**1. Introduction**

Penetrating keratoplasty (PK) is a surgical technique in which the full thickness of the recipient cornea is replaced by donor tissue. Deep anterior lamellar keratoplasty (DALK) is intended to selectively replace the abnormal stroma while preserving the recipient's endothelium in place [1]. Therefore, DALK can eliminate the risk of endothelial graft rejection and has minimal detrimental effect on endothelial cell density [2]. Some investigators report that visual acuity and refractive error following DALK can be similar to those following PK [3-6]. Since the introduction of DALK, many surgeons have been accepting donor corneas with lower quality compared with PK. DALK does not rely on quality of the donor endothelium and requires less strict criteria for donor selection [7]. As a result, long-term preservation techniques are being revisited to increase the availability of donor corneas and subsequently alleviate constraints of availability, cost, storage, and transportation in many countries. This feature is imperative in increasing the availability of corneal grafts in regions where there is shortage of donor corneas [7]. The recent alterations in corneal transplantation techniques and consequently the type of donor cornea tissues employed for each technique may require corneal surgeons and eye banks to reevaluate their donor selection criteria.

There is currently a paucity of evidence for setting an acceptable minimum donor conditions for corneal transplantation, especially for lamellar keratoplasty. According to Eye Bank Association of America standards for human corneal transplantation, minimal endothelial cell count limits, the upper and lower limit of donor age, time intervals from death, enucleation or excision to preservation are left to the discretion of the eye banks [8]. An understanding of the effect of donor variables including age, time interval from death to enucleation and preserva‐ tion, storage time, and endothelial cell density both on the quality of donor corneas and on posttransplantation outcomes helps to set eye banking standards. To establish the criteria, it is vital to find out the correlation between these donor parameters and the appropriateness of corneas for transplantation as well as between donor parameters and posttransplantation outcomes. This chapter presents an updated analysis on the type and quality of donor corneas used for PK and DALK, assesses the influence of donor and eye-bank factors on the quality of donor corneas, and furthermore determines whether any of these donor factors affect clinical outcomes, complications, and graft survival.
