Effect of Cornea Preservation Time on Success of Descemet Stripping Automated Endothelial Keratoplasty: A Randomized Clinical Trial

The landscape of clinical trials in corneal regeneration: A systematic review of tissue engineering approaches in corneal disease

The limited availability of a healthy donor cornea and the incidence of allograft failure led researchers to seek other corneal substitutes via tissue engineering. Exploring the trend of clinical trials of the cornea with the vision of tissue engineering provides an opportunity to reveal future potential corneal substitutes. The results of this clinical trial are beneficial for future study designs to overcome the limitations of current therapeutic approaches. In this study, registered clinical trials of bio-based approaches were reviewed for corneal regeneration on March 22, 2024. Among the 3955 registered trials for the cornea, 392 trials were included in this study, which categorized in three main bio-based scaffolds, stem cells, and bioactive macromolecules. In addition to the acellular cornea and human amniotic membrane, several bio-based materials have been introduced as corneal substrates such as collagen, fibrin, and agarose. However, some synthetic materials have been introduced in recent studies to improve the desired properties of bio-based scaffolds for corneal substitutes. Nevertheless, new insights into corneal regenerative medicine have recently emerged from cell sheets with autologous and allogeneic cell sources. In addition, the future perspective of corneal regeneration is described through a literature review of recent experimental models.

Are For-Profit Eye Banks a Good Idea?

ABSTRACT

For-profit eye banks have been advocated because they stimulate innovation and improve the quantity and quality of corneal tissue. The claims of for-profit eye banks do not stand up to scrutiny and promote discord in the recovery and distribution field. Commercialization can adversely affect public perception of corneal donation.

Whole mount immunofluorescence analysis of fresh and stored human donor corneas highlights changes in limbal characteristics during storage

PURPOSE

Human donor corneas are an essential control tissue for corneal research. We utilized whole mount immunofluorescence (WM-IF) to evaluate how the storage affects the tissue integrity and putative limbal stem cells in human and porcine corneas. Moreover, we compare this information with the marker expression patterns observed in human pluripotent stem cell (hPSC)-derived LSCs.

METHODS

The expression of putative LSC markers was analyzed with WM-IF and the fluorescence intensity was quantified in human donor corneas stored for 1-30 days, and in porcine corneas processed 0-6 h after euthanasia. The results were compared with the staining of human and porcine corneal cryosections and with both primary and hPSC-derived LSC cultures.

RESULTS

WM-IF analyses emerged as a more effective method when compared to tissue sections for visualizing the expression of LSC markers within human and porcine corneas. Storage duration was a significant factor influencing the expression of LSC markers, as human tissues stored longer exhibited notable epithelial degeneration and lack of LSC markers. Porcine corneas replicated the expression patterns observed in fresh human tissue. We validated the diverse expression patterns of PAX6 in the limbal-corneal region, which aligned with findings from hPSC-LSC differentiation experiments.

CONCLUSIONS

WM-IF coupled with quantification of fluorescence intensities proved to be a valuable tool for investigating LSC marker expression in both human and porcine tissues ex vivo. Prolonged storage significantly influences the expression of LSC markers, underscoring the importance of fresh human or substitute control tissue when studying limbal stem cell biology.

Assessment of performance and safety of Corneal Chamber hypothermic storage medium and PSS-L corneal rinsing solution in human and porcine corneas

PURPOSE

To prove the safety and performance of the hypothermic corneal storage medium "Corneal Chamber" and the rinsing solution "PSS-L" in support of the new Conformité Européenne (CE) certification process in accordance with the Medical Device Regulation.

METHODS

Fifteen (n=15) human donor corneas and 11 (n=11) porcine corneas were evaluated for the following parameters: endothelial cell density (ECD) and mortality, percentage of hexagonal cells (HEX%), coefficient of cellular area variation (CV%) and corneal transparency at Day 0 and after 14±1 days of storage in Corneal Chamber medium at 2-8°C. Then, the same parameters were assessed after rinsing of corneas in PSS-L for 1 min at room temperature. Evaluation of gentamicin sulfate carryover after corneal storage and PSS-L rinsing was performed by ultra-high performance liquid chromatography analysis on human corneas homogenates.

RESULTS

Human and porcine corneas stored in Corneal Chamber medium showed a good overall quality of the tissue according to the quality parameters evaluated. In particular, mean ECD, HEX% and CV% did not show statistically significant changes at the end of storage and endothelial mortality increased to 3.1±3.3 and 7.8±3.5% in human and porcine corneas, respectively. Tissue rinsing with PSS-L did not affect the quality parameters evaluated before and gentamicin sulfate residues were absent in human corneas.

CONCLUSIONS

Corneal preservation in Corneal Chamber medium at 2-8°C for 14 days and the corneal rinse with PSS-L are safe and effective procedures allowing the preservation of the corneal quality parameters as well as the complete elimination of gentamicin sulfate from the tissues before transplantation.Cite Now.

Effect of Simultaneous Endothelial Keratoplasty and Cataract Surgery: A Secondary Analysis of the Descemet Endothelial Thickness Comparison Trial

PURPOSE

Combining cataract surgery with endothelial keratoplasty (triple EK) is a common practice and may be safer because it commits the patient to only one surgery. This study aimed to determine whether outcomes of pseudophakic endothelial keratoplasty and triple EK have similar outcomes.

METHODS

This was a non-prespecified secondary analysis of a multicenter, double-masked, randomized, controlled clinical trial. Enrollment centers included the Casey Eye Institute at Oregon Health and Sciences University and the Byers Eye Institute at Stanford University. Patients with damaged or diseased endothelium and were considered good candidates for either Descemet membrane endothelial keratoplasty or ultrathin Descemet stripping automated endothelial keratoplasty were randomized to one of the two surgeries 1-2 days prior to surgery. If the patient had a cataract, they underwent simultaneous cataract surgery. The primary outcome was visual acuity at 6 months. Visual acuity at 3, 12, and 24 months, 3, 6, 12, and 24 month endothelial cell density and intraoperative and postoperative complications were also recorded.

RESULTS

Those who had pseudophakic EK generally were older, more likely to be male, and more likely to have worse baseline vision with higher corneal densitometry values. After controlling for baseline visual acuity and type of keratoplasty, those that underwent Triple-EK had 0.09 better LogMAR lines better visual acuity at 6 (95% CI -0.17 to -0.10; P = 0.02) and 12 months (95% CI -0.21 to -0.07; P = 0.03). Although those receiving Triple- EK had nearly one-half LogMAR line better visual acuity at 24 months, it was no longer statistically significant (95% CI -0.20 to -0.05; P = 0.36). There was no statistically significant difference in ECD between groups at any timepoint. Those undergoing triple EK were more likely to have at least one adverse event (P = 0.02).

CONCLUSIONS

Earlier intervention with Triple-EK may improve visual acuity outcomes after endothelial keratoplasty compared with staged procedures, but may also increase the risks of adverse events including the need for re-bubble.

Comparative Proteomics Reveals Prolonged Corneal Preservation Impaired Ocular Surface Immunity Accompanied by Fibrosis in Human Stroma

Cornea transplantation is one of the most commonly performed allotransplantations worldwide. Prolonged storage of donor corneas leads to decreased endothelial cell viability, severe stromal edema, and opacification, significantly compromising the success rate of corneal transplantation. Corneal stroma, which constitutes the majority of the cornea, plays a crucial role in maintaining its shape and transparency. In this study, we conducted proteomic analysis of corneal stroma preserved in Optisol-GS medium at 4 °C for 7 or 14 days to investigate molecular changes during storage. Among 1923 identified proteins, 1634 were quantifiable and 387 were significantly regulated with longer preservation. Compared to stroma preserved for 7 days, proteins involved in ocular surface immunomodulation were largely downregulated while proteins associated with extracellular matrix reorganization and fibrosis were upregulated in those preserved for 14 days. The increase in extracellular matrix structural proteins together with upregulation of growth factor signaling implies the occurrence of stromal fibrosis, which may compromise tissue clarity and cause vision impairments. This study is the first to provide insights into how storage duration affects corneal stroma from a proteomic perspective. Our findings may contribute to future research efforts aimed at developing long-term preservation techniques and improving the quality of preserved corneas, thus maximizing their clinical application.

Graft Survival, Graft Rejection, and Glaucoma in a Consecutive Series of Descemet Stripping Endothelial Keratoplasty

PURPOSE

The goal of this study was to compare outcomes of Descemet stripping endothelial keratoplasty (DSEK) in eyes with glaucoma and abnormal anatomy to eyes with Fuchs endothelial corneal dystrophy (FECD).

METHODS

In a retrospective interventional series of all cases of DSEK between April 1, 2006, and November 30, 2015, recipient diagnosis, preoperative glaucoma status, concurrent surgical procedures, and graft outcomes were recorded. Graft survival, risk of rejection, and subsequent glaucoma surgery were estimated by using Kaplan-Meier analysis with risk factors determined by proportional hazard models.

