UV light-mediated corneal crosslinking as (lymph)angioregressive pretreatment to promote graft survival after subsequent high-risk corneal transplantation (CrossCornealVision): protocol for a multicenter, randomized controlled trial.

BACKGROUND: Good vision highly depends on the transparency of the cornea, which is the "windscreen" of the eye. In fact, corneal blindness due to transparency loss is the second most common cause of blindness worldwide, and corneal transplantation is the main cure. Importantly, the cornea is normally avascular but can secondarily be invaded by pathological (blood and lymphatic) vessels due to severe inflammation, and the survival prognosis of a corneal graft mainly depends on the preoperative vascular condition of the recipient's cornea. Whereas transplants placed into avascular recipient beds enjoy long-term survival rates of > 90%, survival rates significantly decrease in pathologically pre-vascularized, so-called high-risk recipients, which account for around 10% of all performed transplants in Germany and > 75% in lower and middle-income countries worldwide. METHODS: This parallel-grouped, open-randomized, multicenter, prospective controlled exploratory investigator-initiated trial (IIT) intends to improve graft survival by preconditioning pathologically vascularized recipient corneas by (lymph)angioregressive treatment before high-risk corneal transplantation. For this purpose, corneal crosslinking (CXL) will be used, which has been shown to potently regress corneal blood and lymphatic vessels. Prior to transplantation, patients will be randomized into 2 groups: (1) CXL (intervention) or (2) no pretreatment (control). CXL will be repeated once if insufficient reduction of corneal neovascularization should be observed. All patients (both groups) will then undergo corneal transplantation. In the intervention group, remaining blood vessels will be additionally regressed using fine needle diathermy (on the day of transplantation). Afterwards, the incidence of graft rejection episodes will be evaluated for 24 months (primary endpoint). Overall graft survival, as well as regression of corneal vessels and/or recurrence, among other factors, will be analyzed (secondary endpoints). DISCUSSION: Based on preclinical and early pilot clinical evidence, we want to test the novel concept of temporary (lymph)angioregressive pretreatment of high-risk eyes by CXL to promote subsequent corneal graft survival. So far, there is no evidence-based approach to reliably improve graft survival in the high-risk corneal transplantation setting available in clinical routine. If successful, this approach will be the first to promote graft survival in high-risk transplants. It will significantly improve vision and quality of life in patients suffering from corneal blindness. TRIAL REGISTRATION: ClinicalTrials.gov NCT05870566. Registered on 22 May 2023.

The role of the osmosensitive transcription factor NFAT5 in corneal edema resorption after injury.

The osmosensitive transcription factor nuclear factor of activated T cells 5 (NFAT5; or tonicity-responsive enhancer binding protein; TonEBP) plays a key role in macrophage-driven regulation of cutaneous salt and water balance. In the immune-privileged and transparent cornea, disturbances in fluid balance and pathological edema result in corneal transparency loss, which is one of the main causes of blindness worldwide. The role of NFAT5 in the cornea has not yet been investigated. We analyzed the expression and function of NFAT5 in naive corneas and in an established mouse model of perforating corneal injury (PCI), which causes acute corneal edema and transparency loss. In uninjured corneas, NFAT5 was mainly expressed in corneal fibroblasts. In contrast, after PCI, NFAT5 expression was highly upregulated in recruited corneal macrophages. NFAT5 deficiency did not alter corneal thickness in steady state; however, loss of NFAT5 led to accelerated resorption of corneal edema after PCI. Mechanistically, we found that myeloid cell-derived NFAT5 is crucial for controlling corneal edema, as edema resorption after PCI was significantly enhanced in mice with conditional loss of NFAT5 in the myeloid cell lineage, presumably due to increased pinocytosis of corneal macrophages. Collectively, we uncovered a suppressive role for NFAT5 in corneal edema resorption, thereby identifying a novel therapeutic target to combat edema-induced corneal blindness.

The novel role of lymphatic vessels in the pathogenesis of ocular diseases.

