Histological and ultrastructural findings of corneal tissue after failed descemet membrane endothelial keratoplasty

Abstract

To investigate in a retrospective review the histological and ultrastructural findings after failed primary and early Descemet membrane endothelial keratoplasty (DMEK), propose possible pathomechanisms of graft failure and give clinical implications. The explanted grafts underwent light- and electromicroscopical investigations in eight failed DMEK cases. Haematoxylin - Eosin, periodic acid Schiff and Alcian blue stainings were performed. Special note was given to any residual stromal remnants, absence of endothelial cells, lamellar structure and 'activation' of keratocytes. Of the eight cases, six were re-DMEKs and two penetrating keratoplasties. Partial graft separation was seen in six and no graft separation in two of the cases. The average time-interval to the re-DMEK or penetrating keratoplasty was 4.6 months. Light and electron microscopy of the two explanted stromal specimens showed varying degrees of keratocyte activation. Endothelial cell loss was observed in essentially all explants with varying degrees and positive correlation with intraoperative difficulty. Assumed upside-down situations showed large areas of intact endothelial cells. In addition, a new layer, situated between the endothelial cell layer and the posterior nonbanded layer, was observed with loose intercellular structure. A loss of the endothelial cell layer of varying degrees and positive correlation with intraoperative difficulty are the prominent feature of primary and early DMEK graft failure. Of note is the upside-down situation, in which in some cases, the endothelial cell layer not only remains intact but also demonstrates metabolical activity in forming a novel cellular layer.