Factors Associated With Graft Rejection in the Cornea Preservation Time Study

Diabetes Endothelial Keratoplasty Study: Methods and Impact on the Use of Corneas From Donors With Diabetes for Descemet Membrane Endothelial Keratoplasty

PURPOSE

Describe aims, methods, characteristics of donors, donor corneas and recipients, and potential impact of the Diabetes Endothelial Keratoplasty Study (DEKS).

METHODS

The DEKS is a randomized, clinical trial to assess graft success and endothelial cell density (ECD) 1 year after Descemet membrane endothelial keratoplasty (DMEK) using corneas from donors with versus without diabetes in a 1:2 minimization assignment. Diabetes severity in the donor is assessed by medical history, postmortem HbA1c, and donor skin advanced glycation end-products and oxidation markers. A central image analysis reading center assesses baseline donor, 1-month and 1-year postoperative ECD.

RESULTS

The DEKS used corneas from 1154 donors for 1421 DMEK procedures on 1097 participants (324 bilateral) at 28 clinical sites. Forty-eight tissue preparations failed (3%). Mean donor age was 65 years; mean eye bank-determined screening ECD was 2709 cells/mm2. Ultimately, 106 (9%) of 1154 donors without diabetes history were classified as diabetic based on postmortem HbA1c ≥6.5%, and 509 (36%) of 1421 donor lenticules were classified as coming from diabetic donors. Recipients were 58% female, 96% White, and 53% phakic. Study eyes were treated for Fuchs endothelial corneal dystrophy (96%), pseudophakic corneal edema (2%), and failed endothelial keratoplasty (2%). Mean recipient age was 70 years; 21% had diabetes history and 26 (2%) had central laboratory determined HbA1c ≥6.5% without diabetes history.

CONCLUSIONS

The DEKS will increase understanding of factors related to DMEK success while determining whether diabetes and/or diabetes severity in the donor and/or recipient adversely affects graft success and endothelial cell loss.

Machine learning methods to identify risk factors for corneal graft rejection in keratoconus

Machine learning can be used to identify risk factors associated with graft rejection after corneal transplantation for keratoconus. The study included all keratoconus eyes that underwent primary corneal transplantation from 1994 to 2021. Data relating to the recipient, donor, surgery, and postoperative course that might be associated with the occurrence of a graft rejection reaction were compiled. This study used five supervised learning algorithms including artificial neural network, support vector machine, gradient boosting, extra trees classifier, and random survival forests to select the most predictive factors for graft rejection. A total of 1214 consecutive eyes of 985 keratoconus patients were included in the study, and the technique of keratoplasty included penetrating keratoplasty in 574 eyes (47.3%) and deep anterior lamellar keratoplasty in 640 eyes (52.7%). The overall prevalence of first graft rejection was 28.1%. All five models had similar ability in identifying predictive factors for corneal graft rejection. Technique of keratoplasty was associated with an increased risk of graft rejection in all models. Other identified risk factors included patient age, keratoplasty in the fellow eye, donor age, graft endothelial cell density, duration of corticosteroid application, time from keratoplasty to complete suture removal, and suture-associated complications. It is advisable that in the absence of any contraindication, post-transplant keratoconus eyes receive a low dose topical corticosteroid until all sutures are removed.

Clinical characteristics, risk factor analysis and outcomes in 61 eyes with graft rejection after descemet stripping endothelial keratoplasty, with a review of literature

PURPOSE

To report the demographic profile, clinical characteristics, risk factors and outcomes of graft rejection after DSEK.

METHODS

A total of 3073 eyes had DSEK between 2012 and 2019, of which 1710 eyes that had follow up of more than one year. Sixty-one eyes who had graft rejection during this period were studied.

RESULTS

Overall, incidence of graft rejection during the study period was 3.6% (61/1710 eyes) in those with follow up more than one year. The median age of patients was 58 (IQR 37.5-68) years. The indications were prior failed graft (34 eyes: 28 penetrating keratoplasty; 6 DSEK), post cataract surgery edema (12 eyes), Fuchs corneal endothelial dystrophy (6 eyes), corneal edema post inflammation (5 eyes) and iridocorneal endothelial syndrome (4 eyes). Of the 34 eyes with failed grafts, nine were post-rejection graft failures (two after endothelial keratoplasty and seven after penetrating keratoplasty), remaining 25 eyes were non-rejection graft failures. Ocular co-morbidities were noted in 41 eyes, of which secondary glaucoma was the most common (14 eyes). Clinical signs of graft rejection were diffuse edema, keratic precipitates and endothelial rejection line. Rejection episode occurred between 6-12 months after surgery in 20 (33%) eyes, 12-24 months in 15 (25%) eyes, 2-3 years in 12 (20%) eyes, and beyond 3 years in 14(23%) eyes. Graft clarity was restored in 55 (90%) eyes, which was complete in 41 (67%) eyes, partial in 14 (23%) eyes, and clarity was not restored in 6 (10%) eyes. The statistically significant risk factors for rejection were non-use of steroids (p value < 0.001), DSEK for failed graft (p value < 0.02) and DSEK for corneal edema post-inflammation (p value < 0.0014). DSEK for failed graft was a significant risk factor for graft failure after the rejection episode (p value < 0.05).

CONCLUSION

Graft rejection may occur as late as 5 years post-DSEK, emphasizing the need for long-term steroids instillation. Non-use of topical steroids, DSEK for failed graft and corneal edema post inflammation are risk factors for graft rejection. DSEK for failed graft was also seen as a risk factor for failure after the rejection episode The graft survival rate after the rejection episode was 90% at 6 months, 50% at 2 years and 10% at 5 years.

Corneal Transplant Rejection Postvaccination Among Medicare Beneficiaries

PURPOSE

The purpose of this study was to describe the incidence of corneal graft rejection after COVID and influenza vaccination.

METHODS

Patients 65 years or older undergoing penetrating keratoplasty or endothelial keratoplasty any time between 2016 and 2021 followed by COVID or influenza vaccination in 2021 among the 100% Medicare Fee-For-Service database were included. Demographic and ocular history characteristics of patients with (cases) and without graft rejection (controls) were compared using the χ 2 test.

RESULTS

After COVID (n = 31,398) and influenza (n = 24,290) vaccination, 0.45% (n = 140) and 0.17% (n = 41) patients developed rejection within 90 days, respectively. There was no difference in the rate of graft rejection within 90 days relative to 90 to 180 days after vaccination after both COVID (90 days: 0.45% vs. 180 days: 0.61%, P = 0.37) and influenza (90 days: 0.17% vs. 180 days: 0.29%, P = 0.11) vaccines. For COVID vaccination, patients who underwent penetrating keratoplasty (n = 51, 0.97%; vs. endothelial keratoplasty = 89; 0.34%, P < 0.001), history of rejection up to 1 year before vaccination (n = 13; 1.30% vs. no history = 127, 0.42%; P < 0.001), and having an ocular comorbidity (n = 110, 0.54% vs. no ocular comorbidity = 30, 0.27%; P = 0.001) had higher rates of graft rejections, and most rejections were after 1 year postkeratoplasty (87.14%, n = 122).