RESULTS

Of 703 DSEKs in 666 eyes (509 subjects), the main recipient diagnoses were FECD (n = 496), pseudophakic corneal edema (n = 112), and failed graft (n = 83). Glaucoma was present in 150 cases before DSEK. Overall graft survival was 85%, 75%, and 71% at 5, 10, and 12 years, respectively, and for FECD without glaucoma was 95%, 89%, and 87% at 5, 10, and 12 years, respectively. Independent risk factors for graft failure included recipient diagnoses of pseudophakic corneal edema (HR = 8.3, P < 0.001), failed graft (HR = 6.4, P < 0.001), and preoperative medical glaucoma (HR = 7.1, P < 0.001) or surgical glaucoma (HR = 12.3, P < 0.001). Preoperative glaucoma treated by previous surgery resulted in graft survival of 28% at 10 years. Preoperative glaucoma was associated with an increased risk of graft rejection (HR = 6.8, P < 0.001) and subsequent glaucoma surgery (HR > 17.4, P < 0.001).

CONCLUSIONS

Preoperative glaucoma increases the risk of graft failure, graft rejection, and needing subsequent glaucoma surgery in the first decade after DSEK. With previous glaucoma surgery, DSEK graft survival was more favorable compared with published reports of Descemet membrane endothelial keratoplasty.

Descemet Stripping Endothelial Keratoplasty: Fifteen-Year Outcomes

PURPOSE

The purpose of this study was to evaluate 15-year outcomes of Descemet stripping endothelial keratoplasty (DSEK).

METHODS

We retrospectively reviewed an initial, consecutive series of 350 DSEK cases in 290 patients (mean age 69 years), performed between December 2003 and December 2005 for Fuchs dystrophy (86%), pseudophakic/aphakic bullous keratopathy (10%), or failed penetrating keratoplasty (4%). Outcomes included best spectacle-corrected visual acuity (BSCVA), endothelial cell density (ECD), and graft failure (defined as regraft for any reason or persistent loss of stromal clarity).

RESULTS

At 15 years, 46 of 350 DSEK grafts (13%) had failed, 155 (44%) were in patients who died, and 84 of the remaining 149 grafts (56%) were examined. After accounting for loss to follow-up, the probability of graft failure was 7% at 5 years, 16% at 10 years, and 23% at 15 years. The main risk factor for late endothelial failure was preoperative glaucoma (hazard ratio: 4.4 for medically managed and 24 for surgically managed glaucoma). The probability of an immunologic rejection episode was 7% by 1 year, 14% by 10 years, and 17% by 15 years. The median donor ECD decreased from 3030 cells/mm 2 before DSEK to 1973 cells/mm 2 at 6 months (36% loss) and 705 cells/mm 2 at 15 years (78% loss). The median BSCVA, including the eyes with ocular comorbidity, was 20/60 preoperatively, 20/40 at 3 through 12 months, and 20/30 from 2 to 15 years.

CONCLUSIONS

DSEK provided excellent long-term visual rehabilitation and graft survival in this early cohort, performed when the technique was still being refined.

Effect of Increasing Povidone-Iodine Exposure on Corneal Epithelium and Impact on Donor Rim Cultures

PURPOSE

The purpose of this study was to assess the effect of a second povidone-iodine (PVP-I) application at the time of donor tissue recovery on overall tissue quality and to analyze the rate of positive fungal and bacterial rim cultures before and after implementing increased PVP-I exposure.

METHODS

The left cornea was recovered after a single application of PVP-I, while the right cornea was recovered after double PVP-I application in research-consented donors. The epithelial cell death rate was estimated using viability assay in corneal whole mounts under 10× objective (n = 5). Clinical characteristics of epithelium, stroma, and endothelium; positive rim culture rate; and incidences of infectious postoperative adverse reactions were compared for a period of 14 months before and after implementation of increased PVP-I protocol.

RESULTS

The average epithelial cell death rate was unaltered between single and double PVP-I exposure groups. We observed a modest 10% increase in the number of tissues with mild edema after implementation of increased PVP-I exposure. Nonetheless, the percentage of tissues with moderate or severe edema was unaltered. The average positive rim culture rate decreased from 1.17% to 0.88% (P = 0.075) after implementation of the double PVP-I soak procedure. There has been only one report of infectious postoperative adverse reactions since this procedure change. By contrast, there were 5 reports for a period of 14 months before implementation of this protocol.

CONCLUSIONS

These results indicate that new donor preparation methods with an additional 5 minutes of PVP-I exposure do not affect tissue quality, reduce positive rim cultures, and lead to lower incidence of postoperative infection.

The Biologic Character of Donor Corneal Endothelial Cells Influences Endothelial Cell Density Post Successful Corneal Transplantation

Purpose

Corneal endothelial cell density (ECD) gradually decreases after corneal transplantation by unknown biologic, biophysical, or immunologic mechanism. Our purpose was to assess the association between donor corneal endothelial cell (CEC) maturity in culture and postoperative endothelial cell loss (ECL) after successful corneal transplantation.

Design

Prospective cohort study.

Participants

This cohort study was conducted at Baptist Eye Institute, Kyoto, Japan, between October 2014 and October 2016. It included 68 patients with a 36-month follow-up period who had undergone successful Descemet stripping automated endothelial keratoplasty (DSAEK) or penetrating keratoplasty.

Methods

Human CECs (HCECs) from remaining peripheral donor corneas were cultured and evaluated for maturity by surface markers (CD166⁺, CD44^-/dull, CD24^-, and CD105^-) using fluorescence-activated cell sorting. Postoperative ECD was assessed according to the mature-differentiated HCEC contents: high-maturity group: > 70%, middle-maturity group: 10% to 70%, low-maturity group: < 10%. The successful rate of ECD maintained at 1500 cells/mm² at 36 months postoperative was analyzed using the log-rank test.

Main Outcome Measures

Endothelial cell density and ECL at 36 months postoperative.

Results

The 68 included patients (mean [standard deviation] age 68.1 [13.6] years, 47.1% women, 52.9% DSAEK). The high, middle, and low-maturity groups included 17, 32, and 19 eyes, respectively. At 36 months postoperative, the mean (standard deviation) ECD significantly decreased to 911 (388) cells/mm² by 66% in the low-maturity group, compared with 1604 (436) by 40% and 1424 (613) cells/mm² by 50% in the high and middle-maturity groups (P < 0.001 and P = 0.007, respectively) and the low-maturity group significantly failed to maintain ECD at 1500 cells/mm² at 36 months postoperative (P < 0.001). Additional ECD analysis for patients who underwent DSAEK alone displayed a significant failure to maintain ECD at 1500 cells/mm² at 36 months postoperative (P < 0.001).

Conclusions

The high content of mature-differentiated HCECs expressed in culture by the donor peripheral cornea was coincident with low ECL, suggesting that a high-maturity CEC content predicts long-term graft survival. Understanding the molecular mechanism for maintaining HCEC maturity could elucidate the mechanism of ECL after corneal transplantation and aid in developing effective interventions.

Financial Disclosures

Proprietary or commercial disclosure may be found after the references.

Donor and recipient characteristics associated with rebubbling rate, endothelial cell loss, and graft failure in primary descemet membrane endothelial keratoplasty

Aim: To determine whether donor and recipient characteristics are associated with rebubbling rate, endothelial cell loss (ECL), and graft failure 3 years after primary Descemet membrane endothelial keratoplasty (DMEK). Material and Method: Records of 295 consecutive DMEK surgery and match with corresponding donor data were reviewed at a tertiary referral clinic. Recipients with intraoperative complications and coexisting ocular pathologies were excluded. Age, sex of donor and recipient, cause of donor death, death-to-preservation time (DtPT), storage time, donor endothelial cell density (ECD), and indications for surgery were analyzed for correlation with rebubbling rate, postoperative ECL, and graft failure. Further, subgroup analyses of the cause of death, donor sex, DtPT (median value, 3.5 h), and indications were performed. Multiple regression and receiver operating characteristics (ROC) analysis were used to determine the independent risk factors for graft failure. Results: This study included 114 eyes that underwent DMEK for bullous keratopathy (BK; 64%) and for Fuchs’ endothelial corneal dystrophy (FECD; 36%). The graft failure percentage was the only parameter that was higher in patients with DtPT > 3.5 h (p=0.047) than those with shorter DtPT. The probability of graft failure was seven times higher in eyes with DtPT > 3.5 h than with shorter DtPT (odds ratio 7.36, 95% confidence interval CI 1.34‒40.53) and 10 times higher in eyes with BK than those with FECD (odds ratio 10.29, 95% CI 1.01‒104.54). Conclusion:. DtPT and recipients with BK diagnosis were found to be independent risk factors for graft failure. Therefore, surgeons should consider DtPT for DMEK in eyes with BK.

