Use of glycerol-preserved corneas for corneal transplants

Efficacy of Emergency Penetrating Keratoplasty with Cryopreserved Human Donor Corneas

INTRODUCTION

To investigate the long-term outcomes of emergency penetrating keratoplasty using cryopreserved human donor corneas in the management of actual or imminent corneal perforation.

METHODS

A retrospective analysis was performed of the treatment efficacy of emergency penetrating keratoplasty using a cryopreserved human donor cornea, in 14 eyes of 14 patients with corneal ulcers of different etiology. For comparison, the medical histories of 14 patients who had undergone penetrating keratoplasty with the same indication, but received a regularly processed human corneal graft, were retrospectively analyzed. In both groups, the primary endpoint for graft failure was repeat surgery, defined as the necessity for amniotic membrane transplantation, conjunctival flap, or repeat penetrating keratoplasty, during a follow-up time of maximally 12 months.

RESULTS

The difference in the need for repeated surgeries between the cryopreserved human donor cornea group and cultivated tissue graft group was not statistically significant (p = 0.835). Specifically, repeat complex surgery of any kind within 6 months was necessary in 50% of the cryopreserved cornea group and in 57.1% of the control group, with no further surgical interventions during the remainder of the follow-up period. However, repeat penetrating keratoplasty occurred more frequently in the cryopreserved cornea group (n = 5) than in the control group (n = 1) during the first 12 months after treatment (p = 0.048).

CONCLUSION

Cryopreserved corneas appear to be a viable option for promptly addressing emergencies and stabilizing the corneal situation, providing a faster solution compared to waiting for fresh tissue availability. However, repeat penetrating keratoplasty is more frequent when cryopreserved human donor corneas are used. Cryopreserved human donor corneas may be useful if surgical treatment is urgent and alternative options, such as tissue use, a conjunctival flap, or multilayer amniotic membrane transplantation, are not available.

A proposed model of xeno-keratoplasty using 3D printing and decellularization

Corneal opacity is a leading cause of vision impairment and suffering worldwide. Transplantation can effectively restore vision and reduce chronic discomfort. However, there is a considerable shortage of viable corneal graft tissues. Tissue engineering may address this issue by advancing xeno-keratoplasty as a viable alternative to conventional keratoplasty. In particular, livestock decellularization strategies offer the potential to generate bioartificial ocular prosthetics in sufficient supply to match existing and projected needs. To this end, we have examined the best practices and characterizations that have supported the current state-of-the-art driving preclinical and clinical applications. Identifying the challenges that delimit activities to supplement the donor corneal pool derived from acellular scaffolds allowed us to hypothesize a model for keratoprosthesis applications derived from livestock combining 3D printing and decellularization.

Therapeutic and tectonic keratoplasty with simple cryopreserved remnants of donor corneas: an 11 year retrospective case series

This study sought to describe the use of deep-frozen donor corneal remnants preserved after keratoplasty procedures for therapeutic or tectonic keratoplasty without subsequent optical keratoplasty. This single-center retrospective consecutive case series analyzed the electronic medical records of patients who had undergone therapeutic or tectonic keratoplasty using deep-frozen donor remains preserved in Optisol-GS, for the past 11 years at Keimyung University Dongsan Medical Center. Fifty-five surgical cases in 46 patients were included. Twenty-three surgical cases in 18 patients underwent therapeutic keratoplasty for refractory infectious corneal ulcer. Complete eradication of primary infection was achieved in 14 patients (77.8%). Tectonic keratoplasty were performed 32 cases in 28 patients. Twenty-seven of 28 patients were ultimately able to maintain anatomical integrity (96.4%). Mean uncorrected visual acuity improved from 1.77 ± 0.94 preoperatively to 1.31 ± 0.95 at the last follow-up postoperatively in the tectonic graft group by logarithm of the minimal angle of resolution (P = 0.002). There were no cases of graft rejection. Keratoplasty using cryopreserved donor tissue is a suitable surgical alternative for infectious or non-infectious corneal ulcers in elderly patients or patients with poor general condition. It could be a viable alternative to overcome the shortage of corneal donors.

Ultrastructural Analysis of Rehydrated Human Donor Corneas After Air-Drying and Dissection by Femtosecond Laser

Purpose: To evaluate the efficiency of femtosecond laser (FSL) incision of rehydrated human donor corneas after air-drying and its effects on corneal structure.

