ARTIFICIAL MESHWORK (MESH) - CLINICAL AND HISTOLOGICAL STUDY IN THE RABBIT

Purpose Designed to avoid postoperative hypotony that often occurs aft er trabeculectomy and to maintain long lasting filtration, the MESH is a thin porous expended polytetrafluoroethylene (ePTFE) implant that m imics the physiological meshwork. The aim of this study is to assess t he tolerance, biocompatibility mid effectiveness of this device during 6 months in the rabbit. Material and methods We used ail ePTFE with a bout 5 mu m pore size (Zytex). The head of the implant is 3,0 mm,vide and 1,5 mm long and fits in the anterior chamber. The tail is 2,0 mm w ide and 3,0 mm long and fits in the subconjunctival space. The MESH is 250 mu m thick. 24 Dutch pigmented rabbits were selected because thei r dark pigmented iris contrasts with the ePTFE implant giving a better visualization. All the animals were cared for in accordance with ARVO resolutions. Surgery was performed on the right eye by the same surge on (P.H.), the left eye serving as control for IOP measurements. The a nimals were distributed in 3 groups: one with MESH alone (MESH),one wi th MESH and Mitomycin C (MMC), one with MESH and 5-FU (5-FU). Follow-u p was performed every week (W) during 6 months including IOP measureme nt, slit lamp observation, photography and bleb assessment. Histologic al study was done at POD 0 15, 30, 90 and 180 one eye in each group. S tudent t test and alternate Welch t test were used for statistics. Res ults Filtering bleb: no bleb was visible before W3. A bleb was found b etween W3 and W6, decreasing between W6 and W9 with no more change aft er W10. The MESH implant: no change appears in the color of the MESH d uring the study. Some iris pigments OF. synechiae were seen in some ca ses. No extrusion occurred. Intraocular pressure: IOP was lower than i n the control eye. The statistical analysis showed a significant lower pressure for the MESH alone at W5 (p = 0.0069), for the 5-FU group at W1 (p = 0.0326), W2 (p = 0.0488), W4 (p = 0.0312). With Mitomycine C we found very significant results at W1 (p = 0.0073), W2 (P = 0.0136), W4 (p = 0.0497), W9 and W11 (p = 0.0174). After W12 the groups were j oined and IOP was significantly decreased at W17 (p = 0.0376) and W23 (p = 0.0462). Histology confirmed the correct position of the MESH, it s biocompatibility and its ability to drain aqueous humor even if ther e is colonization of the pores by fibroblast-like cells. Conclusion Th e present study has shown that the filtering bleb appeared after 3 wee ks without major hypotony. The material was integrated only in the int rascleral tunnel and was stable. After 6 months the Mesh was well tole rated. This new concept has a simple surgical technique, less invasive than trabeculectomy and required less surgical time. This technique r educed IOP and produced long survival blebs in rabbits. This device ap pears suitable for the surgical treatment of open angle glaucoma.