SupraDescemetic Synthetic Cornea (sDSC). Medium-Term Biocompatibility Study

Abstract

Abstract: : Purpose: To assess feasibility and biocompatibility of an sDSC in a rabbit model. Methods: sDSC (7 mm ∅, 450 µm thick central optical zone, 100 µm outer flange) of 4 different materials {PMMA (n=4), HEMA-MMA26 (n=4), HEMA-MMA34 (n=2), and HEMA-NVP75 (n=1)} were successfully implanted in the right eyes of 11 NZW rabbits. Two surgical approaches were tested. Following intralamellar dissection and trephination (3.7 mm ∅) of the upper 85% of the cornea, resection of the remaining stromal layers was performed until Descemet's membrane (DM) was fully exposed. Animals of group A (n=3) received mesoplants with their base located completely on bare DM, animals of group B (n=8) were implanted with the flange of the implant located in deep stroma (85%) and the optical part on bare DM. Biomicroscopy was performed on the first 3 days and weekly thereafter to assess biocompatibility and extent of fibrosis underneath the mesoplant. Group B animals were euthanized for histology at 2 months. Results: Group A mesoplants showed a postoperative tendency for decentration and instability. One rabbit of this group lost its implant spontaneously 36 days after surgery, leaving DM still intact. Tissue glue fixation of the flange to the stroma performed in the two other rabbits of this group in order to prevent decentration failed and produced neovascularisation and inflammation in 1 case. The group B surgical technique resulted in better mesoplant stability and optical centration and none of the rabbits developed any neovascularisation or inflammation. DM was found firmly attached to the posterior surface of the optic. Moderate retraction of corneal tissue was found above the outer flange, mostly at the 6 and 12 o'clock position. The denuded DM remained transparent over time. Indirect ophthalmoscopy performed through the artificial cornea allowed accurate examination of the posterior pole. Surgery could be completed successfully with implantation of an sDSC in 16 of 17 eyes (94%) in a feasibility study on human eye bank eyes. Conclusions: Implantation of a supra-Descemetic artificial cornea on top of a denuded DM is feasible, presenting both biocompatibility and maintenance of transparency of DM over a 2 months observation period. Support: European project BMH4-CT97-9507, Florida Lions Eye Bank, Research to Prevent Blindness NY, Henri and Flore Lesieur Foundation, FWF Austrian Science Fund

Keywords: keratoprostheses • cornea: basic science • microscopy: light/fluorescence/immunohistochem