Endothelial cell changes as an indicator for upcoming allograft rejection following descemet membrane endothelial keratoplasty

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.

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.

Risk Factors for Descemet Membrane Endothelial Keratoplasty Rejection: Current Perspectives- Systematic Review

Descemet membrane endothelial keratoplasty (DMEK) is a corneal endothelial transplantation procedure with selective removal of a patient's defective Descemet membrane and endothelium. It is replaced with a healthy donor Descemet membrane and endothelium without a stromal component. Corneal graft rejection can be at the level of epithelium, stroma as well endothelium. DMEK graft rejection is relatively less common than rejection with DSAEK or penetrating keratoplasty, and a good outcome may be achieved with prompt management. The clinical picture of DMEK rejection is usually similar to endothelial rejection in Descemet Stripping Endothelial Keratoplasty (DSEK/DSAEK), which generally manifests as pain, redness, reduction in visual acuity, stromal edema, endothelial rejection line, keratic precipitates at the back of the cornea and corneal neovascularization. However, more subtle forms of rejection or immune reactions are more common in DMEK compared to DSAEK eyes. Early clinical diagnosis, prompt intervention, and meticulous management safeguard visual acuity and graft survival in these cases. Intensive topical steroids form the mainstay in the management of DMEK rejection. Sometimes, oral or intravenous steroids or other systemic immunomodulators may be required. DMEK graft failure can be primary or secondary, and failure usually requires a second procedure in the form of repeat DMEK or DSEK or penetrating keratoplasty (PKP). A detailed literature search was performed using search engines such as Google Scholar, PubMed, and Google books, and a comprehensive review on DMEK rejection was found to be lacking. This review is a comprehensive update on the risk factors, pathophysiology, primary and secondary graft failure, recent advances in diagnosis, prevention of rejection, and updates in the management of DMEK rejection. The review also discusses the differential diagnosis of DMEK failure and rejection, prognosis, and future perspectives considering DMEK failure and rejection.

Descemet membrane endothelial keratoplasty: Update on preoperative considerations, surgical techniques, and outcomes

Descemet membrane endothelial keratoplasty (DMEK) is the closest to the physiological replacement of endothelial cells. In the initial years, the technique was surgically challenging. Over the years, with better understanding and modifications in the surgical steps, the technique has evolved as an alternative to more popular procedure Descemet stripping endothelial keratoplasty. The article highlights the various preoperative, intraoperative, and postoperative nuances of DMEK. Additionally, it summarizes the various comparative and noncomparative studies on DMEK outcomes.

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.

Prevalence and severity of cornea guttata in the graft following Descemet Membrane Endothelial Keratoplasty (DMEK)

PURPOSE

The aim of this study was to determine the prevalence and severity of cornea guttata (CG) in grafts after Descemet membrane endothelial keratoplasty (DMEK) and to investigate its impact on various clinical parameters during follow-up.

METHODS

This retrospective study included 664 operations (DMEK and triple-DMEK) on 466 patients. The prevalence and progression of CG after the operation were examined using endothelial specular microscopy images. The severity grade of CG was classified into four grades: G0 without CG, G1 - G3 with increasing severity of CG. Clinical parameters such as central corneal thickness (CCT), visual acuity (VA), endothelial cell density (ECD), pleomorphism and polymegalism were examined during a postoperative follow-up time of 19.6 ± 15.8 months.

RESULTS

Cornea guttata (CG) appeared postoperatively in 124 (18.7%) eyes. 112 (16.9%) could be classified as G1, 9 (1.4%) as G2 and only 3 (0.5%) as G3. The examination of clinical parameters showed significant differences between healthy and low-grade CG (G0/G1) and high-grade CG (G2/G3). A significant deterioration was found in the corrected distance visual acuity (CDVA) (p = 0.02). CCT showed an increase between G0 (534 ± 58 μm) and G2 (549 ± 71 μm)/G3 (558 ± 56 μm) with a p-value of 0.02. Additionally, a significant increase in pleomorphism (p = 0.003) and polymegalism (p = 0.04) was detected.

