Anterior Lamellar Keratoplasty

lar keratoplasty is not new. Mühlbauer was the first to describe a technique for anterior lamellar keratoplasty (ALK) in 1840.1 Penetrating keratoplasty (PKP) has long been the standard treatment for severe corneal pathology. Lamellar surgery has endured significant technical challenges since its inception. The posterior corneal surface is invisible through an operating microscope, due to the small difference in the refractive index between corneal tissue and aqueous humor. Exposing Descemet’s membrane in lamellar surgery is a painstaking procedure. Diamond blades and micrometers have lessened, but not eliminated, inadvertent perforations. Recent advances in surgical equipment and technique have redefined lamellar corneal surgery. Viscosurgical, microkeratome, and laser advances have improved the ability to expose Descemet’s membrane, and have dramatically reduced surgery time, while improving the safety of the procedure. There is great promise that they will reduce the optical distortion and decreased best-corrected visual acuity.2 The ability to remove corneal pathology, add structural support, and decrease the risk of an immune-mediated graft reaction has caused an upsurge in lamellar keratoplasties.1 There are 2 types of lamellar keratoplasty: anterior and posterior. ALK does not include corneal endothelium, so donor tissue is more easily obtained. This technique enables surgeons to use corneal grafts with low endothelial density. In a recent eye bank study, deep lamellar keratoplasty (DLK) represented 29.8% (85 out of 285) of corneal transplantations. The ability to use previously unsuitable corneas with poor endothelial function permitted a 24.5% increase in corneal grafting in a study by Muraine and colleagues.3 The decreased risk of allograft reaction permits a shorter course of postoperative topical steroid and attendant complications. The anterior stroma is incised using a trephine that can be set to a depth not exceeding the corneal thickness, and stromal layers may be dissected until the desired depth is obtained. Indications include anterior corneal pathology in which the posterior cornea is unaffected. The indications for deep ALK have expanded from keratoconus and hereditary dystrophies (Figure 14-1) to include severe ocular surface disease and cases following infection (Figure 14-2) and corneal perforation. Posterior lamellar keratoplasty was developed because it is believed that by preserving the anterior corneal surface, there will be an overall reduction in refractive error and irregular astigmatism.4 This is especially effective for patients suffering from Fuchs dystrophy (Figure 14-3). Bullous keratopathy is the only absolute contraindication.