Historically, the eye has been considered as an organ free of lymphatic vessels. In recent years, however, it became evident, that lymphatic vessels or lymphatic-like vessels contribute to several ocular pathologies at various peri- and intraocular locations. The aim of this review is to outline the pathogenetic role of ocular lymphatics, the respective molecular mechanisms and to discuss current and future therapeutic options based thereon. We will give an overview on the vascular anatomy of the healthy ocular surface and the molecular mechanisms contributing to corneal (lymph)angiogenic privilege. In addition, we present (i) current insights into the cellular and molecular mechanisms occurring during pathological neovascularization of the cornea triggered e.g. by inflammation or trauma, (ii) the role of lymphatic vessels in different ocular surface pathologies such as dry eye disease, corneal graft rejection, ocular graft versus host disease, allergy, and pterygium, (iii) the involvement of lymphatic vessels in ocular tumors and metastasis, and (iv) the novel role of the lymphatic-like structure of Schlemm's canal in glaucoma. Identification of the underlying molecular mechanisms and of novel modulators of lymphangiogenesis will contribute to the development of new therapeutic targets for the treatment of ocular diseases associated with pathological lymphangiogenesis in the future. The preclinical data presented here outline novel therapeutic concepts for promoting transplant survival, inhibiting metastasis of ocular tumors, reducing inflammation of the ocular surface, and treating glaucoma. Initial data from clinical trials suggest first success of novel treatment strategies to promote transplant survival based on pretransplant corneal lymphangioregression.

Different Murine High-Risk Corneal Transplant Settings Vary Significantly in Their (Lymph)angiogenic and Inflammatory Cell Signatures.

Purpose: Pathologic conditions in the cornea, such as transplant rejection or trauma, can lead to corneal neovascularization, creating a high-risk environment that may compromise subsequent transplantation. This study aimed to evaluate the impact of different types of corneal injury on hemangiogenesis (HA), lymphangiogenesis (LA) and immune cell pattern in the cornea. Methods: We used five different corneal injury models, namely, incision injury, alkali burn, suture placement, and low-risk keratoplasty, as well as high-risk keratoplasty and naïve corneas as control. One week after incision and 2 weeks after all other different injuries, corneal HA and LA were quantified by morphometric analysis. In addition, immune cell patterns of the whole cornea and the recipient rim were analyzed by immunohistochemistry. Immune cells in the draining lymph nodes (dLNs) were quantified by flow cytometry. Results: Different types of corneal injury caused significantly different HA and LA responses (both P < 0.0001). The infiltration of corneal macrophages, dendritic cells, neutrophils, major histocompatibility complex (MHC) II+ cells, CD4+ T cells, and CD8+ T cells varied significantly in different high-risk settings (all P < 0.0001). Both the expression of MHC II on macrophages (P = 0.0005) and the frequency of MHC II+ dendritic cells (P = 0.0014) in the draining lymph nodes were significantly different across the various high-risk scenarios. Conclusions: Murine high-risk settings caused by different underlying pathologies vary significantly in their (lymph)angiogenic and inflammatory cell patterns. Therefore, anti(lymph)angiogenic or immunomodulatory strategies to prevent and/or treat immune responses after subsequent corneal transplantation may need to be customized according to their immune-vascular "signatures."

Outcomes of deep anterior lamellar keratoplasty and penetrating keratoplasty in keratoconic eyes with and without previous hydrops.

PURPOSE: The study aims to compare outcomes after deep anterior lamellar keratoplasty (DALK) and penetrating keratoplasty (PK) in keratoconic eyes with or without previous hydrops. METHODS: Retrospective analysis of 211 eyes who received PK (group 1, n = 74 [history of hydrops: n = 33]) or DALK (group 2, n = 137 [history of hydrops: n = 9]) from 2012 to 2019 at the Department of Ophthalmology, University of Cologne, Germany. Analysis included best spectacle-corrected visual acuity (BSCVA), complications, immune reactions, graft survival and keratometry, and subgroup analyses for subjects with or without previous hydrops. RESULTS: Follow-up was 34.0 ± 23.6 months in group 1 and 30.7 ± 22.5 months in group 2. No significant difference was found in the course of BSCVA between groups 1 and 2 (p = 0.182) and in postoperative BSCVA between eyes with and without previous hydrops, regardless of the surgical method (p = 0.768). Endothelial immune reactions occurred exclusively in group 1 and did not occur more frequently in eyes with previous hydrops (p = 0.377). A higher risk of complications for eyes with previous hydrops was observed (p = 0.022). There was no difference in astigmatism and maximum keratometry (Kmax) preoperatively and postoperatively between eyes with and without history of hydrops. CONCLUSION: The prognosis for visual outcome after keratoplasty including visual acuity, astigmatism, and Kmax for keratoconic eyes with previous hydrops is as good as for keratoconic eyes without previous hydrops, irrespective of the surgical method. However, eyes after hydrops seem to have an increased risk of complications.

Lymphatic Trafficking in the Eye: Modulation of Lymphatic Trafficking to Promote Corneal Transplant Survival.