Comparison of Graft Outcomes Reusing Original Intermediate-Term Cold Storage Solution for Entire Corneal Donor Storage Period With Exchanged Fresh Storage Solution After Donor Preparation in the Cornea Preservation Time Study

PURPOSE

The purpose of this study was to evaluate outcomes of Descemet stripping automated endothelial keratoplasty comparing exchange with fresh intermediate-term cold storage solution after lenticule preparation versus reuse of the original solution in the Cornea Preservation Time Study.

METHODS

In the Cornea Preservation Time Study, 508 donor corneas had lenticules prepared by the eye bank with fresh solution exchange (Fresh group) and 283 with reuse of the original solution (Original group). Storage time for all donors was ≤11 days. Graft success rates, central endothelial cell loss at 3 years, and frequency of positive donor rim cultures were compared between the 2 groups.

RESULTS

The 3-year graft success rate (95% confidence interval) was 93.4% (90.7%-95.3%) in the Fresh group and 95.2% (91.8%-97.2%) in the Original group (adjusted hazard ratio for graft failure = 0.64, 95% confidence interval, 0.33-1.24, P = 0.19). The mean percentage endothelial cell loss was significantly greater in the Fresh group versus Original group (45% ± 22% vs. 38% ± 20%, respectively, P = 0.004). Cultures were positive in 4 (1.5%) of 267 donor rims (3 fungal and 1 bacterial) in the Fresh group and in 4 (2.5%) of 158 in the Original group (P = 0.57). There were 2 postoperative infections in the Original group and none in the Fresh group.

CONCLUSIONS

The use of the original intermediate-term cold storage solution did not reduce the 3-year graft success rate compared with exchanging with fresh solution after lenticule preparation for Descemet stripping automated endothelial keratoplasty, while the frequency of positive donor rim cultures did not significantly differ between groups.

Endothelial failure and rejection in recipients of corneas from the same donor

Objective

To determine whether patients who receive corneas from the same donor have similar risks of endothelial failure and rejection.

Methods and Analysis

Patients with Fuchs endothelial dystrophy (FED) and pseudophakic bullous keratopathy (PBK) who received their first corneal transplant between 1999 and 2016 were analysed. Patients receiving corneas from donors who donated both corneas for the same indication were defined as ‘paired’. Gray’s test was used to compare the cumulative incidence of endothelial failure and rejection within 5 years post-transplant for ‘paired’ and ‘unpaired’ groups. Cox regression models were fitted to determine whether there was an association between recorded donor characteristics (endothelial cell density (ECD), age and sex and endothelial graft failure and rejection.

Results

10 838 patients were analysed of whom 1536 (14%) were paired. The unpaired group comprised 1837 (69%) recipients of single corneal donors and 7465 (69%) donors who donated both corneas for another indication. ECD was lower for unpaired single cornea donors (p<0.01). There was no significant difference in endothelial graft failure or rejection between paired and unpaired groups for FED (p=0.37, p=0.99) or PBK (p=0.88, p=0.28) nor for donor ECD, age, sex and paired donation after adjusting for transplant factors (across all models p>0.16 for ECD, p>0.32 for donor age, p>0.14 for sex match and p>0.17 for the donor effect).

Conclusion

The absence of a significant difference in graft outcome for corneal transplants for FED and PBK between paired and unpaired donors may reflect a homogeneous donor pool in the UK.

The importance of donor characteristics, post-mortem time and preservation time for use and efficacy of donated corneas for posterior lamellar keratoplasty

PURPOSE

The aim of this study is to examine whether donor age, death-to-retrieval time (DRT) and death-to-preservation time (DPT) as well as total preservation time affect donor cornea suitability for endothelial keratoplasty (EK) or penetrating keratoplasty (PK).

METHODS

A registry-based study was performed identifying 3248 corneas donated between 2011 and 2017. Data regarding donated corneas were extracted from The Danish Cornea Bank and donor medical records and evaluated for missing information. The primary outcome was whether ECD at preservation (ECD-P) or at release (ECD-R) was >2000 cells/mm² .

RESULTS

Logistic regression for ECD-P showed a significant negative effect of increasing age (OR: 1.07, 95%CI: 1.05;1.08, p < 0.001) on donor suitability. Higher ECD-P had a significant positive effect on graft eligibility (OR: 1.007 95%CI: 1.003;1.010, p < 0.001). No significant effect of donor sex (p = 0.547), DRT (p = 0.289) or DPT (p = 0.102) on donor suitability for EK or PK (Chi-squared test).

CONCLUSION

High donor age and low ECD-P negatively affect the suitability of donor corneas for EK/PK whereas DRT and DPT did not affect graft suitability.

Effect of Body Refrigeration Time on Cornea Donor Tissue

PURPOSE

To determine how early body refrigeration affects corneal donor transplant suitability and endothelial cell density.

METHODS

Donor information was obtained from the CorneaGen Eye Bank including demographics, time of death to preservation, and body refrigeration status, for donors between 2012 and 2016. The death to preservation interval was classified into 3 categories: 0 to 10, 10 to 20, and 20+ hours. Two primary logistic method models were fit using a main effects model and an interaction model to determine the association of body refrigeration on unsuitability of transplantation and endothelial cell density.

RESULTS

Analysis was from 42,929 donor eyes, with a mean (standard deviation) endothelial cell count of 2743 (415) cells/mm2. Fifty-nine percent of donor eyes were from male donors in the eye bank data set, and the mean death to preservation interval was 11.0 (5.6) hours for all eyes. Unsuitability for transplantation demonstrated a reduced adjusted odds ratio by 22% (OR = 0.78, P = 0.009) when the body was refrigerated during the death to preservation interval versus when the body was not refrigerated. Eyes that were refrigerated, however, exhibited no statistically significant difference in endothelial cell count from eyes that were not refrigerated (P = 0.12).

CONCLUSIONS

We demonstrate an appreciable effect of early body refrigeration on transplant suitability in this large cohort of eye bank eyes. There was no beneficial effect of body refrigeration on endothelial cell count.

Corneal Donation: Current Guidelines and Future Direction

PURPOSE

This review aims to outline current practices and guidelines of corneal donation and eye banking, describes the implications of COVID-19 and emerging diseases on the corneal donor pool, and discusses future trends to improve and increase the efficiency of the processes involved in corneal donation and eye banking.

SUMMARY

Corneal screening, preservation, corneal storage, and prevention of systemic disease transmission from donor to recipient have been crucial in shaping the policies of the FDA and eye banks across the world. Eye banks globally have developed varying guidelines and criteria for evaluating the viability of donor corneas. Variables such as the age of the donor, medical history, and potential disease transmission are important screening parameters. While known infectious diseases may be transmissible through the cornea, emerging infectious diseases that are not well studied may be more transmissible than other infections. In particular, coronavirus has impacted corneal transplantation as SARS-CoV-2 expression has been detected in corneal tissue and conjunctiva. In recent years, partial-thickness corneal transplantations have been introduced. Lamellar grafts and other corneal layers are now utilized for transplantation of the specific areas that are damaged.

Ubiquinol Supplementation of Donor Tissue Enhances Corneal Endothelial Cell Mitochondrial Respiration

PURPOSE

To determine whether ubiquinol improves mitochondrial function and cell viability in human donor corneal endothelial cells during hypothermic corneal tissue storage.

METHODS

Endothelial cell Descemet membrane tissues were treated with 10 μM ubiquinol, the reduced form of the antioxidant coenzyme Q10, for 5 days in Optisol-GS storage media before assaying for mitochondrial activity using extracellular flux analysis of oxygen consumption. In addition, endothelial cell Descemet membrane tissues were analyzed for cell viability using apoptosis and necrosis assays. Control tissues from mate corneas were treated with diluent only, and comparisons were analyzed for differences.

RESULTS

A total of 13 donor corneal tissues with a mean (SEM) preservation time of 11.8 days (0.4) were included for the analysis. Treatment with 10 μM ubiquinol increased spare respiratory capacity by 174% (P = 0.001), maximal respiration by 93% (P = 0.003), and proton leak by 80% (P = 0.047) compared with controls. Cells treated with ubiquinol had no significant change in cell necrosis or apoptosis.

CONCLUSIONS

Preliminary testing in donor corneal tissue at specified doses indicates that ubiquinol may be a useful biocompatible additive to hypothermic corneal storage media that increases corneal endothelial cell mitochondrial function. Additional investigations are indicated to further study and optimize the dose and formulation of ubiquinol for use in preserving donor corneal tissue function during hypothermic storage.