CONCLUSION

Cornea guttata (CG) prevalence after DMEK and triple-DMEK was found to be 18.7%, although most of these cases were classified as low-grade CG and showed no clinical significance. Around 1.9% were classified as high-grade CG and significantly affected several clinical parameters during the follow-up.

Preventive treatment of allograft rejection after endothelial keratoplasty: A systematic review and meta-analysis

PURPOSE

To evaluate the efficacy of preventive treatment against allograft rejection after endothelial keratoplasty (EK), we conducted a systematic review and meta-analysis.

METHOD

PubMed, Cochrane Library, Embase and ScienceDirect databases were searched until May 2021. We computed a random-effect meta-analysis on graft rejection rate stratified by the intervention (i.e. Descemet membrane EK (DMEK) and Descemet stripping (Automated) EK (DS(A)EK) or ultrathin (UT)-DSAEK), and postoperative treatment. Meta-regressions were performed to compare intervention, treatment and influence of putative confusion factors.

RESULTS

We included 49 studies and 12 893 EK (6867 DMEK and 6026 DS(A)EK/UT-DSAEK). Topical steroids were merged in two efficacy regimens: standard steroids (prednisolone acetate 1% or dexamethasone 0.1%) and soft steroids (fluorometholone 0.1% or loteprednol etabonate 0.5%). Globally, DMEK had a lower graft rejection rate than DS(A)EK/UT-DSAEK (coefficient - 3.3, 95 CI, -4.60 to -1.90; p < 0.001). No significant differences were observed between standard and soft steroids to prevent graft rejection after DMEK. After EK, the rate of ocular hypertension was 20% (95 CI, 14 to 26%) with the use of standard steroids and 7% (5 to 9%) with soft steroids. Comparisons of treatments were not feasible in DS(A)EK/UT-DSAEK due to a lack of studies.

CONCLUSIONS

Descemet membrane endothelial keratoplasty (DMEK) has less risk of graft rejection compared with DS(A)EK/UT-DSAEK. Furthermore, soft steroids seemed to be a valuable alternative to standard steroids to prevent graft rejection after DMEK, involving a safe profile against ocular hypertension. Further studies are needed to compare other drugs in the prevention of graft rejection after EK.

Effects of uncomplicated Descemet membrane endothelial keratoplasty on the central retinal thickness

Purpose

To determine retinal thickness (RT) changes and the incidence of macular edema after uncomplicated Descemet membrane endothelial keratoplasty (DMEK-ME) in patients without ME risk factors.

Methods

In this retrospective study, 107 pseudophakic eyes of 74 patients with Fuchs endothelial dystrophy (FED) (79.4%) or bullous keratopathy (BK) (20.6%) underwent DMEK surgery between 2016 and 2019 at the Department of Ophthalmology, RWTH Aachen University. Patients with intra- or postoperative complications as well as pre-existing risk factors for ME were excluded. Macular spectral-domain optical coherence tomography (SD-OCT) and best spectacle-corrected visual acuity (BSCVA) measurements were performed before, 1 week, 1 month, and 6 months after surgery. Retinal thickness (RT) was analyzed in the central foveal 1 mm (CSF), parafoveal 3 mm and 6 mm subfield.

Results

Eight eyes (7.5%) developed DMEK-ME 1 month after surgery. Six DMEK-ME eyes (75%) were rebubbled, compared with 31.3% (31 of 99; P = 0.02) of the non DMEK-ME eyes. DMEK-ME eyes had a significantly thicker CSF 1 month after surgery (432.0 ± 97.6 μm) compared with non-DMEK-ME eyes (283.7 ± 22.2 μm; P = 0.01). The other subfields and time points showed no significant RT changes. DMEK-ME significantly impaired BSCVA (0.38 ± 0.92 logMAR) only 1 month after surgery in comparison to the non DMEK-ME eyes (0.23 ± 0.87 logMAR, P = 0.015).