CONCLUSIONS

The incidence of graft rejection postvaccination is low compared with the overall rates of rejection in the published literature. Most post-COVID vaccination graft rejections were after 1 year postkeratoplasty when corticosteroids are expected to have been tapered to lower doses. Surgeons may counsel patients regarding graft rejection symptoms, but overall low rates may not warrant pretreatment in low-risk keratoplasty patients.

Descemet Endothelial Thickness Comparison Trial II (DETECT II): multicentre, outcome assessor-masked, placebo-controlled trial comparing Descemet membrane endothelial keratoplasty (DMEK) to Descemet stripping only (DSO) with adjunctive ripasudil for Fuchs dystrophy

INTRODUCTION

It remains uncertain whether Descemet membrane endothelial keratoplasty (DMEK) or Descemet stripping only (DSO) yields better outcomes in patients with symptomatic Fuchs endothelial corneal dystrophy (FECD). This paper presents the protocol for the Descemet Endothelial Thickness Comparison Trial II (DETECT II), a multicentre, outcome-masked, randomised, placebo-controlled, clinical trial comparing DMEK to DSO with ripasudil (DSO-R) for this patient population.

METHODS AND ANALYSIS

A total of 60 patients with endothelial dysfunction due to symptomatic FECD will be enrolled from seven participating sites in the USA. The patients will be randomly assigned in a 1:1 ratio to one of the following treatment groups: group 1-DMEK plus topical placebo and group 2-DSO plus topical ripasudil 0.4%. The enrolment period is 24 months. The primary outcome is best spectacle-corrected visual acuity at 12 months. Secondary outcomes include peripheral and central endothelial cell density, visual acuity, vision-related quality of life and Pentacam Scheimpflug tomography. Study outcomes will be analysed using mixed effects linear regression. Adverse events, including rebubble procedures, endothelial failure and graft rejection, will be documented and analysed using appropriate statistical methods. DETECT II aims to provide evidence on the comparative effectiveness of DMEK and DSO-R. The results of this trial will contribute to optimising the treatment of FECD, while also exploring the cost-effectiveness of these interventions. Dissemination of findings through peer-reviewed publications and national/international meetings will facilitate knowledge translation and guide clinical practice in the field of corneal transplantation.

ETHICS AND DISSEMINATION

A data and safety monitoring committee has been empanelled by the National Eye Institute. All study protocols will be subject to review and approval by WCG IRB as the single IRB of record. This study will comply with the National Institute of Health (NIH) Data Sharing Policy and Policy on the Dissemination of NIH-Funded Clinical Trial Information and the Clinical Trials Registration and Results Information Submission rule. Data from the trial will be made available on reasonable request.

TRIAL REGISTRATION NUMBER

NCT05275972.

Risk of Corneal Graft Rejection and Vaccination: A Matched Case-Control Study From a United States Integrated Health Care System

PURPOSE

Data on vaccine-associated corneal transplant rejections are limited. We examined the association between graft rejection and vaccination.

DESIGN

Matched case-control METHODS: We used electronic health records to identify corneal transplant recipients between January 2008 and August 2022 at Kaiser Permanente Southern California. Cases were transplant recipients who experienced a graft rejection (outcome) during the study period. Randomly selected controls who did not experience a corneal graft rejection at their matched cases' index date (rejection date) were matched in a 3:1 ratio to cases. For controls, index date was determined by adding the number of days between transplant and graft rejection of their matched case to the control's transplant date.

RESULTS

The study included 601 cases and 1803 matched controls (mean age 66 years [s.d. 17.0], 52% female, 47% non-Hispanic white). Twenty-three% of cases and 22% of controls received ≥1 vaccinations within 12 weeks prior to the index date. The adjusted odds ratio (aOR) for vaccination in the 12 weeks prior to index date, comparing cases to controls was 1.17 (95% CI: 0.91, 1.50]). The aOR was 1.09 (0.84, 1.43) for 1 vaccination, 1.53 (0.90, 2.61) for 2 vaccinations, and 1.79 (0.55, 5.57) for ≥3 vaccinations. The aOR was 1.60 (0.81, 3.14) for mRNA vaccines, and 1.19 (0.80, 1.78) for adjuvanted/high dose vaccines.

CONCLUSIONS

We found no evidence to suggest an association between vaccination and graft rejection. Our findings provide support for the completion of recommended vaccinations for corneal transplant recipients, without significantly increasing the risk of graft rejection.

Fuchs endothelial corneal dystrophy: an updated review

PURPOSE

The present review will summarize FECD-associated genes and pathophysiology, diagnosis, current  therapeutic approaches, and future treatment perspectives.

METHODS

Literature review.

RESULTS

Fuchs' endothelial corneal dystrophy (FECD) is the most common bilateral corneal dystrophy and accounts for one-third of all corneal transplants performed in the US. FECD is caused by a combination of genetic and non-heritable factors, and there are two types: early-onset FECD, which affects individuals from an early age and is usually more severe, and late-onset FECD, which is more common and typically manifests around the age of 40. The hallmark findings of FECD include progressive loss of corneal endothelial cells and the formation of focal excrescences (guttae) on the Descemet membrane. These pathophysiological changes result in progressive endothelial dysfunction, leading to a decrease in visual acuity and blindness in later stages. The present review will summarize FECD-associated genes and pathophysiology, diagnosis, current therapeutic approaches, and future treatment perspectives.

CONCLUSION

With the characterization and understanding of FECD-related genes and ongoing research into regenerative therapies for corneal endothelium, we can hope to see more significant improvements in the future in the management and care of the disease.

Management and prevention of corneal graft rejection

The management of an episode of corneal graft rejection (CGR) is primarily by corticosteroids. Immunomodulators are useful for long-term immunosuppression and in dealing with cases of high-risk (HR) corneal grafts. The classical signs of CGR following penetrating keratoplasty (PKP) include rejection line, anterior chamber (AC) reaction, and graft edema. However, these signs may be absent or subtle in cases of endothelial keratoplasty (EK). Prevention of an episode of graft rejection is of utmost importance as it can reduce the need for donor cornea significantly. In our previous article (IJO_2866_22), we had discussed about the immunopathogenesis of CGR. In this review article, we aim to discuss the various clinical aspects and management of CGR.