Donor DMEK Tissue Characteristics: Association With Rebubble Rate and 6-Month Endothelial Cell Loss

PURPOSE

To determine whether specific donor characteristics influence postoperative rebubble rate and 6-month endothelial cell loss (ECL) in Descemet membrane endothelial keratoplasty (DMEK).

METHODS

A retrospective analysis of a consecutive series of 857 DMEK surgeries using eye bank-prepared donor tissue was performed between September 2013 and April 2018. DMEK graft characteristics including donor age, preoperative endothelial cell density (ECD), preservation time, death-to-preservation time, and donor diabetes status were analyzed for correlation with rebubble rate and 6-month postoperative ECL. Subgroup analyses of donor age, preoperative ECD, preservation time, death-to-preservation time, preparation-to-surgery time, and diabetes severity were also performed. Statistically significant relationships between donor characteristics and rebubble rate or 6-month postoperative ECL were determined using Pearson correlation, one-way analysis of variance, t test, and χ analysis.

RESULTS

The overall rate of rebubble after 857 surgeries performed by 7 surgeons during the study period was 12.6%. There was no significant relationship between postoperative rebubble rate and donor age, preoperative ECD, preservation time, death-to-preservation time, preparation-to-surgery time, or donor diabetes status. The subgroup analysis of these characteristics also yielded no significant relationship with rebubble rate. There was also no significant relationship between 6-month postoperative ECL and analyzed donor factors.

CONCLUSIONS

Donor characteristics such as higher donor age, lower preoperative ECD (<2500), longer preservation time, and donor diabetes did not increase the rebubble rate or the 6-month ECL after DMEK. These results indicate that common surgeon preferences for donor tissues that are younger, fresher, with higher cell count, and without diabetes do not translate into superior postsurgical outcomes.

Solubilized ubiquinol for preserving corneal function

Defective cellular metabolism, impaired mitochondrial function, and increased cell death are major problems that adversely affect donor tissues during hypothermic preservation prior to transplantation. These problems are thought to arise from accumulated reactive oxygen species (ROS) inside cells. Oxidative stress acting on the cells of organs and tissues preserved in hypothermic conditions before surgery, as is the case for cornea transplantation, is thought to be a major reason behind cell death prior to surgery and decreased graft survival after transplantation. We have recently discovered that ubiquinol - the reduced and active form of coenzyme Q10 and a powerful antioxidant - significantly enhances mitochondrial function and reduces apoptosis in human donor corneal endothelial cells. However, ubiquinol is highly lipophilic, underscoring the need for an aqueous-based formulation of this molecule. Herein, we report a highly dispersible and stable formulation comprising a complex of ubiquinol and gamma cyclodextrin (γ-CD) for use in aqueous-phase ophthalmic products. Docking studies showed that γ-CD has the strongest binding affinity with ubiquinol compared to α- or β-CD. Complexed ubiquinol showed significantly higher stability compared to free ubiquinol in different aqueous ophthalmic products including Optisol-GS® corneal storage medium, balanced salt solution for intraocular irrigation, and topical Refresh® artificial tear eye drops. Greater ROS scavenging activity was noted in a cell model with high basal metabolism and ROS generation (A549) and in HCEC-B4G12 human corneal endothelial cells after treatment with ubiquinol/γ-CD compared to free ubiquinol. Furthermore, complexed ubiquinol was more effective at lowering ROS, and at far lower concentrations, compared to free ubiquinol. Complexed ubiquinol inhibited lipid peroxidation and protected HCEC-B4G12 cells against erastin-induced ferroptosis. No evidence of cellular toxicity was detected in HCEC-B4G12 cells after treatment with complexed ubiquinol. Using a vertical diffusion system, a topically applied inclusion complex of γ-CD and a lipophilic dye (coumarin-6) demonstrated transcorneal penetrance in porcine corneas and the capacity for the γ-CD vehicle to deliver drug to the corneal endothelium. Using the same model, topically applied ubiquinol/γ-CD complex penetrated the entire thickness of human donor corneas with markedly greater ubiquinol retention in the endothelium compared to free ubiquinol. Lastly, the penetrance of ubiquinol/γ-CD complex was assayed using human donor corneas preserved for 7 days in Optisol-GS® per standard industry practices, and demonstrated higher amounts of ubiquinol retained in the corneal endothelium compared to free ubiquinol. In summary, ubiquinol complexed with γ-CD is a highly stable composition that can be incorporated into a variety of aqueous-phase products for ophthalmic use including donor corneal storage media and topical eye drops to scavenge ROS and protect corneal endothelial cells against oxidative damage.

Endothelial Keratoplasty Update 2020

ABSTRACT

Endothelial keratoplasty has revolutionized the treatment of corneal endothelial dysfunction and lowered the threshold for treatment by providing rapid visual rehabilitation and setting a high standard for safety and efficacy. Over time, endothelial keratoplasty techniques have evolved toward the use of thinner tissue to optimize visual outcomes; refinements have facilitated donor tissue preparation, handling, and attachment; and adaptations have expanded utilization in eyes with challenging ocular anatomy. Despite early concerns about graft longevity, emerging 10-year endothelial cell loss and graft survival data have been encouraging. A shortage of human donor corneas restricts utilization in many areas of the world and is driving a search for keratoplasty alternatives. Further work is needed to expand the donor supply, minimize impediments to adoption, optimize graft survival, and improve refractive predictability.

Random Survival Forests Analysis of Intraoperative Complications as Predictors of Descemet Stripping Automated Endothelial Keratoplasty Graft Failure in the Cornea Preservation Time Study

Importance

A new analytic method can evaluate factors of interest associated with graft failure after Descemet stripping automated endothelial keratoplasty (DSAEK) or more generally in any ophthalmic surgical setting with a time-to-event outcome.

Objective

To reanalyze types of intraoperative complications associated with DSAEK graft failure in the Cornea Preservation Time Study using random survival forests.

Design, Setting, and Participants

This cohort study, initially conceived in April 2019, used a prediction model to conduct a post hoc secondary analysis of data collected in a multicenter, double-masked, randomized clinical trial. Forty US clinical sites with 70 surgeons participated, with donor corneas provided by 23 US eye banks. The study included 1090 participants, representing 1330 eyes, undergoing DSAEK for Fuchs dystrophy (1255 eyes [94.4%]) or pseudophakic or aphakic corneal edema (75 eyes [5.6%]). Enrollment occurred between April 16, 2012, and February 20, 2014, and follow-up ended June 5, 2017. Statistical analysis was performed from July 10, 2019, to May 29, 2020.

Intervention

Descemet stripping automated endothelial keratoplasty with random assignment of a donor cornea with preservation time of 7 days or less or 8 to 14 days.

Main Outcomes and Measures

Ranked variable importance for intraoperative complications among 50 donor, recipient, and eye bank variables and restricted mean survival time through 47 months (1434 days) after DSAEK were examined. Random survival forests, a nonparametric method (with less restrictive model assumptions) that is far more flexible in its ability to model nonlinear effects and interactions, was used to analyze the data.

Results

This study included 1090 participants (663 women [60.8%]; median age, 70 years [range, 42-90 years]), representing 1330 eyes. Random survival forests ranked a DSAEK intraoperative complication as the third most predictive factor of graft failure, after surgeon and eye bank, in the final model with 5 predictors. In the first 47 months after DSAEK, the estimated mean difference in restricted mean survival time for grafts that experienced a DSAEK intraoperative complication vs those that did not was -227 days (99% CI, -352 to -70 days) based on the final RSF model.

Conclusions and Relevance

These findings, while post hoc, support the hypothesis that random survival forests allow for an improved analytic approach for identifying factors predictive of graft failure and for obtaining adjusted graft survival estimates. Random survival forests offer the opportunity to guide the development of future population-based cohort ophthalmic surgical studies, establishing definitive factors for procedural success.

Corneal endothelial cell therapy: feasibility of cell culture from corneas stored in organ culture

In 2013, a clinical trial was initiated to investigate cell therapy for the treatment of corneal endothelial decompensation. Cultivating human corneal endothelial cells (CECs) while maintaining their functional phenotype is challenging; therefore, establishment of a confirmed protocol is pivotal for obtaining approval from regulatory authorities for use of cellular therapy products. In this study, we evaluated organ culture (OC) as a storage method for donor corneas used as a raw material for establishing CEC cultures. OC allows storage of corneal tissue for conventional corneal transplantation at 31-37 °C for up to 5 weeks, whereas storage at 4 °C is limited to 2 weeks. We investigated 20 pairs of corneas: one cornea of each pair was stored in OC and the other in cold storage for one week before CEC culture. In 15/20 cases, the CECs assumed a hexagonal sheet-like monolayer structure and expressed endothelial function-related markers. CECs were also obtained from OC corneas that had been stored for 1 (n = 19) and 2 (n = 7) months. As a further test, CECs were cultivated from 5 OC corneas that had been transported from France to Japan. In all cases, these corneas, even after international transport, generated CECs that formed hexagonal monolayers with clinically applicable and sufficiently high cell densities. In conclusion, the CEC cultures required for endothelial cell therapy can be obtained from OC corneas without changing the standard storage operating procedures of the eye banks.

