**4. Effect of donor and eye-bank variables on clinical outcomes, complications, and graft survivals following PK**

Donor and eye-bank variables have an impact on epithelium-related problems following PK [11, 15, 31-33]. Death-to-preservation time and total storage time were significantly associated with an increased prevalence of epithelial defects on day 1 or hurricane and filamentary keratopathy [11, 15]. Kim et al [31] outlined that the degree of epithelial defect had a statistically significant association with the time interval from preservation to surgery. Borderie et al [32] reported that death-to-storage time, storage time, and deswelling time significantly influenced the graft reepithelialization time in univariate analysis. In multiple regression, however, none of the donor variables significantly influenced the graft reepithelialization time. As for the surface keratopathy 1 week following PK, Mannis et al [33] observed no correlation between this complication and donor age, death-to-preservation time, preservation-to-surgery time, and the donor epithelial status. Therefore, only immediately postoperative epithelium-related complications such as filamentary keratitis and persistent epithelial defects correlate with longer death-to-harvest time and longer storage time.

In addition to donor endothelial status, graft corneal surface is a determinant for the success of corneal transplantation in the postoperative period. Although the donor cornea is ultimately resurfaced by the recipient's epithelium, an intact donor epithelium on postoperative day 1 implies a smoother course after corneal transplantation. An instable graft surface can lead to poor visual acuity due to an irregular tear film interface, discomfort, permanent damage to Bowman's layer, subepithelial scarring, and even infectious keratitis [11].

Another widely investigated correlation is the effect of donor and eye-bank variables on postoperative ECD which yielded contradicting results. Langenbucher et al [13] reported no significant association between the annual endothelial cell loss and the donor age as well as postmortem interval. However, the storage time had a statistically significant correlation with the annual endothelial cell loss. Parekh et al [19] reported postmortem interval ≥ 10 hours tends to have a higher percentage of endothelial cell loss than < 10 hours of interval at both 1 year and 3 years postoperatively. Postoperative higher ECD values were significantly associated with higher baseline ECD and younger donor age in one study [34]. When the follow-up period was extended to 10 years, the study group observed that the donor age influenced ECD, although this finding was primarily influenced by a small group of the youngest donors (12 to < 34 years of age) that had the least cell loss and the best graft survival [34]. Lass et al [10] observed that younger age and female gender of the donor had a significant correlation with higher ECD over time. However, cause of death and time interval from death to preservation or to surgery failed to demonstrate any significant association with changes in ECD during follow-up [10]. One study found a statistically significant negative influence of postmortem time and donor age on chronic loss of endothelial cell density after PK for keratoconus [35]. Because endothelial cell graft attrition takes place at an accelerated rate [36], a higher initial endothelial cell density of the donor tissue can improve long-term graft survival [34]. Older donor age and longer storage time are more likely to be associated with lower ECD but, as long as the ECD is greater than a given minimum at the time of corneal transplantation, these parameters will have insignificant influence on long-term graft survival. The Cornea Donor Study results indicate that donor age is not an important factor in most penetrating kerato‐ plasties performed for endothelial disease [37]. Therefore, functional and cellular results of PKs are not dramatically influenced by very old donor age and the very elderly should not be deemed off limits for corneal procurement.

no significant correlation with the percentage of endothelial cell loss. However, the preservation time demonstrated a significant correlation with a loss of 0.07% for each day

Additionally, the combined effects of cause of death and donor age on ECD were evaluated. It was identified that chronic and long-lasting, severe diseases like cancer reduced ECD to a greater extent as compared to diseases causing a more rapid death. This negative impact of chronic diseases was aggravated by the general reduction in ECD observed with increasing

Donor and eye-bank variables have an impact on epithelium-related problems following PK [11, 15, 31-33]. Death-to-preservation time and total storage time were significantly associated with an increased prevalence of epithelial defects on day 1 or hurricane and filamentary keratopathy [11, 15]. Kim et al [31] outlined that the degree of epithelial defect had a statistically significant association with the time interval from preservation to surgery. Borderie et al [32] reported that death-to-storage time, storage time, and deswelling time significantly influenced the graft reepithelialization time in univariate analysis. In multiple regression, however, none of the donor variables significantly influenced the graft reepithelialization time. As for the surface keratopathy 1 week following PK, Mannis et al [33] observed no correlation between this complication and donor age, death-to-preservation time, preservation-to-surgery time, and the donor epithelial status. Therefore, only immediately postoperative epithelium-related complications such as filamentary keratitis and persistent epithelial defects correlate with

In addition to donor endothelial status, graft corneal surface is a determinant for the success of corneal transplantation in the postoperative period. Although the donor cornea is ultimately resurfaced by the recipient's epithelium, an intact donor epithelium on postoperative day 1 implies a smoother course after corneal transplantation. An instable graft surface can lead to poor visual acuity due to an irregular tear film interface, discomfort, permanent damage to

Another widely investigated correlation is the effect of donor and eye-bank variables on postoperative ECD which yielded contradicting results. Langenbucher et al [13] reported no significant association between the annual endothelial cell loss and the donor age as well as postmortem interval. However, the storage time had a statistically significant correlation with the annual endothelial cell loss. Parekh et al [19] reported postmortem interval ≥ 10 hours tends to have a higher percentage of endothelial cell loss than < 10 hours of interval at both 1 year and 3 years postoperatively. Postoperative higher ECD values were significantly associated with higher baseline ECD and younger donor age in one study [34]. When the follow-up period

Bowman's layer, subepithelial scarring, and even infectious keratitis [11].

**4. Effect of donor and eye-bank variables on clinical outcomes,**

**complications, and graft survivals following PK**

longer death-to-harvest time and longer storage time.

of preservation [19].

80 Advances in Eye Surgery

age [30].

Despite contradictory results of studies evaluating the effect of donor and eye-bank variables on postoperative ECD and morphology, the majority of studies showed that donor preserva‐ tion method and time, donor age, cause of death, and preoperative donor ECD and/or morphometric measures (coefficient of variation and hexagonality) had no influence on overall graft failure [12, 14, 26, 38-41]. However, one study reported that preoperative risk factors for developing late endothelial failure included low ECD and older donor age [16]. Authors from the Cornea Donor Study observed that grafts from donors aged between 66 and 75 years that met the eligibility criteria of their study had a 5-year graft survival rate, comparable to grafts from younger donors [9]. However, higher donor age was significantly associated with lower graft success during a longer follow-up period [37].

Two studies reported the effect of donor age on visual outcomes. Gain et al [26] found no significant difference between the two groups (donors younger than 85 years and donors aged 85 years and older), in terms of visual acuity and astigmatism. Halliday et al [42] found no significant correlation between the time taken to reach a postoperative acuity of 6/12 and the age of donor. One study reported that donor age, ABO compatibility, and other donor factors were not associated with graft rejection [43]. Younger donor age, however, was found to be a risk factor for graft rejection (but not for graft failure) by three other studies [26, 40, 44].