The impact of donor diabetes on corneal transplant immunity

Corneal transplantation is the most common form of solid tissue grafting, with an approximately 80% to 90% success rate. However, success rates may decline when donor tissues are derived from patients with a history of diabetes mellitus (DM). To evaluate the underlying immunopathologic processes that cause graft rejection, we used streptozotocin-induced type 1 DM (DM1) and transgenic Lepob/ob type 2 DM (DM2) diabetic murine models as donors and nondiabetic BALB/c as recipients. DM resulted in an increased frequency of corneal antigen-presenting cells (APCs) with an acquired immunostimulatory phenotype. Following transplantation, recipients that received either type of diabetic graft showed increased APC migration and T helper type 1 alloreactive cells, impaired functional regulatory T cells, and graft survival. Insulin treatment in streptozotocin-induced diabetic mice led to an increased tolerogenic profile of graft APC, lower T helper type 1 sensitization, and a higher frequency of functional regulatory T cells with high suppressive capacity, reflected in increased graft survival. We conclude that both DM1 and DM2 in donors can impact corneal APC functional phenotype, rendering the tissue more immunogenic and thereby increasing the risk of graft failure.

Trends and Surgeon Variations in Early Regrafts After Endothelial Keratoplasty: Analysis of the National Medicare Data Set

PURPOSE

The aims of this study were to determine national-level trends in early regraft rates and examine patient-level and surgeon-level characteristics associated with early regrafts.

METHODS

This was a retrospective, cohort study. We identified beneficiaries aged 65 years or older in the 2011 to 2020 Medicare carrier claims data set who underwent Endothelial keratoplasty (EK) and subsequently underwent an early regraft. The incidence of early regraft for each year was calculated and patient-level and surgeon-level characteristics associated with regrafts were examined using a multivariable regression model.

RESULTS

Of 114,383 EK procedures, 4119 (3.60%) were followed by an early regraft, with no significant variations in the rates between years ( P = 0.59). Factors associated with higher odds of early regraft were Black compared with White race (OR 1.151; 95% confidence interval (CI) 1.018-1.302) and the highest quartile of income versus the lowest quartile (OR 1.120; 95% CI 1.002-1.252). Factors associated with lower odds were female sex (OR 0.889; 95% CI 0.840-0.942), receiving surgery in a hospital-based outpatient department versus an ambulatory center (OR 0.813; 95% CI 0.740-0.894), and having a surgeon with the highest quartile of annual EK volume versus the lowest (OR 0.726; 95% CI 0.545-0.967). Early regraft rates among surgeons ranged from 0% to 58.8% with a median [interquartile range] of 3.13 [0-6.15].

CONCLUSIONS

We found no significant increases in the early regraft rates over the past decade in the United States. Patient male sex and Black race, ambulatory surgery center-based location of the surgery, and low surgeon EK volume were associated with early regrafts. Substantial surgeon variability in regraft rates may indicate opportunities for improvement through development of best practices on perioperative management and patient counseling.

A lack of an association between COVID-19 vaccination and corneal graft rejection: results of a large multi-country population based study

PURPOSE

The aim of the study was to present the rates of corneal transplant rejection from 2018 to 2022 at both Moorfields Eye Hospital UK, and Ospedali Privati Forli (OPF) "Villa Igea", Italy and evaluate the purported association between COVID-19 vaccination and rejection.

METHODS

We performed a retrospective review of rejection cases presenting to the two units. Monthly rates were correlated against regional vaccination programme rates. At OPF, conditional Poisson regression model was employed to estimate the incidence risk ratio (IRR) of graft rejection following COVID-19 vaccination risk period compared with the control period.

RESULTS

Between January 2018 and March 2022, there were 471 (Moorfields), 95 (OPF) episodes of rejection. From the start of vaccination programme in the UK in late January 2021, the median number of graft rejections per month at Moorfields was 6 (range: 5-9), which was not significantly different to post-lockdown, pre-vaccination programme (March 2020-January 2021), p = 0.367. At OPF, the median rates of rejection before and after initiation of the vaccination programme were not significantly different (p = 0.124). No significant increase in incidence rate of rejection in the risk period following COVID-19 vaccination was found (IRR = 0.53, p = 0.71).

CONCLUSION

No notable increase in rates of transplant rejection was noted in year 2021 when COVID-19 vaccination was broadly implemented. The apparent temporal relationship between COVID-19 vaccination and corneal graft rejection highlighted in several case reports may not represent a causative association.

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.

Machine Learning Analysis of Postkeratoplasty Endothelial Cell Images for the Prediction of Future Graft Rejection

Purpose

This study developed machine learning (ML) classifiers of postoperative corneal endothelial cell images to identify postkeratoplasty patients at risk for allograft rejection within 1 to 24 months of treatment.

Methods

Central corneal endothelium specular microscopic images were obtained from 44 patients after Descemet membrane endothelial keratoplasty (DMEK), half of whom had experienced graft rejection. After deep learning segmentation of images from all patients' last and second-to-last imaging, time points prior to rejection were analyzed (175 and 168, respectively), and 432 quantitative features were extracted assessing cellular spatial arrangements and cell intensity values. Random forest (RF) and logistic regression (LR) models were trained on novel-to-this-application features from single time points, delta-radiomics, and traditional morphometrics (endothelial cell density, coefficient of variation, hexagonality) via 10 iterations of threefold cross-validation. Final assessments were evaluated on a held-out test set.

Results

ML classifiers trained on novel-to-this-application features outperformed those trained on traditional morphometrics for predicting future graft rejection. RF and LR models predicted post-DMEK patients' allograft rejection in the held-out test set with >0.80 accuracy. RF models trained on novel features from second-to-last time points and delta-radiomics predicted post-DMEK patients' rejection with >0.70 accuracy. Cell-graph spatial arrangement, intensity, and shape features were most indicative of graft rejection.

Conclusions

ML classifiers successfully predicted future graft rejections 1 to 24 months prior to clinically apparent rejection. This technology could aid clinicians to identify patients at risk for graft rejection and guide treatment plans accordingly.

Translational Relevance

Our software applies ML techniques to clinical images and enhances patient care by detecting preclinical keratoplasty rejection.

Impact of gender mismatch on corneal graft rejection and rejection-related graft failure in repeat penetrating keratoplasty

PURPOSE

To explore the impact of gender mismatch on corneal allograft rejection and rejection-related graft failure in patients with repeat penetrating keratoplasty (PK).

METHODS

A retrospective cohort was conducted at Ramathibodi Hospital, Bangkok, Thailand. Patients with repeat PK and follow-up period of at least 6 months were recruited. Demographic data, pre-operative ocular findings and donor information were collected. Patients were divided into 2 groups according to gender mismatch between donor and recipient (male to female vs others). Survival analysis was performed using the Kaplan-Meier method. The association between risk factors and the outcomes of graft rejection and rejection-related graft failure were analyzed using Cox proportional hazards regression.

RESULTS

Of 68 patients with repeat PK, 26 patients (38.2%) were gender mismatched. There was no difference in 3-year rejection-free survival and graft survival between patients with gender mismatch and others (p = 0.698 and p = 0.402, respectively). Younger recipients (< 40 years) showed a significantly higher rejection rate compared to older recipients (hazard ratio; HR = 3.14, 95% confidence interval; CI 1.15 to 8.58), while patients with multiple PK (> 2 times) were found to be significantly associated with higher rejection-related graft failure compared to patients with 2 times or less PK (HR = 2.72, 95% CI 1.03 to 7.21). After multivariate analysis, only younger recipients demonstrated a statistical significance on graft rejection (adjusted HR = 2.86, 95% CI 1.04 to 7.84).