Translational and Regulatory Challenges of Corneal Endothelial Cell Therapy: A Global Perspective

Cell therapies are emerging as a unique class of clinical therapeutics in medicine. In 2015, Holoclar (ex vivo expanded autologous human corneal epithelial cells containing stem cells) gained the regulatory approval for treating limbal stem cell deficiency after chemical eye burn. This has set a precedent in ophthalmology and in medicine, reinforcing the therapeutic promise of cell therapy. However, to generalize and commercialize cell therapies on a global scale, stringent translational and regulatory requirements need to be fulfilled at both local and international levels. Over the past decade, the Singapore group has taken significant steps in developing human corneal endothelial cell (HCEnC) therapy for treating corneal endothelial diseases, which are currently the leading indication for corneal transplantation in many countries. Successful development of HCEnC therapy may serve as a novel solution to the current global shortage of donor corneas. Based on the experience in Singapore, this review aims to provide a global perspective on the translational and regulatory challenges for bench-to-bedside translation of cell therapy. Specifically, we discussed about the characterization of the critical quality attributes (CQA), the challenges that can affect the CQA, and the variations in the regulatory framework embedded within different regions, including Singapore, Europe, and the United States. Impact statement Functional corneal endothelium is critical to normal vision. Corneal endothelial disease-secondary to trauma, surgery, or pathology-represents an important cause of visual impairment and blindness in both developed and developing countries. Currently, corneal transplantation serves as the current gold standard for treating visually significant corneal endothelial diseases, although limited by the shortage of donor corneas. Over the past decade, human corneal endothelial cell therapy has emerged as a promising treatment option for treating corneal endothelial diseases. To allow widespread application of this therapy, significant regulatory challenges will need to be systematically overcome.

A simple empirical inventory model for managing the processed corneal tissue equitably in hospitals with demand differentiation

This paper peruses one of the most challenging healthcare concerns related to human organ transplantation. In this regard, a medical system’s health-economic objectives are investigated to (1) achieve a desirable level of health equity in offering healthcare services to patients who are differentiated in terms of medical conditions, and (2) minimize total costs incurred across managing the inventory. This paper presents the first-ever operational research study to manage processed corneal tissue (PCT). Besides, hybrid demand-oriented policies have been proposed to equitably issue and assign specific inventories to demands with distinct medical urgent levels (ULs). In this regard, a practical multi-objective mixed-integer linear programming (MOMILP) model is proposed for a system with multiple products that can be substituted with each other according to medical priorities. A goal programming (GP) approach is utilized to find the optimum solution. The applicability of the model is validated through a real case study. Finally, several sensitivity analyses are conducted to examine the effect of critical parameters on the solutions to gain useful managerial insights. The results show that the proposed health-economic trade-off is well performed and can efficiently handle the real case.

Factors influencing endothelial cell density of corneas for transplantation

To evaluate factors affecting corneal endothelial cell density (ECD) under enucleation and preservation time studies at Eye Bank of the Federal District of Brazil. We conducted a case-control study collecting data from 1128 corneas where death-to-enucleation time and enucleation-to-preservation time were within 24 h. Low cell count were those corneas with an ECD less than 2000 cells/mm² and high cell count was defined as those with ECD greater than 2000 cells/mm². We calculated the independent risk factors related to: cause of death, donor age, death-to-enucleation time, enucleation-to-preservation time and primary graft failure. Correlation analysis was used to assess which parameters influence ECD: death-to-enucleation time, enucleation-to-preservation time, average cell area (AVE), coefficient of variation and percentage of hexagonal cells. Of the total number of corneas, 1004 had ECD data and were selected for the study. 87.4% (n = 877) had high cell counts with 2699 ± 412 cells/mm². The mean donor age was 38.8 ± 16 years. The most common causes of death were external causes (48.6%, n = 488). Longer times from death-to-enucleation, up to 24 h were not associated with a decrease in ECD (OR 0.58; P = 0.44) or risk of graft survival (P = 0.74). Enucleation-to-preservation intervals greater than 12 h showed increased risk of graft survival (P = 0.04). AVE was the main parameter for ECD (R² = 0.96, P < 0.001). The overall graft survival rate was 98.2% (n = 761). Donors with 40 years of age and above did not present a higher risk of graft survival (P = 0.09). We suggest that the maximum time from death-to-enucleation should be 24 h, assuming the body has been refrigerated after 6 h; and from enucleation-to-preservation time of 12 h, followed by proper processing and cornea morphology examination.

Corneal transplantation after failed grafts: Options and outcomes

Corneal transplantation is the most commonly performed human tissue transplantation procedure worldwide. Because of the large number of transplants, corneal graft failure has become one of the most common indications for corneal transplantation. The relatively recently developed lamellar transplant techniques have brought about specific potential complications leading to graft failure that may require different approaches to repeat transplantation other than penetrating keratoplasty. On the other hand, these new lamellar techniques also provide novel ways of rescuing failed penetrating grafts, with potential advantages over successive penetrating keratoplasties, such as reduced intraoperative risks and faster visual rehabilitation. We summarize the incidence and risk factors of graft failure for penetrating and lamellar (stromal and endothelial) corneal transplants and discuss the various surgical alternatives currently available to rescue such failed grafts, with a focus on the reported outcomes and limitations.

Three-month Storage of Human Corneas in an Active Storage Machine

BACKGROUND

Corneal storage for the very long term, without degradation, would make it possible to optimize a very limited resource worldwide. We previously demonstrated the superiority, compared to conventional 4-week passive organ culture (OC), of an active storage machine (ASM) that restores intraocular pressure and medium renewal. Here, we investigate eye banking for up to 3 months.

METHODS

In a randomized preclinical trial with 24 paired corneas, 1 was stored in OC and the other in ASM, using the same medium. Assessments were done on the second day and at 3 months: endothelial cell density (ECD in cells/mm), corneal transparency and thickness. At day 86, OC corneas were deswelled in a common hyperosmotic medium, but not the ASM corneas, which had remained thin. In addition, at day 88, viable ECD was measured using a live/dead assay, and endothelial expression of Na/K ATPase, Cox IV, ZO-1, N-CAM, and CD166 was observed.

RESULTS

The ASM extended storage to 3 months with unprecedented endothelial cell quality: no OC corneas remained suitable for transplantation, but one-third of ASM corneas were compliant (ECD > 2000/mm). Given that corneas with ECD > 1600/mm were also usable for emergency, 58% of ASM corneas were usable versus 33% in OC. EC survival was 53% higher in ASM (P < 0.001), structural and functional proteins of ECs were much better preserved in ASM, and it prevented the constant major edema of OC.

CONCLUSIONS

By extending graft survival to 3 months, the ASM will optimize eye banking and open up new perspectives in experimental research.

Corneal endothelial dysfunction: Evolving understanding and treatment options

The cornea is exquisitely designed to protect the eye while transmitting and focusing incoming light. Precise control of corneal hydration by the endothelial cell layer that lines the inner surface of the cornea is required for optimal transparency, and endothelial dysfunction or damage can result in corneal edema and visual impairment. Advances in corneal transplantation now allow selective replacement of dysfunctional corneal endothelium, providing rapid visual rehabilitation. A series of technique improvements have minimized complications and various adaptations allow use even in eyes with complicated anatomy. While selective endothelial keratoplasty sets a very high standard for safety and efficacy, a shortage of donor corneas in many parts of the world restricts access, prompting a search for alternatives. Clinical trials are underway to evaluate the potential for self-recovery after removal of dysfunctional central endothelium in patients with healthy peripheral endothelium. Various approaches to using cultured human corneal endothelial cells are also in clinical trials; these aim to multiply cells from a single donor cornea for use in potentially hundreds of patients. Pre-clinical studies are underway with induced pluripotent stem cells, endothelial stem cell regeneration, gene therapy, anti-sense oligonucleotides, and various biologic/pharmacologic approaches designed to treat, prevent, or retard corneal endothelial dysfunction. The availability of more therapeutic options will hopefully expand access around the world while also allowing treatment to be more precisely tailored to each individual patient.

