Risk factors for developing avascular filtering bleb after fornix-based trabeculectomy with mitomycin C

To investigate risk factors for developing avascular filtering blebs after primary fornix-based trabeculectomy with mitomycin C (MMC).

One-year observational case series. Ninety eyes of 90 patients who underwent primary trabeculectomy with MMC and a fornix-based conjunctival flap were examined. The appearance of the filtering bleb was classified at the last examination into 2 groups: vascular bleb or avascular bleb. Potential predictors that were entered into the model were age at surgery, sex, glaucoma diagnosis, preoperative intraocular pressure (IOP), number of antiglaucoma medications before surgery, use of topical steroid before surgery, duration of MMC application, laser suturolysis, excessive filtration, combination with cataract surgery, and needling revision. IOP was evaluated at 6 and 12 months postoperatively.

Avascular blebs were seen in 28 eyes (31%) at 12 months. Logistic regression analysis revealed that the risk factors for developing avascular blebs after primary fornix-based trabeculectomy included secondary glaucoma [odds ratio (OR)=3.927, P=0.015], excessive filtration (OR=3.215, P=0.043), and not performing laser suturolysis after trabeculectomy (OR=3.597, P=0.031). The mean IOP was decreased from 30.3+/-13.4 mm Hg to 8.8+/-3.9 mm Hg in the avascular bleb group and from 24.6+/-9.9 mm Hg to 10.5+/-3.3 mm Hg in the vascular bleb group at 12 months (P<0.01, both groups, paired t test).

Secondary glaucoma, excessive filtration, and no performance of laser suturolysis after trabeculectomy might be risk factors for development of avascular filtering blebs in primary fornix-based trabeculectomy.