CONCLUSIONS

Gender mismatch might not impact corneal graft rejection or rejection-related graft failure in patients with repeat PK. Younger age was found to be a strong factor associated with graft rejection. Gender matching might not be compulsory for repeat PK.

COVID-19 Vaccination May Not Increase Rates of Corneal Graft Rejection

PURPOSE

The aim of the study was to present the rates of rejection from 2018 to 2021 and evaluate the purported association between COVID-19 vaccination and corneal graft rejection.

METHODS

Cases of corneal graft rejection diagnosed between January 2018 and December 2021 were reviewed. The conditional Poisson regression model of the self-controlled case series method was used to estimate the incidence risk ratio of graft rejection after COVID-19 vaccination risk period compared with the control period. Based on outcomes of eyes that underwent keratoplasty from January 2018 to December 2020, Cox proportional hazard models were fitted with previous COVID-19 vaccination as a time-varying covariate.

RESULTS

Over the past 4 years, the annual tally of diagnosed cases of graft rejection (19 cases in year 2018, 19 cases in year 2019, 21 cases in year 2020, and 18 cases in year 2021) has remained relatively stable. Using the conditional Poisson regression analysis, no significant increase in the incidence rate of rejection in the risk period after COVID-19 vaccination was found (incidence risk ratio = 0.56, 95% confidence interval [CI] = 0.13-2.28, P = 0.70). Fitted as a time-varying covariate, previous COVID-19 vaccination was not associated with graft rejection in both unadjusted (hazard ratio =0.77, 95% CI = 0.29-5.46, P = 0.77) and adjusted Cox models (hazard ratio = 0.75, 95% CI = 0.10-5.52, P = 0.78).

CONCLUSIONS

No notable increase in rates of corneal graft rejection was noted in year 2021 when COVID-19 vaccination was broadly implemented. The apparent temporal relationship between COVID vaccination and corneal graft rejection may not represent a causative association.

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.

Acute corneal allograft rejection following SARS-CoV-2 vaccination-A systematic review

All documented cases of acute corneal allograft rejection following SARS-CoV-2 vaccination were examined, to characterize possible risk factors and graft outcomes. Comprehensive search (4 electronic databases: PubMed, CENTRAL, ClinicalTrials.gov, Google Scholar, plus manual search in articles' reference lists) until March 1st 2022 to identify studies reporting acute corneal allograft rejection following SARS-CoV-2 vaccination; study protocol was developed in line with PRISMA statement. We analysed demographics, allograft type, rejection prophylaxis regime at the time of vaccination, transplantation-to-vaccination time (G-Vt), vaccination-to-immune reaction onset time (V-Rt), management, best-corrected visual acuity before and after rejection, and graft survival. Of 169 titles/abstracts screened, 16 studies (n  = 36 eyes) met the inclusion criteria. Fourteen eyes (38.9%) had received >1 graft, and 11.1% of cases had history of immune reactions; 52.9% of cases occurred after the first dose. Median (P25-P75) G-Vt was 48 (10-78) months; median V-Rt was 9 (7-14) days. In eyes with resolved rejection, median time-to-resolution was 3 (1-4) weeks. Four eyes (11.1%) had partial resolution of corneal decompensation, and 5 grafts (13.9%) failed. Acute corneal allograft rejection after SARS-CoV-2 vaccination is a rare event, but may occur any time post-keratoplasty. Early recognition and prompt, aggressive treatment is warranted to optimize vision and graft survival. Well-known risk factors for rejection may be confounding factors, including the high proportion of cases with a history of previous grafts and the rejection prophylaxis regimes at the time of vaccination. Increasing immunosuppressants in the peri-vaccination period may decrease the risk of immune reactions, especially in high-risk cases.

Impact of vaccination on keratoplasty

PURPOSE OF REVIEW

Corneal graft rejection has been reported after coronavirus disease 2019 (COVID-19) vaccination. The purpose of this review is to evaluate the literature regarding corneal graft rejection after vaccination, including rejection rates and risk factors. We aim to create a framework to identify patients who are at higher risk for graft rejection and may warrant consideration of prophylactic interventions.

RECENT FINDINGS

Graft rejection has been reported following administration of mRNA, viral vector, and inactivated whole-virion COVID-19 vaccines. Most cases had additional risk factors associated with rejection. Vaccination increases circulation of proinflammatory cytokines, CD4+ and CD8+ T-cell responses, and antispike neutralizing antibody, all of which may contribute to graft rejection. Two prospective studies have found no relationship between recent vaccination and rejection but 20% of cornea specialists report to have seen a vaccine-associated rejection and 22% recommend delaying vaccination in certain circumstances. Many specialists recommend prophylactic topical corticosteroids before and after vaccination to mitigate rejection risk but there is no evidence to support this practice on a wider scale.

SUMMARY

Our framework identified 96.8% of penetrating keratoplasty patients with vaccine-associated rejection as higher risk. Further research is needed in order to develop evidence-based guidelines.

Immunization-Associated Corneal Transplantation Rejection: A Review

PURPOSE

The purpose of this review was to examine and characterize the available literature regarding immunization-associated corneal graft rejection.

METHODS

A Literature search was conducted using PubMed keywords relevant to corneal transplantation, graft rejection, and immunization to find relevant publications through July 2021. Nine studies were included in this review. Data including patient demographics, type of transplant, chronology of disease, type of immunization, treatment, and outcomes were evaluated.

RESULTS

Twenty-three cases of corneal graft rejection associated temporally with immunizations have been described in the literature. Most of these patients were female, and most commonly had received the influenza vaccine before the rejection episode. Most episodes resulted in graft preservation with intensive corticosteroid therapy.

CONCLUSIONS

Immunization-associated corneal graft rejection is a rare but likely underreported phenomenon. Patients and surgeons should be aware of this possible risk, although the evidence is inconclusive. Conclusions are limited because of the small sample size and the retrospective nature of all existing literature on this subject. Surgeons should be encouraged to document and report these episodes.

Donor and Recipient Sex Matching and Corneal Graft Failure in High-Risk and Non-High-Risk Patients

Purpose

It is controversial whether donor-recipient sex mismatch is a risk factor associated with corneal graft failure. The purpose of this study was to investigate the effect of sex mismatch on corneal graft failure in high-risk and non-high-risk patients.

Design

A retrospective study.

Methods

The medical charts of patients who underwent corneal transplantations by one surgeon between 2012 and 2017 were reviewed. Patients were defined as high-risk for failure if they had glaucoma, ocular surface disease, or corneal vascularization. Graft failure rates were compared using the Kaplan–Meier survival curves between sex matched and mismatched subjects and between male-to-female grafting and other patients.