Optimisation of Storage and Transportation Conditions of Cultured Corneal Endothelial Cells for Cell Replacement Therapy

As the cornea is one of the most transplanted tissues in the body it has placed a burden on the provision of corneas from cadaveric donors. Corneal endothelial dysfunction is the leading indication for cornea transplant. Therefore, tissue engineering is emerging as an alternative approach to overcome the global shortage of transplant-grade corneas. The propagation and expansion of corneal endothelial cells has been widely reported. However, one obstacle to overcome is the transport and storage of corneal endothelial cells. In this study we investigated whether tissue engineered corneal endothelial cells can be preserved in hypothermic conditions. Human corneal endothelial cells (HCEnCs) were exposed to various temperatures (4 °C, 23 °C, and 37 °C) in both adherent and suspension storage models. Optimal storage media and storage duration was tested along with post-storage viability. Following storage and subsequent recovery at 37 °C, cell phenotype was assessed by immunofluorescence, gene and protein expression, and proliferative capacity analysis. Functionality was also assessed within a rabbit model of bullous keratopathy. Our data support our hypothesis that functional HCEnCs can be preserved in hypothermic conditions.

Proposed risk factors for failure of transplanted eye bank-prepared descemet stripping automated endothelial keratoplasty tissues

To investigate the possible risk factors for failure of transplanted eye bank-prepared Descemet stripping automated endothelial keratoplasty (DSAEK) tissues. In a retrospective study between March 2011 and March 2019, all the failed DSAEK cases (131 cases) reported to the Central Eye Bank of Iran were compared with a surgeon-matched successful DSAEK group (control, 126 cases) in terms of the donor, DSAEK tissue, and recipient characteristics. Univariate analysis indicated that the DSAEK tissue preparation from excised corneoscleral tissues (OR 2.17; P = 0.026) and donor conjunctival hyperemia (OR 1.62; P = 0.042) were more common in the re-DSAEK group than in the controls. Other donor and recipient characteristics as well as other DSAEK tissue criteria were not significantly different between the re-DSAEK and control groups. DSAEK lenticules in both re-DSAEK and control groups demonstrated symmetric contours. Subgroup analyses in the re-DSAEK group revealed a higher rate of surgeons' low to moderate experience in comparison to those of high experience (P < 0.001). Additionally, failed DSAEK was observed more commonly in donors aged over 50 years than among those under 30 years (P < 0.001). Our study showed that DSAEK tissues prepared from excised corneoscleral tissues and from donors with conjunctival hyperemia were associated with higher rates of re-DSAEK due to failed DSAEK. An increasing trend of re-DSAEK was observed with shorter surgeons' experience and more advanced donor's age.

Discrepancies in Endothelial Cell Density Values of Human Donor Corneas Resulting From Comparison Between Specular Microscopes and Endothelial Analysis Methods

PURPOSE

The methods for specular microscopy evaluation across eye banks differ, which may result in variability in endothelial cell density (ECD) values that influence the surgeon's decision about donor tissue. A comparison of instruments and analysis methods is conducted in this study.

METHODS

Specular images were captured from 97 donor corneas using both HAI and Konan specular microscopes. A single best quality image of each cornea from each instrument was graded using the respective inherent software and analysis method (HAI: variable frame method; Konan: center method). All raw specular images were standardized for dimensions and regraded in the CellChek system in a blinded fashion. The grading variances and paired t test were performed between instruments in both inherent and standardized analyses. Correlation and Bland-Altman analyses between instruments were also performed.

RESULTS

Using the software inherent within HAI and Konan, the mean ECD readings for the 97 corneas were 2764 ± 583 and 2605 ± 517 cell/mm (P = 0.045), respectively, with a variance of 8.05% (range 0.26%-27.2%). HAI resulted in a higher ECD value in 79 corneas (81.4%). In CellChek software analysis, the mean ECD readings did not differ (2609 ± 514 and 2496 ± 507 cells/mm, respectively, P = 0.127), with a variance of 5.6% (range 0.24%-19.8%).

CONCLUSIONS

There is a slight statistically significant mean difference between the ECD values obtained from the 2 specular microscopes, which is negated by standardization to a single analysis method. Eye banks and surgeons should use caution in making decisions based only on very small differences in ECD between otherwise equivalent corneal donor tissues.

Towards Clinical Trials in Fuchs Endothelial Corneal Dystrophy: Classification and Outcome Measures-The Bowman Club Lecture 2019

The surgical treatment of Fuchs endothelial corneal dystrophy (FECD) has advanced dramatically over the last two decades. Penetrating keratoplasty has been superseded by various iterations of endothelial keratoplasty, and currently, surgical removal of host Descemet membrane without keratoplasty is being investigated. These surgical advances have been accompanied by significant improvement of our understanding of the underlying disease mechanisms, not least the discovery that FECD in western populations is predominantly an intronic trinucleotide repeat expansion disorder in the transcription factor 4 gene that results in RNA toxicity and mis-splicing. Understanding the disease mechanisms augurs well for developing targeted molecular medical therapies, which will require careful clinical investigation through trials to prove their efficacy and safety. As the field advances towards clinical trials, investigators should carefully define the disease state being treated and consider the options for outcome measures relevant to the type of intervention. FECD, and the outcomes of interventions to treat the disease, can be measured in terms of corneal morphology, corneal function and clinical impact. Standardising the approach for defining FECD and careful thought about the outcomes of intervention that are reported will help make the results of future trials for FECD applicable in clinical practice.

Effect of Graft Attachment Status and Intraocular Pressure on Descemet Stripping Automated Endothelial Keratoplasty Outcomes in the Cornea Preservation Time Study

PURPOSE

To examine the association of donor, recipient, and operative factors on graft dislocation after Descemet stripping automated endothelial keratoplasty (DSAEK) in the Cornea Preservation Time Study (CPTS) as well as the effects of graft dislocation and elevated IOP on graft success and endothelial cell density (ECD) 3 years postoperatively.

DESIGN

Cohort study within a multi-center, double-masked, randomized clinical trial.

METHODS

1090 individuals (1330 study eyes), median age 70 years, undergoing DSAEK for Fuchs endothelial corneal dystrophy (94% of eyes) or pseudophakic or aphakic corneal edema (6% of eyes). Recipient eyes receiving donor corneal tissue randomized by preservation time (PT) of 0-7 days (N = 675) or 8-14 days (N = 655) were monitored for early or late graft failure through 3 years. Donor, recipient, operative, and postoperative parameters were recorded including graft dislocation (GD), partial detachment, and pre- and post-operative IOP. Pre- and postoperative central donor ECD were determined by a central image analysis reading center. Proportional hazards, mixed effects, and logistic regression models estimated risk ratios and (99% confidence intervals).

RESULTS

Three independent predictive factors for GD were identified: a history of donor diabetes (odds ratio [OR]: 2.29 [1.30, 4.02]), increased pre-lamellar dissection central corneal thickness (OR: 1.13 [1.01, 1.27] per 25µ increase), and operative complications (OR: 2.97 [1.24, 7.11]). Among 104 (8%) eyes with GD, 30 (28.9%) developed primary donor or early failure and 5 (4.8%) developed late failure vs. 15 (1.2%; P < .001) and 29 (2.4%; P = .04), respectively, of 1226 eyes without GD. 24 (2%) of 1330 study eyes had early acutely elevated postoperative IOP that was associated with a higher risk of graft failure through 3 years (hazard ratio: 3.42 [1.01, 11.53]), but not with a lower mean 3-year ECD (mean difference 61 (-479, 601) cells/mm², P = .77). History of elevated postoperative IOP beyond 1 month was not significantly associated with 3-year graft success or ECD.

CONCLUSIONS

Donor diabetes, increased donor corneal thickness, and intraoperative complications were associated with an increased risk of GD. Early acutely elevated postoperative IOP and GD significantly increased the risk for graft failure following DSAEK.

Corneal Endothelial Cell Loss 3 Years After Successful Descemet Stripping Automated Endothelial Keratoplasty in the Cornea Preservation Time Study: A Randomized Clinical Trial

Importance

Demonstrating that endothelial cell loss following Descemet stripping automated endothelial keratoplasty (DSAEK) is independent of donor cornea preservation time (PT) could increase the pool of corneal tissue available for keratoplasty.

Objective

To determine whether endothelial cell loss 3 years after successful DSAEK is related to PT.

Design, Setting, and Participants

A multicenter, double-masked, randomized clinical trial included 40 clinical sites (70 surgeons) in the United States, with donor corneas provided by 23 US eye banks. A total of 945 eyes of 769 participants were included in the Cornea Preservation Time Study that had not experienced graft failure 3 years after DSAEK, performed primarily for Fuchs endothelial corneal dystrophy (96% of the cohort). The study was conducted from April 16, 2012, to June 5, 2017.

Interventions

DSAEK with random assignment of a donor cornea with PT of 0 to 7 days (0-7d PT) or 8 to 14 days (8-14d PT).

Main Outcomes and Measures

Endothelial cell density (ECD) at 3 years determined by a central image analysis reading center from clinical specular or confocal central endothelial images.