Conclusion

Excluding systemic and surgery-related risk factors, rebubbling increases the risk of DMEK-ME. Performing a CSF scan 1 month after surgery, particularly in rebubbled eyes, efficiently detects DMEK-ME and allows the prompt initiation of treatment, e.g., topical corticosteroid and non-steroidal (NSAID) eye drops.

Corneal graft failure: an update

Corneal graft surgery is one of the most successful forms of human solid-tissue transplantation, and nowadays, there is a worldwide expansion of the surgical volume of corneal grafts. This surgery is continuously evolving, with new surgical techniques and postoperative treatments that have considerably increased the chance of survival for the grafts. Despite the high rate of success, corneal transplantation is still complicated by a relevant risk of graft failure. This study investigates the causes that lead to the failure of the different corneal graft surgical techniques and provides an updated synthesis on this topic. A comprehensive review of the main pathological pathways that determine the failure of corneal grafts is provided, analysing the main risk factors and disclosing the survival rates of the principal form of corneal grafts. Our results revealed that penetrating keratoplasty has higher failure rates than lamellar keratoplasty, with immunological rejection being the leading cause of graft failure, followed by late endothelial failure (LEF) and ocular surface disorders. Postoperative glaucoma and dehiscence of the surgical wound represent other important causes of failure. Endothelial keratoplasty showed the lowest rates of failure in the mid-term, with LEF, detachment of the graft and primary graft failure representing the most common pathological reasons for failure.

Combined specular microscopy and Scheimpflug imaging to improve detection of an upcoming allograft rejection after DMEK

PURPOSE

To assess whether combined analysis of specular microscopy and Scheimpflug imaging improves detection of an upcoming allograft rejection following Descemet membrane endothelial keratoplasty (DMEK).

METHODS

Retrospective analysis of 22 eyes that had developed a clinical proven allograft rejection 28 (±22) months (range: 4-84 months) after DMEK. Specular microscopy and Scheimpflug images routinely made after DMEK were retrospectively analysed for changes in endothelial cell morphology (e.g. nuclear activation), cell density (>10%) and pachymetry (>7%), and/or the presence of subclinical keratic precipitates. The same parameters were evaluated for 22 control eyes matched for age, gender and surgery indication.

RESULTS

A total of 20/22 eyes (91%) showed detectable changes 0.25-75 months before allograft rejection became clinically manifest: 13/22 (59%) showed both specular microscopy and Scheimpflug imaging changes; 5/22 (23%) only had changes on Scheimpflug imaging; and 2/22 (9%) only had specular microscopy changes. In 18/22 (82%) and 14/22 (64%) eyes, subclinical keratic precipitates and endothelial cell morphology changes could be detected, respectively. A total of 11/22 (50%) eyes concurrently showed a >10% drop in endothelial cell density and 4/22 (18%) a >7% pachymetry increase. Of the control eyes, 7/22 (32%) showed changes with specular microscopy but not with Scheimpflug imaging.

CONCLUSIONS

Combined analysis of specular microscopy and Scheimpflug imaging may allow recognizing an upcoming allograft rejection in over 90% of eyes and up to 6 years before rejection becomes clinically manifest. Early recognition of eyes at risk may allow for targeted intensified steroid treatment to prevent endothelial cell damage associated with rejection.

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.

Descemet Membrane Endothelial Keratoplasty Versus Descemet Stripping Automated Endothelial Keratoplasty and Penetrating Keratoplasty

PURPOSE

To compare the long-term graft survival outcomes and complications of patients who underwent Descemet membrane endothelial keratoplasty (DMEK), Descemet stripping automated endothelial keratoplasty (DSAEK), and penetrating keratoplasty (PK) for Fuchs endothelial corneal dystrophy (FECD) and bullous keratopathy (BK).

DESIGN

Retrospective comparative cohort study.