Results

One hundred and thirteen patients with a minimum follow-up of 18 months were included. In 62 non-high-risk patients, graft failure rates were similar between the sex mismatched and the sex matched recipients (p=0.645, log-rank) and in male donor to female recipient transplantations and in the other transplantations (p=0.496, log-rank). Analysis of fifty-one eyes of 51 high-risk graft recipients (mean age of 73.4 ± 12.7 years, N = 26 females) showed that graft failure rates were significantly higher in the sex mismatched than sex matched recipients (p=0.022, log-rank) and in male donor to female recipient transplantations than in the other transplantations (p=0.002, log-rank).

Conclusions

Sex matching for every patient bares logistic difficulties; however, in patients who are at high-risk for graft failure, it may be a simple way to improve outcomes and better utilize corneal grafts.

Gender Matching Did Not Affect 2-year Rejection or Failure Rates Following DSAEK for Fuchs Endothelial Corneal Dystrophy

PURPOSE

To investigate whether donor to recipient gender or H-Y mismatching was associated with graft rejection or failure following Descemet stripping automated endothelial keratoplasty (DSAEK) in patients with Fuchs endothelial corneal dystrophy (FECD).

DESIGN

Clinical cohort study.

METHODS

This study used a multi-center registry including patients aged >18 years who had undergone their first DSAEK for FECD between January 2008 and March 2018. The impact of donor and recipient gender incompatibility (including H-Y mismatches) on corneal graft rejection and failure was evaluated using Kaplan-Meier curves and univariable and multivariable Cox models.

RESULTS

Outcome data from 4341 eyes (3915 from the UK and 426 from Italy) were analyzed. Graft failure at 2-year follow-up occurred in 477 (11.0%) cases. Graft rejection at 2-year follow-up occurred in 175 cases (4.0%), 58 (1.3%) of whom developed graft failure. There was no significant effect of gender or H-Y mismatching on either rejection (P = .12, P = .06) or failure (P = .28, P = .14), respectively.

CONCLUSIONS

In patients with FECD undergoing DSAEK, no significant influence of gender and or H-Y mismatch on graft rejection or failure was found.

Refractory Recurrent Corneal Erosion after Descemet’s Stripping Automated Endothelial Keratoplasty

Purpose: To report a case of refractory recurrent corneal erosion that occurred after Descemet’s stripping automated endothelial keratoplasty (DSAEK) in iridocorneal endothelial syndrome.Case summary: A 62-year-old male patient with iridocorneal endothelial syndrome planned to undergo ultrathin DSAEK. At the surgery, corneal epithelial debridement was performed using a No. 15 blade to enhance the surgical field visibility. Three corneal venting incisions were made before graft insertion in the recipient eye. The corneal epithelium was healed at postoperative 1 week. However, the epithelium detached at 2 weeks postoperatively. The loosened epithelium was peeled off, and a therapeutic bandage contact lens was applied. Thereafter, the corneal epithelial detachment did not improve, despite repeated corneal epithelial debridement, prolonged therapeutic bandage contact lens wear, applications of 5% sodium chloride eyedrops and autoserum eyedrops, and intake of doxycycline, steroids, and valaciclovir. Anterior stromal puncture was performed three times, and the corneal epithelium eventually attached at postoperative 8 weeks. Although recurrent corneal erosion was not observed at postoperative 10 weeks, acute graft rejection occurred but improved with immunosuppressive treatment. The corrected visual acuity was 0.8 after cataract surgery, which was performed at 1 year after DSAEK.Conclusions: Refractory recurrent corneal erosion may occur after DSAEK surgery. In such a case, an aggressive treatment including the repeated anterior stromal puncture technique may be helpful.

Secondary Endothelial Keratoplasty-A Narrative Review of the Outcomes of Secondary Corneal Endothelial Allografts

BACKGROUND

We review the literature on the efficacy and safety outcomes of secondary Descemet stripping endothelial keratoplasty (DSEK) and Descemet membrane endothelial keratoplasty (DMEK).

METHODS

Literature search of English-written publications up to September 27, 2020 in PubMed database, using the terms "endothelial keratoplasty" in combination with keywords "secondary" or "repeat." In addition, we manually searched the references of the primary articles.

RESULTS

Twenty-seven studies (n = 651 eyes) were retained and reviewed, including 10 studies on repeat DSEK, 8 studies on repeat DMEK, 6 studies of DMEK following DSEK, and 3 studies of DSEK after failed DMEK. All studies reported significant improvement in visual acuity after secondary endothelial keratoplasty (EK). Twelve studies compared visual outcomes between primary and secondary EK, reporting conflicting findings. Sixteen studies reported endothelial cell loss rates after secondary EK, and only 1 study reported significantly increased endothelial cell loss rates compared with primary EK. Allograft rejection episodes occurred in 1.8% of eyes (range, 0%-50%). Six studies compared complication rates between primary and secondary EK eyes, and only 1 study found a higher median number of complications. However, 2 studies reported higher regraft failure rates compared with primary EK eyes.

CONCLUSIONS

Secondary EK is surgically feasible and renders significant visual improvement after failed primary EK, although it is not clear whether visual outcomes and allograft survival are comparable with primary EK, raising the question of whether secondary EK eyes are "low risk" as primary EK eyes. Further larger, prospective studies are encouraged to obtain additional quality data on secondary corneal endothelial allotransplantation.

Survey of Corneal Surgeons' Attitudes Regarding Keratoplasty Rejection Risk Associated With Vaccinations

PURPOSE

To investigate the attitudes and practice of corneal specialists if patients with keratoplasty sought advice regarding common vaccinations and risk for potential graft rejection.

METHODS

An online questionnaire was posted on the Kera-net listserv and the EuCornea Web site in early 2020. Attitudes toward vaccinations and keratoplasty were obtained. Decision making for common keratoplasty (endothelial keratoplasty, deep anterior lamellar keratoplasty, and penetrating keratoplasty) scenarios at early and late time points was explored regarding the herpes zoster and influenza vaccines.

RESULTS

There were 142 respondents: 51.1% (70/137) specifically advise their patients with keratoplasty to get all vaccinations; 19.7% (27/137) stated clinical experience of a vaccine-associated rejection episode; 42.2% (57/135) were unaware of any such cases; and 64% (27/42) of those concerned would recommend delay if within 3 months of transplant surgery, recent corneal infection, or a recent rejection episode. The 2245 total responses to 18 clinical scenarios demonstrated wide variability in management of grafts in the setting of vaccination. Generally, 45.9% would not alter management, 26.2% would increase frequency of topical steroids, and 22.2% would recommend delay to vaccinations. Increased concern was expressed with recent surgery, live zoster vaccine and higher-risk penetrating keratoplasty scenarios.

CONCLUSIONS

Nearly half of the respondents do not alter management in the setting of keratoplasty and zoster and/or influenza vaccinations. Anecdotal rejection episodes possibly associated with vaccinations were reported by some. Vaccine-related rejection has not been shown in higher-level research, but that has not eliminated clinical concerns. Prospective research into the true vaccine-related risks in keratoplasty is necessary if evidence-based management guidelines are to be developed or definitive reassurance provided.