Results

Nine hundred forty-five eyes of 769 participants (median age, 70 years [range, 42-90 years], 60.8% women, 93.0% white) in the Cornea Preservation Time Study that had not experienced graft failure 3 years after DSAEK were included. At the initial eye bank tissue screening, mean (SD) central ECD was 2746 (297) cells/mm2 in the 0-7d PT group (n = 485) and 2723 (284) cells/mm2 in the 8-14d PT group (n = 460). At 3 years, the mean (SD) ECD decreased from baseline by 37% (21%) in the 0-7d PT group and 40% (22%) in the 8-14d PT group to 1722 (626) cells/mm2 and 1642 (631) cells/mm2, respectively (mean difference, 73 cells/mm2; 95% CI, 8-138 cells/mm2; P = .03). When analyzed as a continuous variable (days), longer PT was associated with lower ECD (mean difference by days, 15 cells/mm2; 95% CI, 4-26 cells/mm2; P = .006). Endothelial cell loss (ECL) was comparable from 4 to 13 days’ PT (n = 878; 36%-43% when tabulated by day). Available extension study ECD results at 4 years mirrored those at 3 years in the 203 eyes in the 0-7d PT group (mean [SD] ECD, 1620 [673] cells/mm2 and mean [SD] ECL, 41% [23%]) and 209 eyes in the 8-14d PT group (mean [SD] ECD, 1537 [683] cells/mm2 and mean [SD] ECL, 44% [23%]) (mean difference, 112 cells/mm2; 95% CI, 5-219 cells/mm2; P = .04).

Conclusions and Relevance

Although ECL 3 years after Descemet stripping automated endothelial keratoplasty is greater with longer PT, the effect of PT on ECL is comparable from 4 to 13 days’ PT.

Adhesion Strength and Rolling Properties of Descemet Membrane Endothelial Keratoplasty Grafts in a Rabbit Eye Model

Purpose: To investigate the optimal time for Descemet membrane endothelial keratoplasty (DMEK) graft peeling, and to analyze the rolling properties of endothelial denuded grafts in a rabbit eye model. Materials and Methods: The vertical peeling force required to peel 1 mm wide Descemet membrane (DM) strips, was measured as the change in weight of the system during force application in a rabbit model. Twenty-one rabbit corneoscleral rims were stored in phosphate-buffered saline (PBS) at 4°C, and force analysis was performed at days 1, 5, or 21 after harvesting. After half of the strips of day 5 corneas were peeled and analyzed, the rims were moved to Optisol GS at 4°C, and the remaining strips were peeled off for force analysis at day 10. Separate DM grafts (n = 7) were analyzed by intraoperative optical coherence tomography (OCT) to determine the tissue rolling diameter before and after removal of endothelial cells by a swab. Unpaired t-test was used for statistical analysis. Results: There was a decrease in DM peeling force (p = .008) between days 1 and 5 (556.04 ± 111.76 and 324.30 ± 96.4 mg, respectively), and no difference between days 5 and 21 (p = .53). Peeling force for day 5 corneas placed in Optisol was higher at day 10 (324.30 ± 96.4 to 669.92 ± 166.24 mg, p = .005). The average rolling diameter of DM grafts was similar before and after the removal of endothelial cells (257.9 ± 131.1 and 249.8 ± 126.6 μm, respectively). Conclusions: DMEK Graft procurement could be potentially facilitated by lower DM-stromal adhesion strength at day five after obtaining corneoscleral rims, in a rabbit eye model. Time in the storage medium may influence adhesion strength. Endothelial cells do not appear to play a significant role in the rolling diameter of DM grafts.

Postoperative Endothelial Cell Density Is Associated with Late Endothelial Graft Failure after Descemet Stripping Automated Endothelial Keratoplasty

PURPOSE

To determine whether preoperative endothelial cell density (ECD) and postoperative ECD after Descemet stripping automated endothelial keratoplasty (DSAEK) are associated with late endothelial graft failure (LEGF) in the Cornea Preservation Time Study (CPTS).

DESIGN

Cohort study within a multicenter, randomized clinical trial.

PARTICIPANTS

A total of 1007 individuals (1223 study eyes), mean age 70 years, undergoing DSAEK for Fuchs' dystrophy (94% of eyes) or pseudophakic or aphakic corneal edema (PACE) (6% of eyes) and followed for up to 5 years.

METHODS

Central ECD was determined by a central image analysis reading center. Preoperative ECD was determined for 1209 eyes that did not fail and 14 eyes that experienced LEGF. The ECD at 6 and 12 months after DSAEK, the change in ECD from preoperative to 6 and 12 months, surgeon-reported operative complications, and postoperative graft dislocation were investigated for an association with LEGFs unrelated to other postoperative events. Univariable and multivariable Cox proportional hazards regression models were used to assess associations.

MAIN OUTCOME MEASURES

Late endothelial graft failure and its associations with pre- and postoperative ECD and operative complications.

RESULTS

The cumulative probability of LEGF was 1.3% (95% confidence interval [CI], 0.8%-2.4%). Median (interquartile range [IQR]) preoperative ECDs were similar for eyes with LEGF (2523; 2367-3161) cells/mm²) and eyes without failure (2727; 2508-2973) cells/mm²) (P = 0.34). The ECD at 6 months was associated with LEGF (P < 0.001) in time-to-event analyses, whereas preoperative ECD was not (P = 0.55). The cumulative incidence (95% CI) of LEGF was 6.5% (3.0%, 14.0%) for 97 grafts with a 6-month ECD less than 1200 cells/mm², 0.3% (0.0%, 2.4%) for 310 grafts with a 6-month ECD between 1200 and 2000 cells/mm², and 0.6% (0.1%, 2.7%) for 589 grafts with a 6-month ECD greater than 2000 cells/mm². In multivariable analyses, ECD at 6 months and operative complications were both associated with LEGF (P = 0.002 and P = 0.01, respectively), whereas graft dislocation was not (P = 0.61).

CONCLUSIONS

In eyes undergoing DSAEK, preoperative ECD is unrelated to LEGF, whereas lower ECD at 6 months is associated with LEGF. Early endothelial cell loss after DSAEK and intraoperative complications should be minimized to improve graft survival.

Donor, Recipient, and Operative Factors Associated With Increased Endothelial Cell Loss in the Cornea Preservation Time Study

Importance

Determining factors associated with endothelial cell loss after Descemet stripping automated endothelial keratoplasty (DSAEK) could improve long-term graft survival.

Objective

To evaluate the associations of donor, recipient, and operative factors with endothelial cell density (ECD) 3 years after DSAEK in the Cornea Preservation Time Study.

Design, Setting, and Participants

This cohort study was a secondary analysis of data collected in a multicenter, double-masked, randomized clinical trial. Forty US clinical sites with 70 surgeons participated, with donor corneas provided by 23 US eye banks. Individuals undergoing DSAEK for Fuchs dystrophy or pseudophakic/aphakic corneal edema were included.

Interventions

The DSAEK procedure, with random assignment of a donor cornea with a preservation time of 0 to 7 days or 8 to 14 days.

Main Outcomes and Measures

Endothelial cell density at 3 years as determined by a reading center from eye bank and clinical specular or confocal central endothelial images.

Results

The study included 1090 participants (median age, 70 years) with 1330 affected eyes (240 bilateral cases [22.0%]), who underwent DSAEK for Fuchs dystrophy (1255 eyes [94.4%]) or pseudophakic/aphakic corneal edema (PACE) (75 eyes [5.6%]). Of these, 801 eyes (60.2%) belonged to women and 1207 (90.8%) to white individuals. A total of 749 participants (913 eyes; 164 [21.9%] bilateral cases) had functioning grafts with acceptable endothelial images preoperatively and at 3 years postoperatively and were included in this analysis. Factors associated with a lower ECD at 3 years (estimated effect with 99% CI) in the final multivariable model included donors with diabetes (-103 [-196 to -9] cells/mm2), lower screening ECD (-234 [-331 to -137] per 500 cells/mm2), recipient diagnosis of PACE (-257 [-483 to -31] in cells/mm2), and operative complications (-324 [-516 to -133] in cells/mm2). Endothelial cell loss (ECL) from a preoperative measurement to a 3-year postoperative measurement was 47% (99% CI, 42%-52%) for participants receiving tissue from donors with diabetes vs 43% (99% CI, 39%-48%) without diabetes; it was 53% (99% CI, 44%-62%) for participants diagnosed with PACE vs 44% (99% CI, 39%-49%) for those diagnosed with Fuchs dystrophy, and 55% (99% CI, 48%-63%) in participants who experienced operative complications vs 44% (99% CI, 39%-48%) in those who did not. No other donor, recipient, or operative factors were significantly associated with 3-year ECD.

Conclusions and Relevance

Donor diabetes, lower screening ECD, a PACE diagnosis in the recipient, and operative complications were associated with lower ECD at 3 years after DSAEK surgery and may be associated with long-term graft success. While causation cannot be inferred, further studies on the association of donor diabetes and PACE in recipients with lower 3-year ECD warrant further study.