METHODS

Patients with FECD and BK who underwent DMEK (121 eyes), DSAEK (423 eyes), or PK (405 eyes) from the prospective cohort from the Singapore Corneal Transplant Registry were included. A Kaplan-Meier survival analysis was conducted to compare the survival probabilities of the 3 groups. The main outcome measure was graft survival.

RESULTS

The DMEK group had the best overall cumulative graft survival of 97.4%, compared to DSAEK (78.4%) and PK (54.6%) (P < .001). In eyes with FECD, the DMEK group had the best graft survival of 98.7% compared to DSAEK (96.2%) and PK (73.5%) (P = .009). The graft survival in eyes with BK was poorer overall; however, the DMEK group still had the best graft survival of 94.7%, compared to DSAEK (65.1%) and PK (47.0%, P = .001). Eyes that underwent DMEK had the lowest rate of graft rejection (1.7% vs DSAEK 5.0% vs PK 14.1%, P < .001) and postoperative elevation of intraocular pressure (11.6% vs DSAEK 23.6% vs PK 22.5%, P = .015).

CONCLUSIONS

Patients who underwent DMEK for FECD and BK had better graft survival compared to DSAEK and PK. Eyes that underwent DMEK also had a significantly lower rate of graft rejection and elevated intraocular pressure compared to DSAEK and PK for the same indications.

Immune reactions after modern lamellar (DALK, DSAEK, DMEK) versus conventional penetrating corneal transplantation

In the past decade, novel lamellar keratoplasty techniques such as Deep Anterior Lamellar Keratoplasty (DALK) for anterior keratoplasty and Descemet stripping automated endothelial keratoplasty (DSAEK)/Descemet membrane endothelial keratoplasty (DMEK) for posterior keratoplasty have been developed. DALK eliminates the possibility of endothelial allograft rejection, which is the main reason for graft failure after penetrating keratoplasty (PK). Compared to PK, the risk of endothelial graft rejection is significantly reduced after DSAEK/DMEK. Thus, with modern lamellar techniques, the clinical problem of endothelial graft rejection seems to be nearly solved in the low-risk situation. However, even with lamellar grafts there are epithelial, subepithelial and stromal immune reactions in DALK and endothelial immune reactions in DSAEK/DMEK, and not all keratoplasties can be performed in a lamellar fashion. Therefore, endothelial graft rejection in PK is still highly relevant, especially in the "high-risk" setting, where the cornea's (lymph)angiogenic and immune privilege is lost due to severe inflammation and pathological neovascularization. For these eyes, currently available treatment options are still unsatisfactory. In this review, we will describe currently used keratoplasty techniques, namely PK, DALK, DSAEK, and DMEK. We will summarize their indications, provide surgical descriptions, and comment on their complications and outcomes. Furthermore, we will give an overview on corneal transplant immunology. A specific focus will be placed on endothelial graft rejection and we will report on its incidence, clinical presentation, and current/future treatment and prevention options. Finally, we will speculate how the field of keratoplasty and prevention of corneal allograft rejection will develop in the future.

In Vivo Confocal Microscopy Demonstrates Increased Immune Cell Densities in Corneal Graft Rejection Correlating With Signs and Symptoms

PURPOSE

Diagnosis of graft rejection is based on patient symptoms and on clinical signs detected by slit-lamp biomicroscopy. This study investigated whether laser in vivo confocal microscopy (IVCM) can aid in the diagnosis of corneal graft rejection by detecting cellular corneal changes that take place after transplantation.

DESIGN

Prospective case-control study.

SUBJECTS

Thirty-eight eyes of 38 patients with penetrating keratoplasty (15 eyes with corneal graft rejection, 23 eyes without rejection) and 9 age-matched normal controls.

METHODS

Laser IVCM was performed in the corneal grafts centrally. The density of immune cells (IC) was assessed for epithelial, sub-epithelial, stromal, and endothelial layers by 2 masked observers. IC density was compared among different groups and correlated to clinical signs and symptoms of corneal graft rejection.

MAIN OUTCOME MEASUREMENTS

Outcome measurement was the IC density in the corneal layers and its associations with the presence of clinical signs and symptoms of corneal graft rejection.

