Restricted post-trabeculectomy bleb formation by conjunctival scarring.

Purpose: To evaluate the effects of radial conjunctival incision during fornix-based trabeculectomy, and conjunctival scarring associated with previous ocular surgeries, for the restriction of bleb formation.
Methods: Digital photo-slit lamp images of filtering blebs, which had undergone fornix-based trabeculectomy with mitomycin C previously, were analysed. The area and the height of the bleb in the conjunctivae with radial incision (Ain and Hin, respectively) were compared with the area and the height of the bleb in the conjunctivae without radial incision (Ano and Hno, respectively). We compared the parameters of bleb area (total bleb area, Ain and Ano) and bleb height (the bleb height at the centre of the scleral flap; Hc, Hin and Hno) in eyes without previous ocular surgeries, with those in eyes that underwent previous ocular surgeries.
Results: The study population consisted of 51 eyes. The Ano and the Hno were significantly larger than the Ain (p < 0.001) and the Hin (p < 0.001) respectively. Subgroup analyses in eyes without previous ocular surgeries and eyes with phacoemulsification cataract surgery also showed that the Ano was significantly larger than the Ain. However, there was no significant difference between the Ano and the Ain in eyes with previous trabeculectomy. A comparison of bleb formation between eyes without previous ocular surgeries and eyes with cataract surgery showed no significant differences in each of the bleb area and bleb height parameters. By contrast, the total bleb area (p = 0.021), the Ano (p = 0.017) and the Hc (p = 0.045) were significantly smaller in eyes with previous trabeculectomy than in eyes without previous ocular surgeries.
Conclusions: Our data demonstrate that bleb formation depends on radial conjunctival incision during fornix-based trabeculectomy and surgical conjunctival scarring from previous trabeculectomy.