Primary Graft Failure, Infection, and Endothelial Cell Density in Corneal Transplants With Increased Death-to-Preservation Time

PURPOSE

To ascertain whether death-to-preservation time (DPT) is associated with donor endothelial cell density (ECD), primary graft failure (PGF), and infection.

METHODS

Donor corneas aged older than 10 years with ECD 2000 to 4500 cells/mm2 were procured between 2011 and 2018 by a single eye bank. Donor corneas were analyzed retrospectively for the main outcome measures of PGF, infection, and ECD. Means and proportions of study parameters were compared between corneas with long and short DPT, defined as greater or less than 14 hours, respectively, excluding corneas with a history of intraocular surgery or diabetes. Multivariate analyses were performed using logistic regression, adjusting for donor age at time of death, history of diabetes mellitus, and history of cataract surgery.

RESULTS

Among 12,015 corneas, those with long DPT had a statistically but not clinically significant higher ECD than that of corneas with short DPT (2754 vs. 2724 cells/mm2, P < 0.01). There was no difference in PGF and infections in corneas with long versus short DPT (0.28% vs. 0.26%, P = 0.86; 0.43% vs. 0.29%, P = 0.51, respectively).

CONCLUSIONS

Longer DPT is not associated with a clinically meaningful reduction in donor ECD, PGF, or infection.

Transformation of electrospun Keratin/PVA nanofiber membranes into multilayered 3D Scaffolds: Physiochemical studies and corneal implant applications

In this study, we engineered an electrospun keratin/polyvinyl alcohol (PVA) nanofiber membrane with a three-dimensional (3D) fiber network. Both keratin and PVA are known as biocompatible materials, and the 3D assembly of these two led to a transparent membrane with superior mechanical properties. The as-prepared three-dimensionally assembled keratin/PVA nanofiber (3D keratin/PVA NFs) membrane was characterized by state-of-the-art techniques and used as a corneal implant in rabbit eyes. The transparency, mechanical properties, and biocompatibility of the electrospun keratin/PVA NFs were highly enhanced after 3D modification which is mainly attributed to its unique three-dimensional morphology. The performance of 3D keratin/PVA NFs membrane was compared with horse amniotic membrane (AM), and the results obtained from the clinical and histological evaluations showed that it could be considered as an alternative material to the AM. Furthermore, this study provides an emerging approach for converting a two-dimensional electrospun nanofiber membrane to three-dimensional fiber networks that resemble the structure of the extracellular matrix (ECM).

CorNeat KPro: Ocular Implantation Study in Rabbits

PURPOSE

The purpose of this study was to evaluate surgical feasibility and long-term integration of the CorNeat Keratoprosthesis (KPro), a novel synthetic cornea, in rabbits.

METHODS

The CorNeat KPro is a synthetic corneal implant designed to treat corneal blindness by using a polymeric scaffold for biointegration, consequently assimilating synthetic optics within ocular tissues. Eight New Zealand White rabbits were implanted unilaterally with the CorNeat KPro and observed for 6 months. Animals were regularly monitored by a certified ophthalmologist using slit-lamp biomicroscopy. One animal developed postoperative endophthalmitis and was removed from the study 7 weeks postsurgery. At termination, eyes were enucleated and evaluated histologically to assess local tissue integration and inflammatory response.

RESULTS

The surgical procedure was found feasible. The CorNeat KPro integrated into all operated eyes, resulting in a retention rate of 87.5% at the conclusion of the 6-month follow-up period. We observed minimal-to-mild conjunctival and iridial congestion and did not find additional inflammatory indicators, such as anterior chamber fibrin, flare, or cells. The optical element of the device remained clear with zero incidence of retroprosthetic membrane formation. Histopathological evaluation revealed comparable tissue and cellular reaction in all eyes, consisting of the presence of fibroblasts and associated collagen fibrils within the device's skirt component. Some eyes showed a mild foreign body reaction surrounding the skirt.

CONCLUSIONS

Clinical and histological findings indicate the integration of the implanted device into the surrounding tissue, evident by the retention rate and the diffuse infiltration of fibroblasts with collagen deposition among the device's fibrils. These data hold promise for clinical application in humans.

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.

Advances in corneal graft rejection

PURPOSE OF REVIEW

Immune rejection after corneal transplantation is a major risk for graft failure. We aim to summarize recent advances in the understanding and management of graft rejection.

RECENT FINDINGS

Immune rejection remains the leading cause of graft failure in penetrating keratoplasty (PKP). While ABO blood type and sex match between donor and recipient may reduce rejection, human leucocyte antigens class II matching in a randomized study did not reduce the risk of rejection in high-risk PKP. Compared with PKP, deep anterior lamellar keratoplasty, descemet stripping automated endothelial keratoplasty, and descemet membrane endothelial keratoplasty have lower immune rejection rates of 1.7-13%, 5-11.4%, and 1.7-2.8%, respectively, based on long-term (5 years and more) studies. Whether immune rejection is a major risk factor for graft failure in these lamellar keratoplasties is unclear. While there have not been major advances in the systemic management of graft rejection, topical nonsteroid agents such as tacrolimus and anti-vascular endothelial growth factor have shown promise in high-risk cases.

SUMMARY

Immune rejection remains the leading cause of graft failure in PKP. Lamellar keratoplasties have significantly lower rejection rates compared with PKP. The significance of rejection in the failure of lamellar grafts warrants further investigation.

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.

Evaluation of Donor and Recipient Characteristics Involved in Descemet Stripping Automated Endothelial Keratoplasty Outcomes

Aims: To evaluate both donor and recipient features involved in visual acuity restoring and complication insurgence in eyes that have undergone Descemet stripping automated endothelial keratoplasty (DSAEK).

Methods: In this retrospective study, charts of 111 eyes of 96 patients (mean age 70.25 ± 8.58 years) that underwent DSAEK were evaluated. Only Fuch's Distrophy (FD) or Bullous Keratopathy (BK) due to cataract surgery eyes were included. A complete ophthalmic check with endothelial cell density (ECD) and central corneal thickness (CCT) measurement was performed before surgery and at 1, 3, 6, and 12 months follow-up. Each DSAEK was performed by the same well-trained surgeon; only pre-cut lenticules, provided by same Eye Bank, were implanted.

Results: A total of 48 (43%) complications have been observed (most of them were 22 partial graft detachments and 17 IOP spikes). At the last follow-up (mean: 8.58 ± 4.09 months), a significant increase (p < 0.05) of best corrected visual acuity (BCVA) was detected. Overall mean BCVA of the eyes evaluated was 0.40 ± 0.43 LogMAR with BK eyes showing a significantly higher improvement (p < 0.05) compared to FD eyes. The only factor showing a significant correlation (p < 0.05) with visual acuity enhancement was the implant of a lenticule thinner than 100 μm. Recipient features significantly (p < 0.05) associated with complications observed after surgery were glaucoma and diabetes mellitus.