RESULTS

The IC density was significantly different between rejected and non-rejected grafts (P = 0.004) and different from that of normal controls (P = 0.001). Among corneal layers, IC density was significantly higher in rejected grafts than in non-rejected grafts in only the sub-basal (611.54 ± 573.74 vs. 340.61 ± 268.60 cells/mm², respectively; P = 0.049) and endothelial layers (250.62 ± 267.13 vs. 103.47 ± 81.91 cells/mm², respectively; P = 0.001). Patients with decreased best corrected visual acuity, Khodadoust line, and anterior chamber cells demonstrated a significant increase in total IC density (P < 0.05), whereas patients with symptoms of irritation, light sensitivity, and pain revealed a specific increase in IC density in the sub-basal layer (P < 0.05). Patients with ocular pain had higher IC density in the epithelial layer than those without pain (P = 0.03).

CONCLUSIONS

Patients with corneal graft rejection demonstrate a significant increase in corneal immune cells, particularly, in the sub-basal and endothelial layers compared to patients with non-rejected grafts and controls. Although symptoms associated with endothelial rejection demonstrate a general increase in IC, pain, irritation, and light sensitivity are associated with increased IC in the sub-basal layer. Assessment of patients with corneal graft rejection by IVCM may serve as an adjunctive tool in the diagnosis and management of corneal graft rejection.

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.

Prevention and Management of Descemet Membrane Endothelial Keratoplasty Complications

PURPOSE

To describe Descemet membrane endothelial keratoplasty (DMEK) complications and strategies for their prevention and management.

METHODS

Five hundred consecutive eyes with DMEK of 393 patients were reviewed in this retrospective study for intraoperative and postoperative complications up to 2 years and for corresponding management.

RESULTS

Intraoperative challenges (difficult graft unfolding/positioning, high vitreous pressure, iris root hemorrhage, and Descemet membrane remnants) were encountered in 81 eyes (16.2%). Visually significant graft detachment was the main postoperative complication (34 eyes, 6.8%). Graft failure occurred in 8 eyes (1.6%). Other postoperative complications were an increase of intraocular pressure/decompensated glaucoma in 48 eyes (9.6%), significant cataract in 11 of 124 phakic eyes (8.9%), allograft rejection in 7 eyes (1.4%), cystoid macular edema in 5 eyes (1.0%), microbial keratitis in 2 eyes (0.4%), and retinal detachment in 1 eye (0.2%). Different strategies for prevention and management of these complications have been identified.

CONCLUSIONS

DMEK shows acceptable rates of complications up to 2 years after surgery, which can be managed successfully. Anticipation of potential challenges and difficulties may aid in modifying intraoperative strategies for predisposed eyes. This knowledge may further minimize complications, in particular, when performing DMEK for an extended spectrum of corneal endothelial disorders.

Quantitative Assessment of Aqueous Flare After Descemet Membrane Endothelial Keratoplasty for Fuchs Endothelial Dystrophy

PURPOSE

To assess aqueous flare as a measure of subclinical inflammation after Descemet membrane endothelial keratoplasty (DMEK) for Fuchs endothelial dystrophy.

METHODS

In this prospective cross-sectional and longitudinal case series at a tertiary referral center, 173 DMEK eyes of 169 patients and 19 age-matched healthy control eyes were included. Aqueous flare [photon count per millisecond (ph/ms)] was assessed by laser flare photometry at 1 day, 1 week, and 1 month after DMEK in group I (evaluation of postsurgical blood-aqueous barrier recovery; n = 25) and on average 28 (±19) months (range, 3-86 months) after DMEK in group II (evaluation of long-term inflammation; n = 148).

