Some aspects of filtering bleb formation in patients with primary open-angle glaucoma after non-penetrating deep sclerectomy

PURPOSE. To determine the role of extracellular matrix (ECM), transforming growth factor β (TGF-β) and matrix metalloproteinase 9 (MMP-9) in the mechanisms of filtering bleb formation after non-penetrating deep sclerectomy (NPDS) in patients with primary open-angle glaucoma (POAG).METHODS. The study consisted of prospective examination of 65 patients with POAG operated by the NPDS method. Three groups were formed: group 1 — optimal hypotensive effect of NPDS (21 patients); group 2 — relative hypotensive effect (23 people); group 3 — absence of hypotensive effect (21 patients). During the postoperative period, the condition of the intraocular fluid outflow pathways was evaluated with ultra biomicroscopy, optical coherence tomography, level of intraocular pressure, as well as the concentrations of TGF-β and MMR-9 in the tear and aqueous humor.RESULTS. The anterior chamber aqueous humor was found to contain TGF-β in all patients with glaucoma. Group 1 was noted to have minimal initial TGF-β concentrations in the tear and aqueous humor, high MMR-9 level in the pre- and postoperative period. Sparse extracellular matrix was the substrate for the filtering blebs. Group 2 was revealed to have elevated initial concentrations of TGF-β in the tear and aqueous humor, extremely high level of MMP-9 in the aqueous humor, accumulation of MMP-9 in the tear after 2 weeks, and inhibition of TGF-β and MMP-9 two months after NPDS. In the early period, loci of rigid ECM were visualized in the filtering blebs, but functional outflow pathways were successfully formed by month two after additional therapy. Group 3 was established to have maximum TGF-β concentrations and low MMP-9 concentrations in the anterior chamber aqueous humor, a decrease in tear MMP-9 after two weeks, and inhibition of TGF-β and MMP-9 two months after NPDS. In the early postoperative period, the filtering blebs were based on rigid ECM, by month two there was scar deformation of the outflow pathways.CONCLUSION. The important conditions for the formation of functional filtering blebs after NPDS are the structural organization of temporary ECM of the filtering blebs in the early postoperative period and the timely degradation of ECM components with predominant concentration of MMR-9 over TGF-β.