Conclusion: The use of a graft thinner than 100 μm can provide better visual acuity recovery while recipients affected by glaucoma or diabetes mellitus are more prone to develop complications after surgery.

Single-Pass Mikrokeratome and Anterior Chamber Pressurizer for the Ultrathin Descemet-Stripping Automated Endothelial Keratoplasty Graft Preparation

PURPOSE

To compare the reliability of microkeratome dissection with the anterior chamber pressurizer (ACP) system versus conventional pressurization for ultrathin Descemet-stripping automated endothelial keratoplasty (UT-DSAEK) graft preparation.

METHODS

A retrospective review of a consecutive series of dissected donor corneas processed at Pavia Eye Bank for UT-DSAEK surgery was performed. Grafts were prepared through single-pass microkeratome dissection with artificial anterior chamber internal pressure regulation through either ACP or the conventional method using a water column with tube clamp. The target central graft thickness (CGT) was ≤100 μm. Cutting predictability was determined as the difference between the microkeratome head size and the thickness actually removed. Graft regularity was investigated as central-to-peripheral thickness increase, central-to-peripheral (CP) ratio, and graft thickness uniformity. Thickness was measured with anterior segment optical coherence tomography (horizontal and vertical meridians).

RESULTS

Of the 265 UT-DSAEK grafts, ACP achieved the target "CGT ≤ 100 μm" in 87 of 120 (72.5%), whereas the conventional technique achieved the same in 85 of 145 (58.6%) (P = 0.018). ACP predictability was -3.9 μm (SD: 2.3), whereas predictability of the conventional technique was -54.6 μm (SD: 3.7) (P < 0.001). Thickness increased similarly (P = 0.212); CP ratio was better with ACP for only 2 mm diameter (P = 0.001); graft thickness uniformity was comparable (P > 0.05).

CONCLUSIONS

Compared with conventional pressurization, ACP improved microkeratome-assisted preparation reliability of UT-DSAEK grafts, achieving CGT ≤ 100 μm with significantly higher frequency (P = 0.018) and predictability (P < 0.001). ACP improved CP ratio only at 2 mm (P = 0.001); for other graft thickness, the 2 methods proved equivalent.

Risk Factors for Repeat Keratoplasty after Endothelial Keratoplasty in the Medicare Population

PURPOSE

To evaluate long-term rates of repeated keratoplasty after endothelial keratoplasty (EK), and to explore risk factors associated with graft failure.

DESIGN

Retrospective, cohort study.

METHODS

Population-based using 2010-2019 Medicare carrier claims.

STUDY POPULATION

Medicare beneficiaries aged ≥65 years who underwent endothelial keratoplasty (EK) procedures. Main outcome measures were 1) occurrence of repeated keratoplasty for the overall cohort as well as stratified by clinical indication, and 2), risk factors associated with repeated keratoplasty. The probability of undergoing repeated keratoplasty for different indications was estimated using the Kaplan-Meier method and compared using the log-rank test. A Cox proportional hazards regression model was constructed to determine patient and physician factors associated with the risk of repeated keratoplasty.

RESULTS

A total of 94,829 Medicare EK procedures (N = 71,040 unique patients) were included in the analysis. Over the study period, 11,013 of 94,829 EK procedures were followed by repeated keratoplasty. The overall probability of receiving a repeated keratoplasty was 6.1% at 6 months, 7.6% at 1 year, 14.3% at 5 years and 16.9% at 8 years. The probability of repeated keratoplasty was highest for procedures performed for prior failed grafts: 10.2% at 1 year, 29.9% at 8 years. Whereas 6.4% and 11.4% of grafts performed for Fuchs' endothelial dystrophy (FED) required repeated keratoplasty at 1 and 8 years of follow-up, respectively. For bullous keratoplasty and/or corneal edema, 8.6% and 22% of grafts underwent repeated keratoplasty at 1 and 8 years, respectively. In a multivariate analysis, patient factors associated with increased risk of repeated keratoplasty were black (hazard ratio [HR]: 1.29; 95% confidence interval [CI]: 1.20-1.38) or Asians (HR: 1.26; 95% CI: 1.10-1.45) having a glaucoma diagnosis (HR: 1.53; 95% CI: 1.46-1.60), prior glaucoma surgery (HR: 1.26; 95% CI: 1.18-1.35), and concurrent glaucoma surgery (HR: 1.31; 95% CI: 1.20-1.44). Surgeons with higher EK volumes had a decreased risk of repeated keratoplasty. Physicians who graduated medical school >30 years previously had increased risk of repeated keratoplasty compared to those who graduated within 10 years (HR: 1.16; 95% CI: 1.10-1.23).

CONCLUSIONS

Blacks or Asians, comorbid glaucoma, concurrent or prior glaucoma surgery, and lower volumes of surgery are associated with increased risk of repeated keratoplasty. Racial disparities identified in this study warrant further investigation.

Postoperative Complications in Medicare Beneficiaries Following Endothelial Keratoplasty Surgery

PURPOSE

To determine national-level incidence rates of major postoperative complications following endothelial keratoplasty (EK) procedures and to stratify these rates based on EK indications over an 8-year period using Medicare claims data.

DESIGN

Retrospective, cohort study.

METHODS

Setting: population-based; study population: Medicare beneficiaries aged ≥65 years who underwent EK procedures; main outcome measurements: 1) occurrence of major postoperative complications (i.e., endophthalmitis, choroidal hemorrhage, infectious keratitis, cystoid macular edema [CME], retinal detachment [RD], or RD surgery) following EK surgery; 2) time-to-event analysis for glaucoma surgery; and 3) occurrence of graft complications.

RESULTS

A total of 94,829 EK procedures (n = 71,040 unique patients) were included in the analysis. Of the total, 29% of patients had pre-existing glaucoma. The overall 90-day cumulative incidence of postoperative endophthalmitis and choroidal hemorrhage following EK was 0.03% and 0.05%, respectively. The overall 1-year cumulative rates of RD or RD surgery, infectious keratitis, and CME were 1.0%, 0.8%, and 4.1%, respectively. Approximately 7.6%, 12.2%, and 13.8% of all eyes in this study needed glaucoma surgery at 1-, 5-, and 8-years of follow-up, respectively. The probability of glaucoma surgery among patients with pre-existing glaucoma was 29% vs. 8% among those without pre-existing glaucoma at 8 years. The cumulative probabilities of developing any graft complications were 13%, 23.2%, and 27.1% at 1, 5, and 8 years, respectively, of follow-up. On average, patients undergoing EK procedures for a prior failed graft had the highest rate of complications, whereas those with Fuchs' corneal endothelial dystrophy had the lowest.