RESULTS

In group I, flare levels decreased from 1 day to 1 week [25.1 (±9.1) ph/ms vs. 13.4 (±4.8) ph/ms; P = 0.003] and remained stable up to 1 month after DMEK [12.1 (±3.2) ph/ms; P = 0.387]. However, average flare at 1 month was higher than that in healthy controls (P < 0.001). The long-term flare value after DMEK (group II) was 9.6 (±4.2) ph/ms and was higher in eyes associated with allograft rejection (n = 6) versus those without rejection [16.7 (±7.8) ph/ms vs. 9.3 (±3.8) ph/ms, respectively, P < 0.001]. All eyes associated with rejection had flare values above 10 ph/ms.

CONCLUSIONS

Aqueous flare after DMEK quickly decreased within the first postoperative month, indicating fast recovery of the blood-aqueous barrier. Long-term flare levels were higher in eyes associated with rejection, suggesting persistent subclinical inflammation. A flare level above 10 ph/ms may be used as a threshold for identifying eyes associated with or at risk of allograft rejection after DMEK.

Influences on rebubble rate in Descemet's membrane endothelial keratoplasty

Purpose

Descemet’s membrane endothelial keratoplasty (DMEK) is a minimally invasive partial corneal transplant procedure used in patients with failing endothelial membranes. This study aims to identify those factors which influence the need for a rebubble of the corneal graft.

Methods

A total of 94 eyes that received DMEK between March 2014 and January 2016 at Vance Thompson Vision were used in the study. Demographic and graft data were collected from the patients and donors, and perioperative statistics of the procedures. A logistical regression was used to compare eyes that did and did not require a rebubble.

Results

Among those characteristics that were included (patient age/sex, donor age/sex, death to processing time, donation to surgery time, death to procurement time, specular cell count density, burping procedure, postoperative day 1 intraocular pressure [IOP], and postoperative week 1 IOP, concurrent phacoemulsification, and how well the Descemet graft was centered), only a lower specular cell count density of the corneal graft, and a graft that was not well-centered correlated with needing a rebubble due to partial graft detachment (p=0.021) and (p=0.023), respectively.

Conclusion

An increased specular cell count density may allow for better placement of the corneal graft by allowing for better unfolding in DMEK procedures. A well-centered graft may decrease postoperative complications by increasing adherence. Additionally, postoperative management of IOP may not affect the rebubble rate, and therefore should be left to the discretion of the provider to determine whether it is necessary.

Sex Chromosome Analysis of Postmortem Corneal Endothelium After Sex-Mismatch Descemet Membrane Endothelial Keratoplasty

PURPOSE

To identify the origin of corneal endothelial cells (host or donor) present on grafts at various time points after Descemet membrane endothelial keratoplasty (DMEK), using fluorescence in situ hybridization (FISH) of sex chromosomes on post mortem corneas with sex mismatch between the donor and host.

METHODS

Corneoscleral buttons of 6 post mortem DMEK eyes of 4 patients, operated for Fuchs endothelial dystrophy, with an average postoperative time of 2.6 (±1.8) years (range, 7 months-4.5 years), of 2.5 (±1.7) years (range, 7 months-4 years), were processed for FISH detection of XX (female) or XY (male)-labeling signals in corneal endothelial cells in the central area of the DMEK graft. Two male patients underwent bilateral DMEK with grafts from female donors, and 2 female patients underwent unilateral DMEK and received a graft from a male donor.

RESULTS

FISH consistently showed the presence of donor endothelial cells across the graft area, with signaling of sex chromosomes opposite to the sex of the host.

CONCLUSIONS

Donor endothelial cells may survive up to 4.5 years after DMEK. If so, the lower incidence of allograft rejection in DMEK may not be explained by early host cell replacement. Potential host cell migration may be limited by donor/recipient cell-cell contact inhibition.

In Vivo Characteristics of Corneal Endothelium/Descemet Membrane Complex for the Diagnosis of Corneal Graft Rejection

PURPOSE

To evaluate the utility of endothelial/Descemet membrane complex (En/DM) characteristics in diagnosing corneal graft rejection.

DESIGN

Diagnostic reliability study.