Factors Associated With Graft Rejection in the Cornea Preservation Time Study

PURPOSE

To identify factors related to graft rejection following Descemet stripping automated endothelial keratoplasty (DSAEK) in the Cornea Preservation Time Study (CPTS).

DESIGN

Cohort study within a multicenter randomized clinical trial.

METHODS

A total of 1330 eyes of 1090 subjects undergoing DSAEK were randomized to receive a donor cornea with preservation time (PT) of 0-7 days (n = 675) or 8-14 days (n = 655) and followed for 3 years. Central endothelial cell density (ECD) was determined by a central image analysis reading center. Multivariable Cox models adjusted for PT, recipient diagnosis, and surgeon effect were used to identify factors associated with rejection.

RESULTS

Cumulative probability of definite graft rejection was 3.6% (99% confidence interval 2.5%-5.3%). Younger recipient age was associated with graft rejection (P < .001; hazard ratio: 0.53 [0.33, 0.83] per decade). PT, donor-recipient sex mismatch, recipient diagnosis, recipient race, graft size, discontinuation of topical corticosteroids and immune-modulators, prior immunizations within 3 months, and prior glaucoma surgery were not associated with rejection (P > .01). Among clear grafts with an ECD measurement at baseline and 3 years (n = 913), endothelial cell loss (ECL) was greater in eyes that experienced a rejection episode (n = 27) than in those that did not (n = 886) (48% vs 38%, P = .03). Twelve of 44 eyes (27%) with definite graft rejection subsequently failed, comprising 15% of the 79 failures in the CPTS.

CONCLUSIONS

Graft rejection is uncommon after DSAEK and more likely with younger age, in a study cohort mostly > 50 years old. Rejection increases ECL, but it is not a leading cause of DSAEK failure.

Donor, Recipient, and Operative Factors Associated with Graft Success in the Cornea Preservation Time Study

PURPOSE

To associate donor, recipient, and operative factors with graft success 3 years after Descemet stripping automated endothelial keratoplasty (DSAEK) in the Cornea Preservation Time Study (CPTS).

DESIGN

Cohort study within a multicenter, double-masked, randomized clinical trial.

PARTICIPANTS

One thousand ninety individuals (1330 study eyes) with a median age of 70 years undergoing DSAEK for Fuchs endothelial corneal dystrophy (94% of eyes) or pseudophakic or aphakic corneal edema (PACE; 6% of eyes).

METHODS

Eyes undergoing DSAEK were randomized to receive a donor cornea with preservation time (PT) of 0 to 7 days (n = 675) or 8 to 14 days (n = 655). Donor, recipient, and operative parameters were recorded prospectively. Graft failure was defined as regraft for any reason, a graft that failed to clear by 8 weeks after surgery, or an initially clear graft that became and remained cloudy for 90 days. Failure in the first 8 weeks was classified further as primary donor failure or early failure, in the absence or presence of operative complications, respectively. Proportional hazards and logistic regression models were used to estimate risk ratios (RR) and 99% confidence intervals (CIs) for graft failure.

MAIN OUTCOME MEASURES

Graft success at 3 years.

RESULTS

One thousand two hundred fifty-one of 1330 grafts (94%) remained clear at 3 years and were considered successful. After adjusting for PT, tissue from donors with diabetes (RR, 2.35; 99% CI, 1.03-5.33) and operative complications (RR, 4.21; 99% CI, 1.42-12.47) were associated with increased risk for primary or early failure. Preoperative diagnosis of PACE (RR, 3.59; 99% CI, 1.05-12.24) was associated with increased risk for late failure by 3 years after surgery compared with Fuchs dystrophy. Graft success showed little variation among other factors evaluated, including donor age (RR, 1.19 per decade; 99% CI, 0.91-1.56 per decade), preoperative donor endothelial cell density (RR, 1.10 per 500 cells; 99% CI, 0.74-1.63 per 500 cells), graft diameter (RR, 1.22 per 1 mm; 99% CI, 0.39-3.76 per 1 mm), and injector use for graft insertion (RR, 0.92; 99% CI, 0.40-2.10).

CONCLUSIONS

Descemet stripping automated endothelial keratoplasty success in the early and entire postoperative period is more likely when the donor did not have diabetes and was without operative complications and in the long-term postoperative period in recipients with Fuchs dystrophy compared with those with PACE. Mechanisms whereby diabetic donors and PACE recipients reduce the rate of graft success after DSAEK warrant further study.

Incidence and Outcomes of Positive Donor Rim Cultures and Infections in the Cornea Preservation Time Study

PURPOSE

To assess donor rim culture results and outcomes of ocular infections in the Cornea Preservation Time Study (CPTS).

METHODS

Donor corneal rim cultures were optional. Donor characteristics were assessed for association with positive cultures using the Fisher exact test and Poisson regression analyses. Incidence rates of ocular infections were estimated, and 95% confidence intervals were calculated.

RESULTS

Cultures were performed in 784 (58.9%) of the 1330 cases. For the 0 to 7-day versus 8 to 14-day preservation time groups, respectively, positive fungal growth occurred in 10 of 397 (2.5%) versus 5 of 387 (1.3%) corneas (P = 0.30), whereas positive bacterial cultures occurred in 6 of 397 (1.5%) versus 4 of 387 (1.0%) corneas (P = 0.75). Surgeon-prepared tissue remained a significant risk for positive fungal cultures [relative risk (RR) of surgeon- versus eye-bank-prepared, 2.85; 95% CI (1.02-7.98)], whereas younger donors [RR per year of age, 0.96; 95% CI (0.93-1.00)] and accidental death donors [RR of accident versus disease, 3.71; 95% CI (1.36-10.13)] were at a greater risk for positive bacterial cultures. Fungal infection (Candida glabrata) developed in 1 (6.7%) of 15 recipients with a positive fungal culture, and no recipient infections occurred with positive bacterial culture. With one additional fungal keratitis (Candida albicans) and one bacterial endophthalmitis (E. coli) with no rim culture performed, a total of 2 of 1330 eyes (0.15%) developed fungal and 1/1330 eyes (0.08%) developed bacterial postkeratoplasty infections.

CONCLUSIONS

A longer preservation time was not associated with a higher rate of positive donor rim cultures. The overall rate of infection across the entire cohort was low.

Five-Year Graft Survival of Descemet Membrane Endothelial Keratoplasty (EK) versus Descemet Stripping EK and the Effect of Donor Sex Matching

PURPOSE

To determine whether the reduced risk of immunologic rejection with Descemet membrane endothelial keratoplasty (DMEK) results in a 5-year survival advantage relative to Descemet stripping endothelial keratoplasty (DSEK) and to determine whether matching the donor and recipient sex affects the rejection episode and graft survival rates.

DESIGN

Retrospective cohort study.

PARTICIPANTS

Patients with Fuchs' endothelial corneal dystrophy treated with DSEK or DMEK.

METHODS

This study reviewed 2017 consecutive cases (1312 DSEK and 705 DMEK) performed by 13 surgeons between 2003 and 2012 and included the surgeons' first cases. Survival rates were calculated by Kaplan-Meier analysis.

MAIN OUTCOME MEASURES

Immunologic rejection episodes, graft failure or replacement for any reason, and endothelial cell loss.

RESULTS

The 5-year rejection episode rate was lower with DMEK (2.6% vs. 7.9% with DSEK, relative risk, 0.29; 95% confidence interval, 0.16-0.53) despite early reduction of topical corticosteroids in 25% of the DMEK cases. African Americans (n = 46) had a higher risk of rejection episodes than other races (relative risk, 4.4; 95% confidence interval, 2.0-9.6). The cumulative 5-year survival rate was 93% with DSEK and DMEK (P = 0.86). Forty-four DMEK and 69 DSEK grafts failed or were replaced within 5 years, but only 1 DMEK and 4 DSEK failures followed a rejection episode. Rejection episodes increased endothelial cell loss (P = 0.004) but were not a significant risk factor for graft failure within 5 years (P = 0.90). The mean 5-year endothelial cell loss was similar between DMEK (48%±19%) and DSEK (47%±19%) (P = 0.22). Graft rejection episode and survival rates were not significantly influenced by whether the sex of the donor matched that of the recipient (rejection episodes: P = 0.07 for female recipients and P = 0.33 for male recipients; graft survival: P = 0.67 for female recipients and P = 0.17 for male recipients).

CONCLUSIONS

Five-year graft survival was similar between DMEK and DSEK. Although DMEK had a significantly lower risk of immunologic rejection, rejection episodes rarely resulted in graft failure within 5 years with either procedure. Sex matching the donor and recipient provided no survival advantage with DSEK or DMEK.