CONCLUSIONS

The incidence of major postoperative complications including endophthalmitis, retinal detachment, and choroidal hemorrhage following EK procedures is low. A high proportion of eyes undergoing EK eventually require glaucoma surgery and experience graft-related complications. Postoperative outcomes are typically worse for patients undergoing EK for prior failed grafts than for those undergoing EK for Fuchs' corneal endothelial dystrophy.

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.

An endothelial rejection line following Descemet stripping automated endothelial keratoplasty

Background

The endothelial rejection line is rarely seen after Descemet stripping automated endothelial keratoplasties (DSAEKs). Here, we present a case of endothelial graft rejection with an endothelial rejection line occurring 1 year after the procedure.

Case presentation

A 58-year-old female presented with graft rejection 1 year following a DSAEK procedure. The episode started when she tapered down her loteprednol to once a day. Slit-lamp examination showed a mildly injected conjunctiva with 1+ corneal oedema. On the posterior surface of the cornea, there was an endothelial rejection line (Khodadoust line) with keratic precipitates and multiple areas of anterior synechia.

Conclusion

The classic endothelial rejection line should be kept in mind as a rare sign of DSAEK graft rejection.

Risk factors for endothelial cell loss after Descemet membrane endothelial keratoplasty (DMEK)

This study aimed to identify the risk factors for endothelial cell density (ECD) loss after Descemet membrane endothelial keratoplasty (DMEK) and analyse whether donor tissues from cold versus organ culture differ in terms of ECD loss after DMEK. Consecutive DMEK cases from a prospective database for Fuchs’ endothelial corneal dystrophy were retrospectively analysed between 2011 and 2016 at the University of Cologne, and the possible risk factors for ECD loss, including patient-related factors, type of tamponade (air or 20% sulphur hexafluoride gas), type of surgery (triple DMEK or DMEK alone), re-bubbling, immune rejection, and donor-related factors were determined. Eight hundred and forty-one eyes were selected. There was no significant difference in the best-corrected visual acuity (logarithm of the minimal angle of resolution) and corneal thickness (P = 0.540 and P = 0.667) between groups. Immune reactions were more common in cold cultures (P = 0.019), but ECD loss (1 year after DMEK) was greater in organ cultures (38.3 ± 0.8%) than in cold cultures (34.7 ± 1.4%) (P = 0.022). Only re-bubbling was significantly associated with ECD loss (P < 0.001). Re-bubbling was found to be a key factor for ECD loss at 1 year after DMEK.

Quantitative and qualitative evaluation of deep learning automatic segmentations of corneal endothelial cell images of reduced image quality obtained following cornea transplant

We are developing automated analysis of corneal-endothelial-cell-layer, specular microscopic images so as to determine quantitative biomarkers indicative of corneal health following corneal transplantation. Especially on these images of varying quality, commercial automated image analysis systems can give inaccurate results, and manual methods are very labor intensive. We have developed a method to automatically segment endothelial cells with a process that included image flattening, U-Net deep learning, and postprocessing to create individual cell segmentations. We used 130 corneal endothelial cell images following one type of corneal transplantation (Descemet stripping automated endothelial keratoplasty) with expert-reader annotated cell borders. We obtained very good pixelwise segmentation performance (e.g., Dice coefficient = 0.87 ± 0.17 , Jaccard index = 0.80 ± 0.18 , across 10 folds). The automated method segmented cells left unmarked by analysts and sometimes segmented cells differently than analysts (e.g., one cell was split or two cells were merged). A clinically informative visual analysis of the held-out test set showed that 92% of cells within manually labeled regions were acceptably segmented and that, as compared to manual segmentation, automation added 21% more correctly segmented cells. We speculate that automation could reduce 15 to 30 min of manual segmentation to 3 to 5 min of manual review and editing.

Autologous Descemet Stripping Automated Endothelial Keratoplasty to Eliminate Endothelial Rejection in Eyes at High Risk

PURPOSE

To determine whether autologous Descemet stripping endothelial keratoplasty is technically feasible and whether it eliminates the risk of endothelial rejection in "only eyes" at high risk of immunological rejection.

METHODS

This is a prospective observational interventional study from 2016 to 2018 with a 24-month follow-up in a tertiary-level corneal referral center, Forlì, Italy. One 25-year-old woman with failed penetrating keratoplasty after endothelial rejection in the context of chronic panuveitis and a blind fellow eye due to retinal detachment underwent autologous Descemet stripping automated keratoplasty. An endothelial graft was harvested from the fellow eye by performing a hinged, microkeratome-assisted superficial stromal flap, with removal of the central posterior stromal bed. The posterior lamellar graft created was then transplanted into the other eye using a standardized Descemet stripping automated endothelial keratoplasty (DSAEK) technique. Main outcome measures were endothelial rejection, best spectacle-corrected visual acuity, and endothelial cell density.

RESULTS

No endothelial rejection was seen during the 2-year follow-up duration. Stable improvement in best spectacle-corrected visual acuity from 0.2 to 0.4 (decimal Snellen) was observed. Endothelial cell density of 1465 (cells/mm) was recorded at the final follow-up.

CONCLUSIONS

The use of this repeatable technique to harvest and transplant an autologous DSAEK graft eliminates endothelial rejection in high-risk eyes.

Experimental models of corneal endothelial cell therapy and translational challenges to clinical practice

The human corneal endothelium (CE) is a post-mitotic monolayer of endothelial cells, thought to be incapable of in vivo regeneration. Dysfunction of the CE is a commonly cited indication for corneal transplantation, with corneal blindness being the fifth most common cause of blindness globally. In 2012 alone 184,576 corneal transplants were performed in 116 countries (Gain et al., 2016). Presently, outcomes following human corneal transplantation have been reported to have over 97% success rate in restoring the recipient's vision (Patel et al., 2019). However, the continuing demand for cadaveric human corneas has driven research into alternative sources of CE and with the advent of protocols to produce cultured hCECs there is now the potential for cell therapy to regenerate the damaged CE. This review aims to examine the merits and limitations of different types of human and animal models used so far to test the concept of CE cell therapy.

Machine learning for segmenting cells in corneal endothelium images

Images of the endothelial cell layer of the cornea can be used to evaluate corneal health. Quantitative biomarkers extracted from these images such as cell density, coefficient of variation of cell area, and cell hexagonality are commonly used to evaluate the status of the endothelium. Currently, fully-automated endothelial image analysis systems in use often give inaccurate results, while semi-automated methods, requiring trained image analysis readers to identify cells manually, are both challenging and time-consuming. We are investigating two deep learning methods to automatically segment cells in such images. We compare the performance of two deep neural networks, namely U-Net and SegNet. To train and test the classifiers, a dataset of 130 images was collected, with expert reader annotated cell borders in each image. We applied standard training and testing techniques to evaluate pixel-wise segmentation performance, and report corresponding metrics such as the Dice and Jaccard coefficients. Visual evaluation of results showed that most pixel-wise errors in the U-Net were rather non-consequential. Results from the U-Net approach are being applied to create endothelial cell segmentations and quantify important morphological measurements for evaluating cornea health.