METHODS

One hundred thirty-nine eyes (96 corneal grafts post penetrating keratoplasty or Descemet stripping automated endothelial keratoplasty: 40 clear, 23 actively rejecting, 24 rejected, and 9 nonimmunologic failed grafts; along with 43 age-matched control eyes) were imaged using high-definition optical coherence tomography. Images were used to describe En/DM and measure central corneal thickness (CCT) and central En/DM thickness (DMT). En/DM rejection index (DRI) was computed to detect the relative En/DM thickening to the entire cornea.

RESULTS

In actively rejecting grafts, DMT and DRI were significantly greater than controls and clear grafts (28, 17, and 17 μm and 1.5, 1 and 1, respectively; P < .001). Rejected grafts had the highest DMT and DRI compared to all groups (59 μm and 2.1; P < .001). DMT and DRI showed excellent accuracy, significantly better than that of CCT, in differentiating actively rejecting from clear grafts (100% and 96% sensitivity; 92.5% and 92.5% specificity), actively rejecting from rejected grafts (88% and 83% sensitivity; 91% and 83% specificity), and nonimmunologic failed from rejected grafts (100% and 100% sensitivity; 88% and 100% specificity). DMT correlated significantly with rejection severity (P < .001).

CONCLUSIONS

In corneal grafts, in vivo relative thickening of the En/DM is diagnostic of graft rejection as measured by DMT and DRI. These indices have excellent accuracy, sensitivity, and specificity in detecting graft immunologic status, superior to CCT. DMT is a quantitative index that correlates accurately with the severity of rejection.

360-Degree Scheimpflug Imaging to Predict Allograft Rejection After Descemet Membrane Endothelial Keratoplasty

PURPOSE

To describe the use of 360-degree Scheimpflug imaging as a diagnostic tool for detection and documentation of subtle corneal changes preceding upcoming allograft rejection after Descemet membrane endothelial keratoplasty (DMEK).

METHODS

A total of 17 eyes (16 patients) were diagnosed with clinically manifest allograft rejection 2 to 42 months after DMEK. 360-degree Scheimpflug images of consecutive follow-up examinations (from 3-60 mo) of "asymptomatic" eyes before, during, and after rejection were retrospectively analyzed, to determine which abnormalities could be detected before allograft rejection became clinically manifest. The images were compared with DMEK control eyes (without rejection episode).

RESULTS

Scheimpflug images at the time of rejection showed keratic precipitates as distinct retrocorneal nodular elevations and/or a significant increase in pachymetry of ≥7%. More subtle changes could be identified retrospectively in 9/17 eyes (53%) on an average at 8 (±5) months before rejection became clinically manifest; in all eyes, these subtle changes were not recognized at routine slit-lamp examinations by various ophthalmologists as inflammatory changes heralding allograft rejection. Secondary graft failure occurred in 4/17 eyes (24%). None of the control eyes showed relevant abnormalities with Scheimpflug imaging.

CONCLUSIONS

By screening the posterior corneal surface with 360-degree Scheimpflug imaging, subtle inflammatory retrocorneal deposits can be detected and recorded during consecutive follow-up visits. Hence, Scheimpflug imaging may have the potential to become a diagnostic tool for early detection of upcoming allograft rejection in asymptomatic DMEK eyes, that is, before the immune response becomes clinically manifest and before substantial endothelial cell damage occurs.

Midterm Results of Descemet Membrane Endothelial Keratoplasty: 4 to 7 Years Clinical Outcome

PURPOSE

To evaluate the midterm outcomes of Descemet membrane endothelial keratoplasty (DMEK) up to 4-7 years postoperatively.

DESIGN

Retrospective, consecutive interventional case series.

METHODS

A total of 250 consecutive eyes of 209 patients who underwent DMEK at our institute and had potentially at least 4 years of follow-up. Main outcome measures were best-corrected visual acuity (BCVA), endothelial cell density (ECD), central corneal thickness (CCT), graft survival rate, and postoperative complications.

