The number of keratoplasties increases every year, and the number of patients on the waiting list for corneal transplantation continues to rise. According to the LIONS Eye Bank data, 609 corneas were transplanted in 2019 at the Department of Ophthalmology of the UKS in Homburg/Saar and 652 were transplanted in 2020 (Fig. 3). The number of deceased persons increased from 925 in 2010 to 1214 in 2019, while the proportion of consents has remained at around one quarter, resulting in 15–21% explantations over the last decade. In 2019, 359 people donated 715 corneas after their death, while there were 349 patients on the waiting list for a transplant in Homburg alone. Overall, around 5000 patients across Germany are still waiting for a donor cornea, and, the number of corneas donated at UKS obviously is not enough.
This situation explains why the trend is to acquire ready-to-use corneas bought from external facilities, as the percentage of corneas being prepared for transplantation by the Eye Bank has not kept pace. For various specific reasons, the department in Mainz was the major source of corneas at first, followed later by Aachen and DGFG, and most recently Rostock .
Several factors can influence the willingness to donate corneas and tissue suitability for transplantation. In the absence of a previously expressed wish for or against organ donation, the physician in charge of the treatment or a medical employee of the Eye Bank asks the deceased’s next of kin about the presumed will of the deceased. In a difficult situation of grief and despair, such a question can lead to additional stress, which may in turn influence the decision and result in the refusal of the corneal explant [11, 17]. In our study, an average of 23.3% of the family members of the deceased person agreed to the corneal donation, and 55.3% declined it. The emotionally difficult situation after the death of a close relative, together with limited knowledge about procedures for transplantation, brain death-related problems, and tissue suitability after the death of a potential donor, may lead to an unwillingness to donate [14].
A positive development is the much higher number of people with organ donor cards in Germany, at 39% in 2020 compared with 12% in 2004 [14]. Thus, an examination of decision trends in years is important. Of note, the willingness to donate may differ depending on socioeconomic group and country region, as analyzed by Uhlig et al. in three studies [10,11,12]. Their three separate analyses had something in common: most of the participants expressed an intention to donate corneas post-mortem as well as an interest in receiving additional information about donation and suggested the Internet as the most appropriate source of information on this subject.
As part of our selection process, we first obtained the consent of all potential donors and then clarified possible contraindications. This sequential procedure explains why not all corneas consented for harvest were harvested. Despite consent to corneal donation, we do not explant corneas after 24 h following death. German regulations, which are based on EU regulations, preclude taking the blood sample required for analysis after this time. Therefore, another factor in whether corneas are harvested can be a delayed report of a death to our Eye Bank, which would make the timely collection of the cornea impossible. For this reason, it is essential to continuously work on improving communication among different departments to avoid the loss of potential donors because of organizational problems.
All corneas were closely examined prior to their use in surgery. Examinations were done either at the LIONS Eye Bank or externally, depending on the tissue source. According to German regulations, the minimum ECC required is 2000 cells/mm2 for keratoplasty and 1000 cells/mm2 for urgent keratoplasty or anterior lamellar keratoplasty. In our ophthalmology department, we use only transplants with >2000 cells/mm2 for deep anterior lamellar keratoplasty because of the risk of intraoperative endothelial perforation with the need to convert the operation to penetrating keratoplasty [23], and we use >2200 cells/mm2 for DMEK. Additional requirements for DMEK are no donor diabetes and a donor age > 55 years. Kramp et al. examined 4140 corneas for factors possibly influencing the suitability and, in some cases, leading to discarding of donor corneas [20]. Based on their findings, information about cataract surgery, diabetes, chemotherapy or causes of death such as sepsis in the donor history should be obtained, although this history does not necessarily reduce the suitability of corneal donor tissue. These conditions as well as the results of the conjunctival swab and serology will define the final suitability of the tissue.
The introduction in November 2010 of a quality management system at the LIONS Eye Bank had a major impact on the rate and reasons for discarding corneas, thanks to improved standards, protocols, and training [24]. After evaluation of 4140 corneas between 2006 and 2016, Laun, Kramp et al. reported that the rate of discarded corneas because of poor endothelial quality, contamination of the medium, or positive conjunctival swab decreased significantly from 50.1 to 39.7%. Similarly, we found that 52% of corneas were discarded in 2009, compared with 36% in 2019. The main reason for discarding of corneas tended to be an insufficient ECC, followed by a positive conjunctival swab for fungal rather than for bacterial contamination and finally by the serology. However, the endothelial quality as the main cause of tissue rejection has shown a downward trend over the last decade, with 36% being discarded in 2009 and only 11% in 2019. The reasons for this continuous decrease are multifactorial. One factor could be additional quality controls at the Eye Bank [24] that tended to improve graft quality but could have resulted in discarding of the cornea prior to ECC measurement. Better ECC may be attributable to improved eye surgery techniques (minimally invasive procedures, endothelial protection using viscoelastics for cataract surgery) or to Eye Bank procedures such as cooling of donor bodies before cornea collection, shorter time between death and collection (typically <12 h versus 3 days in 2009), and an improved cultivation process (cleanroom since 2019). It is also plausible that compared with 2009, from 2015 we were able to better assess donor endothelium with a new inverted specular microscope (Primovert, Co. Zeiss) and an analysis tool assisting technicians in evaluating endothelial cells (REA XDL, Co. Robin), potentially leading to fewer discarded corneas. In addition, regular training of Eye Bank technicians who had been continuously replaced over the decade and the predominance of these technicians in doing the harvesting rather than less experienced residents could have resulted in less endothelial damage and thus less ECC-based discarding.
The conjunctival swab for fungi became a part of the diagnostics in 2014, as did a more detailed serology examination, including testing for hepatitis B/C, HIV, and syphilis. These results show how important critical selection and additional testing are to ensure the best transplant quality .
Li et al. analyzed the correlation between positive conjunctival swabs and microbial contamination of the culture medium, where donor corneas are held prior to transplantation [25]. They found a significantly higher contamination rate of the culture medium in cases of contaminated conjunctival swabs, which was subsequently a reason for discarding the tissue, as we found in the current work. The timing of post-mortem blood sample collection, the time between death and corneoscleral button excision, and storage time all seem to be important factors as well [20, 26]. Kramp et al. found that when blood sample collection took place more than 12 h after death, corneas were discarded more often because of positive donor serology [20]. According to Röck et al., a prolonged time from storage and death to corneoscleral button explantation is associated with an increased risk of tissue unsuitability for transplantation. Because we remove corneoscleral buttons up to 24 h after cardiac arrest, it could be beneficial to consider tissue removal in the first 12 h after death [26].
Compared to the findings of Schaub et al. who reported 235 (5.1%) corneas from 4593 patients, donated after death from 2011 and 2015 [27], we found that 1748 (17%) corneoscleral buttons were donated from 10,265 deceased persons in the UKS between 2010 and 2019. The increasing absolute number of corneas explanted in our department seems to be quite favorable and promising. This observed growth in corneal explants also may have resulted from the practice of performing corneal explants daily, including on non-working days. Doctors on duty during weekends or holidays checked the routine online report of deceased persons every morning through the internal hospital information system and, in the absence of objections to the corneal explantation, ensured that corneas were obtained right away.