(Lymph)angiogenesis into the cornea prior to and after corneal transplantation is a critical risk factor for allograft rejection. Lymphatic vessels even more than blood vessels seem important in mediating immune responses, as they facilitate allograft sensitization in the draining lymph nodes. Thus, the concept of modulating lymphatic trafficking to promote corneal graft survival seems promising. A variety of approaches has been developed to inhibit progressive lymphangiogenesis in experimental settings. Recently, additionally to pharmacological approaches, clinically available techniques such as UVA-based corneal collagen crosslinking and fine needle diathermy were reported to be effective in regressing lymphatic vessels and to experimentally promote graft survival. Clinical pilot studies also suggest the efficacy of blocking antigen presenting cell trafficking to regional lymph nodes by regressing corneal lymphatic vessels to enhance allograft survival in high-risk eyes. In this article, we will give an overview of current strategies to modulate lymphatic trafficking with a special focus on recently reported strategies, which may be easy to translate into clinical practice. This novel concept of temporary, pretransplant regression of lymphatic vessels at the site of transplantation to promote subsequent corneal transplant survival ("lymphangioregressive preconditioning") may also be applicable to other transplantation sites later.

Cutting Edge: Novel Treatment Options Targeting Corneal Neovascularization to Improve High-Risk Corneal Graft Survival.

PURPOSE: Corneal neovascularization is an important risk factor for graft rejection after keratoplasty, although its role in posterior lamellar keratoplasty is not yet well defined. The aim of this work was to describe clinically available approaches that target corneal neovascularization preoperatively to improve graft survival after subsequent penetrating keratoplasty (PK) and to present findings on Descemet membrane endothelial keratoplasty (DMEK) in eyes with neovascularization. METHODS: Recent work on the use of anti-vascular endothelial growth factor agents, fine needle diathermy (FND), and corneal collagen crosslinking (CXL) to regress corneal neovascularization before PK is summarized. Furthermore, studies that have investigated the outcome of DMEK in vascularized eyes are presented. RESULTS: Pretreatment of recipient corneas with FND combined with anti-vascular endothelial growth factor agents is an effective method to reduce long-standing corneal neovascularization and results in relatively low rejection rates after subsequent high-risk PK. Peripheral CXL also seems to be a potent method to regress corneal neovascularization, although data on the impact of pretransplant CXL on long-term graft survival are not yet available. There are only limited data on graft rejection rates after DMEK in vascularized eyes, but initial studies indicate that DMEK seems to be a viable therapeutic option when no stromal scars are present. Furthermore, preexisting stromal neovascularization seems to regress after high-risk DMEK. CONCLUSIONS: Several angioregressive strategies to treat corneal neovascularization before PK have entered the clinic with promising initial results, which warrants larger trials with longer follow-up. Studies will also have to define the precise role of preexisting corneal neovascularization in high-risk DMEK.

Comparison of Mini-DMEK versus predescemetal sutures as treatment of acute hydrops in keratoconus.

PURPOSE: To compare two surgical treatment options for acute corneal hydrops in keratoconus: Mini-DMEK versus predescemetal sutures. METHODS: Sixteen patients were treated by either Mini-Descemet membrane endothelial keratoplasty (Mini-DMEK) (n = 7, group 1) or predescemetal sutures (n = 9, group 2) early after onset of acute hydrops. Visual acuity, maximum corneal thickness (SD-OCT) in the affected oedematous area, complications and recurrence rates were retrospectively compared between both groups. Measurements were taken immediately preoperatively as well as 1 day, 1 week and 1 month postoperatively (Table 1). RESULTS: Both groups showed reductions in corneal thickness and increased visual acuity shortly after surgery. In group 1 (average age 33 years ± 7 years), the best corrected visual acuity (BCVA) increased from logMAR 1.65 ± 0.7 before Mini-DMEK to logMAR 0.93 ± 0.6 30 days after Mini-DMEK (p = 0.046). During that period, maximum corneal thickness decreased from 1159 ± 338 µm before surgery to 531 ± 75 µm after Mini-DMEK (p = 0.046). Patients from group 2 (average age 34 ± 10 years) had a BCVA of logMAR 1.59 ± 0.8 which increased to logMAR 0.97 ± 0.5 (p = 0.014) 30 days after surgery. At the same time, the preoperative maximum corneal thickness decreased from 1439 ± 272 µm to 476 ± 162 µm (p = 0.014). There was no difference in corneal thickness or BCVA one month after the surgical intervention between both groups (p = 0.394 and p = 0.871). CONCLUSIONS: Both techniques, Mini-DMEK and predescemetal sutures, are effective in the treatment of an acute hydrops in keratoconus. Mini-DMEK appears to be beneficial in large DM tears.