RESULTS

At 6 months postoperatively, 73% of the eyes reached a BCVA of ≥20/25 (0.8) and 44% ≥20/20 (1.0), and remained stable up to 7 years (P = .7114). ECD dropped by 33.9% in the first 6 months, and then declined by a yearly rate of 9.0%. CCT did not show a significant change after 6 months up to 7 years (P = .8447). The cumulative graft survival rate at 4 and 7 years was 0.96 (95% confidence interval [0.93, 0.99]). Rebubbling procedures were performed in 4.4% of eyes, all within the first 6 postoperative months. Repeat transplantations were performed in 15.2% of cases to manage greater than one third graft detachment (11.6%), primary graft failure (1.6%), or secondary graft failure (2.0%), with the majority (79%) of repeat transplantations performed within the first year. After 6 months, the main complications were allograft rejection (2.4%) and secondary graft failure (2.0%).

CONCLUSIONS

The visual acuity level achieved at 6 months after DMEK may remain stable up to at least 4-7 years; ECD shows a constant, slow decrease; and complications after the first 6 months occur in <5% of cases.

Long-lasting corneal endothelial graft rejection successfully reversed after dexamethasone intravitreal implant

Graft rejection is the most significant complication corneal transplantation and the leading indication for overall corneal transplantation. Corticosteroid therapy represents the mainstay of graft rejection treatment; however, the optimal route of administration of corticosteroid remains uncertain. We report herein for the first time the multimodal imaging of a case of long-lasting corneal endothelial graft rejection successfully reversed 3 months after dexamethasone intravitreal implant. A 29-year-old Asian female presented with a long-lasting corneal endothelial graft rejection in her left phakic eye. She underwent penetrating keratoplasty for advanced keratoconus 24 months before presentation. Hourly dexamethasone eyedrops, daily intravenous methylprednisolone, and one parabulbar injection of methylprednisolone acetate were administered during the 5 days of hospitalization. However, the clinical picture remained approximately unchanged despite therapy. By mutual agreement, we opted for the off-label injection of dexamethasone 0.7 mg intravitreal implant in order to provide therapeutic concentrations of steroid for a period of ~6 months. No other concomitant therapies were prescribed to the patient. Visual acuity measurement, slit lamp biomicroscopy, anterior segment photography, confocal microscopy, anterior segment optical coherence tomography, laser cell flare meter, intraocular pressure measurement, and ophthalmoscopy were performed monthly for the first postoperative 6 months. Three months after injection, both clinical and subclinical signs of rejection disappeared with a full recovery of visual acuity to 20/30 as before the episode. Currently, at the 12-month follow-up visit, the clinical picture remains stable without any sign of rejection, recurrence, or graft failure. Dexamethasone intravitreal implant seems to be a new potential effective treatment for corneal graft rejection, particularly in case of poor compliance or lack of response to conventional treatment. In addition, it could be especially useful in diabetic patients unable to receive systemic steroids.

Descemet membrane endothelial keratoplasty

Descemet membrane endothelial keratoplasty (DMEK) allows for selective replacement of damaged endothelial cells, using only donor Descemet's membrane with endothelium. However, early adoption by corneal surgeons has been limited (illustrated by graft registry reports: 0.7% all corneal transplants in the USA; 0.4% in Australia for 2011) due to challenges in donor preparation and surgical technique. Recently, innovative donor preparation techniques may improve availability of pre-stripped DMEK donors from eye banks. The refinement of donor insertion and manipulation techniques has also improved outcomes and reduced graft detachment rates-still, the most common postoperative complication following DMEK. Randomised studies are needed to compare clinical practices and surgeon preferences, such as intraoperative use of long-acting gas, early versus late intervention of graft detachments and postoperative steroid management. A review of current literature reveals that most publications to date are reports from similar study cohorts by surgeons who pioneered and advocate this technique. Thus, more long-term clinical studies in other tertiary centres are required in order to confirm if the purported advantages of DMEK such as improved visual outcomes and reduced graft rejection are replicable among most corneal surgeons.