Methods: We compared the rehydrated and fresh-preserved corneas by microscopy following Victus-Tecnolas FSL treatment for straight-edge anterior lamellar keratoplasty (ALK). The corneas were dehydrated at room temperature under a laminar-flow hood.

Results: To obtain the horizontal cut in rehydrated corneas, we increased the FSL pulse energy to 1.2 μJ from 0.80 μJ applied for the fresh corneas and obtained a clear-cut separation of the lamellar lenticule cap from the corneal bed. Light microscopy showed regular arrangement of stromal collagen lamellae, with spaces in between the fibers in the corneal stroma in the fresh and the rehydrated corneas, but the uppermost epithelial layers in the rehydrated corneas were lost. Transmission electron microscopy (TEM) revealed no signs of thermal or mechanical damage to the corneal structure. The epithelial basal membrane and Bowman's layer maintained their integrity. The epithelial basal layer and cells were separated by large spaces due to junction alteration in the rehydrated corneas. There were gaps between the lamellar layers in the stroma, especially in the rehydrated corneas. Keratocytes displayed normal structure in the fresh corneas but were devoid of microorganules in the rehydrated corneas. Minor irregularities were observed in the vertical incision and the horizontal stroma appeared smooth on scanning electron microscopy.

Conclusion: The corneal stroma of rehydrated corneas maintained morphology and integrity, while corneal cellular components were generally altered. When corneas are intended for FSL-assisted ALK, effective stromal bed incision is best achieved at a laser power higher than that currently adopted for fresh corneas.

Organ Preservation Solutions in Transplantation: A Literature Review

OBJECTIVES

Renal transplant with ABO-incompatible donors expands the donor pool. Earlier studies have focused the use of protocol biopsies in ABOincompatible transplant patients. Our study described outcomes of indication (for cause) renal biopsies and clinical outcomes in patients with ABO-incompatible renal transplant.

MATERIALS AND METHODS

This retrospective study included 164 patients from January 2012 to June 2019. Biochemical parameters, serial immunoglobulin G anti-ABO titers, and class I and II donor-specific antibody findings were obtained from hospital records, and renal graft biopsies were reviewed according to the Banff 2017 update.

RESULTS

We analyzed the results of 65 biopsies from 54 patients. Biopsy-proven acute antibody-mediated rejection (12.8%) was found to be more prevalent than acute cellular rejection (1.8%). Patients with antibodymediated rejection all had microvascular inflammation (g+ptc score of 2 or more, where g+ptc is the sum of the glomerulitis and peritubular capillaritis scores) and were positive for C4d. Acute tubular injury per se was seen in 10.3% of patients; 65% of these patients had C4d positivity in peritubular capillaries, and only 1 patient developed chronic active antibody-mediated rejection on follow-up. Patient and death-censored graft survival rates were 92% and 98% at 1 year after transplant and 88% and 91% at 3 years, respectively. Patients with an episode of antibody-mediated rejection had lower rates of patient (76.5%) and deathcensored graft survival (84.6%) at 1 year.

CONCLUSIONS

The microvascular inflammation score (g+ptc score of 2 or higher) is more reliable than diffuse C4d positivity to determine antibody-mediated rejection in ABO-incompatible transplants because diffuse C4d positivity may also be seen in etiologies unrelated to antibody-mediated rejection. Acute tubular injury with C4d positivity without microvascular injury does not confirm antibody-mediated rejection. We suggest that Banff classification be updated in ABOincompatible transplants to include diagnostic criteria for the diagnosis of antibody-mediated rejection.

Review of Gamma-Irradiated Sterile Cornea: Properties, Indications, and New Directions

ABSTRACT

Gamma-irradiated sterile cornea (GISC) is a relatively new graft tissue that follows the 30-year success of irradiation to other tissues (bone and sclera) to lessen antigenic load and infection transmission. It can serve as a graft to cover glaucoma drainage devices, as graft tissue for frank or impending corneal perforations in tectonic keratoplasty, as graft tissue in lamellar keratoplasty, and as carrier tissue for keratoprosthesis. With the limited availability of fresh corneal tissue in less developed countries, GISC may fill a need for corneal tissue worldwide. It can be used in situations where corneal endothelium is not needed and with a greatly reduced risk of rejection and infection because of the effect of irradiation on corneal tissue.