Macrophage-Mediated Tissue Vascularization: Similarities and Differences Between Cornea and Skin.

Macrophages are critical mediators of tissue vascularization both in health and disease. In multiple tissues, macrophages have been identified as important regulators of both blood and lymphatic vessel growth, specifically following tissue injury and in pathological inflammatory responses. In development, macrophages have also been implicated in limiting vascular growth. Hence, macrophages provide an important therapeutic target to modulate tissue vascularization in the clinic. However, the molecular mechanisms how macrophages mediate tissue vascularization are still not entirely resolved. Furthermore, mechanisms might also vary among different tissues. Here we review the role of macrophages in tissue vascularization with a focus on their role in blood and lymphatic vessel formation in the barrier tissues cornea and skin. Comparing mechanisms of macrophage-mediated hem- and lymphangiogenesis in the angiogenically privileged cornea and the physiologically vascularized skin provides an opportunity to highlight similarities but also tissue-specific differences, and to understand how macrophage-mediated hem- and lymphangiogenesis can be exploited for the treatment of disease, including corneal wound healing after injury, graft rejection after corneal transplantation or pathological vascularization of the skin.

Corneal Crosslinking to Regress Pathologic Corneal Neovascularization Before High-Risk Keratoplasty.

PURPOSE: Corneal neovascularization is the main risk factor for graft rejection after high-risk penetrating keratoplasty (PK). Corneal crosslinking (CXL) has been shown to regress pathological corneal blood and lymphatic vessels and to reduce the risk of graft rejection after high-risk PK experimentally in mice. The aim of this work was to analyze whether CXL is also able to regress corneal neovascularization in patients and is a safe procedure in the context of high-risk PK. METHODS: This retrospective case series included 5 patients with progressive corneal neovascularization and the need for high-risk PK because of graft rejection and/or keratitis that received CXL and PK between April 2019 and January 2020. CXL was performed before or in combination with PK and the effect of CXL on corneal neovascularization was assessed morphometrically on slit-lamp images. Patients were followed up to determine the incidence of adverse effects and graft rejection. RESULTS: In 1 case, peripheral corneal CXL was performed first as a single procedure, followed by an additional peripheral CXL procedure combined with PK. In all other cases, peripheral CXL was directly combined with PK. No intraoperative or postoperative complications were observed. Peripheral CXL resulted in a reduction of corneal neovascularization (mean reduction of 70.5% ± 22.7%). Revascularization was not observed. All transplants remained clear and without immune reactions (mean follow-up 16.4 ± 14.9 weeks, range 4-42 weeks). CONCLUSIONS: CXL is able to reduce pathological corneal neovascularization and might therefore be a novel treatment option to improve graft survival after high-risk PK.

New Technologies in Clinical Trials in Corneal Diseases and Limbal Stem Cell Deficiency: Review from the European Vision Institute Special Interest Focus Group Meeting.

To discuss and evaluate new technologies for a better diagnosis of corneal diseases and limbal stem cell deficiency, the outcomes of a consensus process within the European Vision Institute (and of a workshop at the University of Cologne) are outlined. Various technologies are presented and analyzed for their potential clinical use also in defining new end points in clinical trials. The disease areas which are discussed comprise dry eye and ocular surface inflammation, imaging, and corneal neovascularization and corneal grafting/stem cell and cell transplantation. The unmet needs in the abovementioned disease areas are discussed, and realistically achievable new technologies for better diagnosis and use in clinical trials are outlined. To sum up, it can be said that there are several new technologies that can improve current diagnostics in the field of ophthalmology in the near future and will have impact on clinical trial end point design.

Descemet Membrane Endothelial Keratoplasty in Vascularized Eyes: Outcome and Effect on Corneal Neovascularization.

