³, which was associated with an unsuccessful surgical outcome and an increase in intraocular pressure (IOP) to 22.1±3.2 mm Hg. These patients were prescribed hypotensive therapy to achieve target IOP levels. In the other 12 patients, the IOP remained below 14 mm Hg throughout the observation period, with an average IOP of 11.7±2.3 mm Hg. The FB in these patients was diffuse, and its volume exceeded 5.7 mm³. The successful outcome of the surgery allowed for these patients to avoid the need for additional hypotensive therapy. CONCLUSION. Long-term success of glaucoma surgery can be predicted using the threshold filtering bleb volume of 5.7 mm³.