[Artificial trabeculum (MESH). Clinical and histological study in the rabbit].

PURPOSE

Designed to avoid postoperative hypotony that often occurs after trabeculectomy and to maintain long lasting filtration, the MESH is a thin porous expended polytetrafluoroethylene (ePTFE) implant that mimics the physiological meshwork. The aim of this study is to assess the tolerance, biocompatibility and effectiveness of this device during 6 months in the rabbit.

MATERIAL AND METHODS

We used an ePTFE with about 5 microns pore size (Zytex). The head of the implant is 3,0 mm wide and 1,5 mm long and fits in the anterior chamber. The tail is 2,0 mm wide and 3,0 mm long and fits in the subconjunctival space. The MESH is 250 microns thick. 24 Dutch pigmented rabbits were selected because their 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 surgeon (P.H.), the left eye serving as control for IOP measurements. The animals were distributed in 3 groups: one with MESH alone (MESH), one with MESH and Mitomycin C (MMC), one with MESH and 5-FU (5-FU). Follow-up was performed every week (W) during 6 months including IOP measurement, slit lamp observation, photography and bleb assessment. Histological study was done at POD 0, 15, 30, 90 and 180 one eye in each group. Student t test and alternate Welch t test were used for statistics.

RESULTS

Filtering bleb: no bleb was visible before W3. A bleb was found between W3 and W6, decreasing between W6 and W9 with no more change after W10. The MESH implant: no change appears in the color of the MESH during the study. Some iris pigments or synechiae were seen in some cases. No extrusion occurred. Intraocular pressure: IOP was lower than in 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 joined and IOP was significantly decreased at W17 (p = 0.0376) and W23 (p = 0.0462). Histology confirmed the correct position of the MESH, its biocompatibility and its ability to drain aqueous humor even if there is colonization of the pores by fibroblast-like cells.

CONCLUSION

The present study has shown that the filtering bleb appeared after 3 weeks without major hypotony. The material was integrated only in the intrascleral tunnel and was stable. After 6 months the Mesh was well tolerated. The new concept has a simple surgical technique, less invasive than trabeculectomy and required less surgical time. This technique reduced IOP and produced long survival blebs in rabbits. This device appears suitable for the surgical treatment of open angle glaucoma.