Surgeon Preference for Keratoplasty Techniques and Barriers to Performing Deep Anterior Lamellar Keratoplasty

PURPOSE

To identify barriers and facilitators to adopting deep anterior lamellar keratoplasty (DALK) for nonendothelial corneal pathology.

METHODS

An anonymous survey consisting of 22 multiple choice and free text questions was designed to gather information on demographic factors of surgeons and DALK surgical practices. The survey was emailed to members of the kera-net, a global online corneal surgeon/surgery platform.

RESULTS

A total of 100 surgeons completed the survey, most of whom practice in the United States (73%). Most surgeons (89%) reported performing DALK. Surgeons who did not learn DALK during fellowship (34%) tended to be in practice for higher numbers of years (P < 0.001). Surgeons in private practice are more likely to perform DALK versus those in other settings (92.7% vs. 80.8%, P = 0.087). Surgeons performing more corneal surgeries (at least 100 per year) are more likely to perform DALK than those who perform fewer than 100 per year (52% vs. 14%, P = 0.01). Surgeons who perform Descemet membrane endothelial keratoplasty are more likely to perform DALK than those who do not (81.7% vs. 18.3%, P = 0.014). There was also a positive correlation between PK and DALK surgical volumes (Spearman rank correlation coefficient = 0.57, P < 0.001). The main reasons for surgeon preference for DALK over PK were a desire to preserve the endothelium, intraoperative safety, and decreased complications. Longer surgical time and low patient volume were cited as barriers to adoption of DALK.

CONCLUSIONS

Alterations in DALK technique that reduce surgical time and providing more learning opportunities for DALK might improve adoption.

Glycerol-preserved corneal tissue in emergency corneal transplantation: An alternative for fresh corneal tissue in COVID-19 crisis

Purpose

Due to the COVID-19 pandemic, most of the eye banks have limited/stopped corneal collection, as this is a highly contagious disease. This has led to shortage of donor corneas worldwide. Glycerol preservation of tissue remains a viable option in this scenario. The objective is to compare fresh corneal tissue (FCT) with glycerol-preserved cornea (GPC) in emergency corneal transplantation.

Methods

This was a retrospective cohort study conducted in a tertiary care centre of Uttarakhand. Medical records of the patients who underwent therapeutic penetrating keratoplasty (TPK) were reviewed. FCT group included patients who underwent TPK with fresh corneal tissue and GPC group included patients who underwent TPK with glycerol preserved cornea. The indications and outcomes of TPK in the terms of therapeutic success were analysed and compared between both the groups.

Results

A total of 94 eyes of 91 patients underwent TPK from October 2011 to August 2017. FCT group included 60 eyes of 57 patients and GPC group included 34 eyes of 34 patients. The primary indication of TPK was infectious keratitis in both the groups (FCT-81.6%; GPC - 91.2%) There was no significant difference in the therapeutic success in both the groups (P = 0.741, Odds ratio- 1.59 with 95% CI- 0.39-6.44). Complications included glaucoma (FCT-21.7%; GPC- 35.2%) graft infection (FCT- 18.33% GPC- 2.9%); graft rejection (FCT-11.66%, GPC- 0%); and graft failure (FCT-88.33%, GPC-100%).

Conclusion

The GPC is comparable to FCTs in therapeutic transplant and can be a useful interim procedure in saving the eyes in cases of infective keratitis in the time of crisis.

A review of long-term corneal preservation techniques: Relevance and renewed interests in the COVID-19 era

The growth of eye banking in India was showing positive trends until the nation was hit by unprecedented times as a result of the COVID-19 pandemic. The impact of this has led to a downward spiraling in eye banking activities globally. Several measures had to be implemented to tide over the crisis and strategies planned for future to prepare for the needs of corneal transplantation. While eye banks in India have been practicing short- term and intermediate storage preservation media, there is a definite need to evolve other methods of very long-term preservation. This review discusses various methods of long term corneal preservation, their relevance and applications in the present times. We reviewed relevant medical literature in English from PUBMED with the key words “Corneal preservation”, “Cryopreservation”, “Glycerol preservation”, Gamma Irradiation”, “Eye Banking” ,”COVID-19”.