Nanothin Descemet Stripping Automated Endothelial Keratoplasty

Introduction

Allowing for selective replacement of the diseased endothelium, endothelial keratoplasty procedures, such as Descemet membrane endothelial keratoplasty (DMEK) and Descemet stripping (automated) endothelial keratoplasty (DSAEK or DSEK), have become the preferred treatment for endothelial dysfunction. Despite growth in popularity, DMEK can present both surgical difficulty (more technically demanding and steeper learning curve) and unpredictability; this has limited its widespread adoption. As a result, DSAEK remains the most popular endothelial keratoplasty technique in the United States.

In DSAEK, the diseased endothelium is removed and replaced by a donor graft consisting of a layer of deep stroma of variable thickness, Descemet membrane, and healthy endothelial cells. Overall visual acuity and rejection rates for traditional DSAEK have been shown to be inferior when compared with DMEK. This is often attributed to the fact that DSAEK transplants retain a variable degree of stroma in addition to Descemet membrane and endothelium compared with DMEK (a pure anatomic replacement of Descemet membrane and endothelium). Neff et al. were the first to report that thinner DSAEK grafts (≤131 μm) demonstrated better postoperative best corrected visual acuity (BCVA) compared with thicker (>131 μm) DSAEK grafts, with greater percentages of thinner DSAEK eyes achieving 20/20 and 20/25 compared with thicker DSAEK eyes. Subsequent studies found conflicting results regarding the relationship between DSAEK graft thickness and visual acuity. However, these studies were mainly retrospective, and the subgroup cutoff values of compared graft thicknesses varied between studies.

Quality of vision has also been shown to be superior with thinner DSAEK grafts, as graft thickness has been correlated with graft asymmetry and associated higher order aberrations. Dickman et al. demonstrated that thinner DSAEK grafts had less irregularities and induced less optical aberrations. Besides graft thickness, factors such as stromal scarring, interface opacity, graft shape, posterior curvature, and total corneal thickness may all play a role in the overall visual outcomes in DSAEK.