PURPOSE: To report the outcomes after Descemet membrane endothelial keratoplasty (DMEK) in vascularized eyes. METHODS: Consecutive cases of DMEK in vascularized eyes (involving ≥2 vascularized quadrants) were selected from a prospective database. Best corrected visual acuity, endothelial cell density (ECD), central corneal thickness, corneal transplant rejection episode, graft survival, and area of neovascularization (quantified using image analysis software) were evaluated. RESULTS: In this study, 24 eyes of 24 patients were selected [mean age, 65.0 years; mean follow-up duration, 14.8 months (6-36 months)], which consists of 14 vascularized eyes after failed penetrating keratoplasty and 10 vascularized eyes with bullous keratopathy. Best corrected visual acuity improved from 1.60 ± 1.02 LogMAR preoperatively to 0.47 ± 0.37 LogMAR 12 months postoperatively (P < 0.001). Central corneal thickness decreased from 824 ± 193 µm preoperatively to 544 ± 48 µm 12 months postoperatively (P = 0.001). The donor ECD decreased from 2272 ± 723 cells/mm2 preoperatively to 1570 ± 279 cells/mm2 12 months postoperatively. The total loss of ECD at the last visit was 40.7% ± 13.0%. Eight of 24 eyes (33.3%) required rebubbling, which resulted in final attachment. The corneal neovascularization area significantly regressed from 4.68% ± 3.26% preoperatively to 2.28% ± 1.58% (n = 18, P = 0.021). Corneal transplant rejection episodes occurred in 1 eye of 24 patients (4.2%). There was no primary graft failure. CONCLUSIONS: DMEK is a feasible option to treat endothelial dysfunction in vascularized eyes.

VEGF TrapR1R2 Suspended in the Semifluorinated Alkane F6H8 Inhibits Inflammatory Corneal Hem- and Lymphangiogenesis.

Purpose: Semifluorinated alkanes (SFAs) are used at the ocular surface as lubricants or vehicles for drugs. The purpose of this study was to test the effect of vascular endothelial growth factor (VEGF) TrapR1R2 suspended in the SFA perfluorohexyloctane (Trap/F6H8) on corneal neovascularization. Methods: Suture placement was used to induce inflammatory corneal neovascularization in mice. Treatment groups were: Trap/F6H8, VEGF TrapR1R2 as aqueous formulation dissolved in phosphate buffer (Trap), F6H8, and phosphate buffer (controls). Eye drops were applied 3×/daily for 2 weeks. Afterward, corneas were stained with CD31 and LYVE-1 to analyze corneal hem- and lymphangiogenesis. To investigate the effect of on inflammatory cell recruitment, corneal CD45+ cells were quantified. In addition, epithelial wound closure after debridement was assessed by corneal fluorescein staining. Results: Trap/F6H8 was as effective as Trap in inhibiting corneal hemangiogenesis and lymphangiogenesis after 2 weeks of treatment. After 3 days of treatment, Trap/F6H8 was even more effective than Trap in inhibiting corneal hemangiogenesis. Both treatment groups (Trap/F6H8 and Trap) significantly reduced corneal CD45+ cell recruitment. Epithelial closure after debridement was unaffected by Trap/F6H8 or Trap. Conclusions: In this study, we demonstrate that F6H8 is a potential carrier for VEGF TrapR1R2 to topically treat corneal neovascularization. Our findings might open new treatment avenues for local anti-angiogenic therapy at the cornea, as F6H8 is already approved for the usage at the ocular surface. Translational Relevance: With this study we show for the first time that SFAs can serve as carriers for anti-angiogenic drugs at the ocular surface.

TRIM21 Is Targeted for Chaperone-Mediated Autophagy during Salmonella Typhimurium Infection.

Salmonella enterica serovar Typhimurium (S Typhimurium) is a Gram-negative bacterium that induces cell death of macrophages as a key virulence strategy. We have previously demonstrated that the induction of macrophage death is dependent on the host's type I IFN (IFN-I) response. IFN-I signaling has been shown to induce tripartite motif (TRIM) 21, an E3 ubiquitin ligase with critical functions in autoimmune disease and antiviral immunity. However, the importance and regulation of TRIM21 during bacterial infection remains poorly understood. In this study, we investigated the role of TRIM21 upon S Typhimurium infection of murine bone marrow-derived macrophages. Although Trim21 expression was induced in an IFN-I-dependent manner, we found that TRIM21 levels were mainly regulated posttranscriptionally. Following TLR4 activation, TRIM21 was transiently degraded via the lysosomal pathway by chaperone-mediated autophagy (CMA). However, S Typhimurium-induced mTORC2 signaling led to phosphorylation of Akt at S473, which subsequently impaired TRIM21 degradation by attenuating CMA. Elevated TRIM21 levels promoted macrophage death associated with reduced transcription of NF erythroid 2-related factor 2 (NRF2)-dependent antioxidative genes. Collectively, our results identify IFN-I-inducible TRIM21 as a negative regulator of innate immune responses to S Typhimurium and a previously unrecognized substrate of CMA. To our knowledge, this is the first study reporting that a member of the TRIM family is degraded by the lysosomal pathway.

