Effect of trephination technique on the ultrastructure of corneal transplants: guided trephine system upsilon posterior punch technique

Aim-Different trephination methods may lead to differences in degree of tis sue damage and endothelial cell loss, which both influence the outcome of p enetrating keratoplasty. Light, transmission, and scanning electron microsc opy were used to compare the ultrastructural appearance of the cut edges an d the endothelial cell loss in 26 human corneal donor buttons obtained by t rephination with the suction fixated guided trephine system (GTS) and with the free hand posterior punch technique (PPT). Methods-Human corneas were stored between 5 and 14 days in Optisol. One cor nea from each pair was used for each technique. Trephinations (7.5 mm) were performed either from the anterior direction with the GTS (n=13) or from t he posterior direction with the PPT (n=13) using Pharmacia Superblade treph ines. Light microscopy, transmission electron, and scanning electron micros copy were performed according to standard procedures. Widening of the cut e dges and the extent of endothelial cell loss were measured at three differe nt areas per corneal button and analysed statistically. Results-In contrast with the PPT, the GTS trephine produced considerable fi brillar disorder at the cut edges of the corneal buttons. The distance to w hich the endothelial cell loss extended from the edges of the cuts was sign ificantly (p<0.001) lower for the GTS (42.2 (SD 50.8) mu m from the edge) t han for the PPT (109.3 (68.1) mu m). Stromal widening at the edges (measure d as percentage increase in stromal thickness, compared with the thickness of the central corneal was observed with both techniques. However, the mean stromal widening produced by the GTS was significantly greater than that p roduced by PPT (106% (24%) v 69% (21%); p<0.002). Conclusion-Both trephination techniques produced only minor tissue damage. Nevertheless, there were distinct differences in the fine appearance of the cuts produced by the GTS and the PPT techniques. The extent of the fibrill ar dislocation and stromal widening was greater at the edges of the GTS but tons. The GTS technique produced significantly less endothelial cell loss a t the cut edges than did the free hand punching technique, PPT.