Keratoplasty: Moving to the Front

Penetrating keratoplasty (PKP) has a long track record of high success rates compared to other tissue and organ transplantations. Despite the immunologic privilege of the cornea, the issue of immunological rejection cannot be overlooked and endothelial rejection is observed in up to 20% of eyes undergoing PKP. 1 Repeat keratoplasties after rejection are increasingly more prone to rejection and the potential for a clear cornea becomes progressively lower with subsequent PKPs. Prospective long-term graft survival studies have also revealed disappointing results with PKP, and it is now recognized that graft survival rates and endothelial cell counts continue to decrease for many years after PKP. 2 Recent advances in surgical technique have prompted a resurgence of lamellar corneal transplant techniques that aim to selectively replace only diseased layers of the cornea. Lamellar keratoplasty (LK) involves replacing either the anterior stroma (anterior lamellar keratoplasty, ALK) or posterior deep stroma and endothelial layer (posterior lamellar kera-toplasty, PLK or endothelial keratoplasty, EK). In this issue of JOVR, Javadi et al 3 report the results of ALK using the big bubble technique in patients with keratoconus with excellent results that are comparable to, if not better than, traditional PKP. The advantages of ALK over conventional PKP are well recognized. 4,5 Since ALK is largely a nonpenetrating extraocular technique, it reduces the incidence of intraocular complications such as glaucoma, cataract formation, retinal detachment, cystoid macular edema, endoph-thalmitis and expulsive hemorrhage. Leaving an intact and healthy recipient endothelial bed obviates problems related to endothelial rejection. The integrity of Descemet's membrane is not violated with LK, therefore a tectonically stronger corneal wound is achieved. Fewer su-tures and thus less suture-related astigmatism has likewise been reported in lamellar grafts as compared with PKP. Despite the distinct advantages of ALK, PKP has remained the most common corneal grafting procedure. Currently, about 50,000 cor-neal transplants are performed each year in the United States alone, 6 and according to the latest statistics from the Eye bank Association of America, 2% of all cornea transplants were ALK, 70% PKP, and 28% EK. 6 One of the main criticisms of ALK has been suboptimal visual acuity compared with PKP caused by interface problems, irregularity of the lamellar dissec-tion, and residual scarring. These problems have largely been eliminated by new deep ALK techniques which allow removal of the entire corneal stroma down to a bare Descemet's membrane, leading to improved visual outcomes. 4,5 Deep anterior …