Topical VEGF-C/D Inhibition Prevents Lymphatic Vessel Ingrowth into Cornea but Does Not Improve Corneal Graft Survival.

Vascular endothelial growth factor-C/D (VEGF-C/D) regulates lymphangiogenesis. Ingrowth of lymphatic vessels is negatively associated with corneal transplantation success. In this study, we therefore analyzed the effect local blockade of VEGF-C/D has on inflamed corneas. We used the murine model of suture-induced neovascularization and subsequent high-risk corneal transplantation. Mice were treated with a VEGF-C/D trap prior to transplantation. Topical inhibition of VEGF-C/D significantly reduced lymphatic vessel ingrowth, but increased Macrophage numbers in the cornea. Furthermore, corneal transplantation success was not improved by the topical application of the compound. This study demonstrates that local VEGF-C/D inhibition is insufficient to increases corneal transplantation success, likely due to interaction with immune cells.

Effect of Iris Color on the Outcome of Descemet Membrane Endothelial Keratoplasty.

PURPOSE: To explore the impact of iris color on the outcome of Descemet membrane endothelial keratoplasty (DMEK). METHODS: Consecutive cases of Fuchs endothelial dystrophy after DMEK were retrospectively analyzed from the prospective Cologne DMEK database between 2011 and 2017 at the University of Cologne, Germany. Iris pictures were graded by color into blue, green, or brown and compared regarding outcome parameters including best-corrected visual acuity (converted to logarithm of the minimal angle of resolution), central corneal thickness, endothelial cell density (ECD), each at preoperative (baseline) and postoperative 12 months, rebubbling rates, cystoid macular edema (CME), and immune rejections after surgery. RESULTS: One thousand one hundred six eyes of 814 patients were included in this study that consisted of 354 blue eyes, 418 green eyes, and 244 brown eyes. There was no significant correlation between iris color and any parameter (best corrected visual acuity; P = 0.064 at preoperatively, P = 0.959 at 12 months) (ECD; P = 0.158 preoperatively, P = 0.859 at 12 months) (central corneal thickness; P = 0.148 preoperatively, P = 0.252 at 12 months). The loss of ECD at 12 months after surgery was 37.2% ± 1.0% in blue eyes, 37.2% ± 0.9% in green eyes, and 37.2% ± 1.2% in brown eyes (P = 0.999). Immune rejections were 1.7%, 2.9%, and 0.8% (P = 0.168) in blue, green, and brown eyes, respectively. Rebubbling rates and CME incidence were similar in each group (P = 0.129, and P = 0.552 respectively). CONCLUSIONS: The iris color has no significant impact on the outcome after DMEK. Thus, DMEK can be applied effectively, regardless of the iris color.

Outcome of Descemet Membrane Endothelial Keratoplasty Using Corneas from Donors ≥80 Years of Age.

PURPOSE: The purpose of this study was to investigate whether corneas from donors ≥80 years old are suitable for Descemet membrane endothelial keratoplasty (DMEK). DESIGN: Retrospective, comparative, interventional case series. METHODS: Records of 1,765 consecutive DMEKs were reviewed and matched with corresponding donor tissue data. Older donors (≥80 years of age) were compared to younger donors (<80 years). Outcome measurements in DMEK recipients included best spectacle-corrected visual acuity (BSCVA), endothelial cell density (ECD), central corneal thickness (CCT) at 3 and 6 months and at 1, 2, and 3 years' follow-up and re-bubbling rates. RESULTS: Of 1,748 DMEKs, 284 (16.2%) were performed with older donor lamellae (mean donor age, 83.96 ± 3.19 years; range, 80-94 years) and 1,464 (83.7%) with younger donor tissue (mean donor age, 65.27 ± 9.57 years; range, 17-79). BSCVA results were comparable for all postoperative time points. CCT results for younger donors were more favorable in the early postoperative course (P < 0.001 at 6 months; and P < 0.001 at 1 year), whereas mid-term results were comparable in both groups. ECD values were significantly higher in donors <80 years of age preoperatively and during the first 2 postoperative years (P ≤ 0.024). Overall re-bubbling rates were comparable in both groups. CONCLUSIONS: Older donors, ≥80 to 94 years of age, seem to produce comparable mid-term functional results following DMEK surgery compared to younger donors. The use of corneas from donors aged ≥80 for DMEK surgery may therefore be a promising approach to counteract global donor shortage.

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.