Ultrathin and Femtosecond Descemet Stripping Automated Endothelial Keratoplasty

Abstract

SUMMARY T he standard surgical treatment of corneal endothelial failure used to be a full thickness replacement of the destroyed endothelium by a penetrating Keratoplasty (PK). PK elicits a clear cornea, but it entails two major drawbacks: being a full thickness vertical corneal section which results in a tectonically unstable graft, and the graft is fixed in place with sutures which result in astigmatism, slow visual rehabilitation, in addition to other complications as infection, vascularization and persistent epithelial defects. During the past decade, endothelial keratoplasty (EK) has supplanted PK as the procedure of choice for treating corneal endothelial dysfunction. Descemet stripping automated endothelial keratoplasty (DSAEK) gained favor when surgeons began dissecting donor tissue with a microkeratome and eye banks began providing precut donor tissue. Since 2007, DSAEK has been the standard of care, amounting to about 80 percent of endothelial corneal transplants performed in the Untied States. Endothelial keratoplasty involves removal only of diseased endothelium along with (DM) through a corneoscleral or corneal incision. Folded donor tissue is introduced through the same small (2.8-5.0mm) incision. DSAEK uses an automated microkeratome to prepare donor tissue and is currently the most commonly performed techniques. Selective replacement of the dysfunctional posterior portion of the cornea offers distinct advantages compared with penetrating keratoplasty, including faster visual rehabilitation, improved surface topography with reduction of post-surgical astigmatism, reduced risk of expulsive hemorrhage as this procedures occur in closed – system, reduced immunologic rejection against the grafted endothelium due to the reduced amount of foreign surface antigens on the recipient cornea, and the presence of the recipient cornea’s own anti-inflammatory and antiangiogenic corneal epithelium. In 2009, at the annual meeting of the cornea society in Sa Francisco, a new approach to DSSAEk surgery was presented aimed at utilizing what named “ultra-thin” (UT) DSAEk grafts. In this procedure, the surgical technique differs substantially from conventional DSAEk, both in the preparation and in the manipulation and delivery of the graft. In fact, the UT graft is created with two microkeratome passes, the first one to debulk the donor tissue and the second one to cut down the final thickness to about 100 micrometers. This is an easy to perform and widely applicable procedure to obtain reproducible results with the use of the microkeratome, which still remains the only instrument that can guarantee optimal smoothiness of the stromal surface to DSAEk grafts. The femtosecond laser is a recent innovation that can be programmed to produce bladeless, precise lamellar cuts at any depth with accompanying trephination cuts for both anterior and posterior lamellar transplantion. With precise computer-controlled laser energy, the FS Laser is capable of cutting lamellar, axial, or pocket cuts at different desired depths and diameters in the cornea. The ability of the femtosecond laser to cut cornea is less affected by its cloudiness, making it ideal for treating edematous corneas. FSL-assisted DSEK was effective in treating endothelial failure with minimal induced refractive astigmatism and a mild hyperopic shift in refraction as the posterior lamellar disc is thinner in the center and thicker at the edges.