Donor age and factors related to endothelial cell loss 10 years after penetrating keratoplasty: Specular Microscopy Ancillary Study

Descemet Membrane Endothelial Keratoplasty: 10-Year Cell Loss and Failure Rate Compared With Descemet Stripping Endothelial Keratoplasty and Penetrating Keratoplasty

PURPOSE

The aim of this study was to assess long-term endothelial cell loss (ECL) and graft failure with Descemet membrane endothelial keratoplasty (DMEK) and Descemet stripping endothelial keratoplasty (DSEK) versus penetrating keratoplasty (PK) performed for the same indications (primarily Fuchs dystrophy and pseudophakic corneal edema) in the Cornea Donor Study.

METHODS

This retrospective study included consecutive primary DMEK (529 recipients, 739 eyes) and DSEK cases (585 recipients, 748 eyes) with 1 or more endothelial cell density (ECD) measurements at 6 months to 16 years. Main outcomes were ECD, longitudinal ECL, and graft failure.

RESULTS

Between 6 months and 8 years the ECD declined linearly by approximately 118 cells/mm2/yr after DMEK and 112 cells/mm2/yr after DSEK. Beyond 8 years postoperatively the rate of decline slowed substantially. Selective dropout from graft failure did not significantly affect the ECD trend. At 10 years, median ECL (interquartile range) was 63% (45, 73) with DMEK, 68% (48, 78) with DSEK, and 76% (70, 82) with PK (P = 0.01 DMEK vs. DSEK, P <0.001 DMEK vs. PK, and P < 0.001 DSEK vs. PK). The proportion of surviving grafts with 10-year ECD <500 cells/mm2 was 1.4% with DMEK, 7.3% with DSEK, and 23.9% with PK. The cumulative risk of graft failure between 6 months and 10 years was 5% with DMEK, 11% with DSEK, and 19% with PK (P < 0.001).

CONCLUSIONS

Compared with PK and DSEK, DMEK had significantly lower ECL and significantly lower risk of secondary graft failure through 10 years.

Fusogenic liposome-coated nanoparticles for rapid internalization into donor corneal endothelial tissue to enable prophylaxis before transplantation

Cold stress (hypothermia) during storage and cytokine stress due to acute allograft rejection adversely affect the donor corneal endothelium in the short term. Pharmacological pre-treatment (before transplantation) of the donor corneal endothelium or cells (propagated in vitro for cell injection therapy) with microtubule stabilizers, cold stress protectants, and other molecules is an attractive strategy to tackle damage caused by hypothermia and cytokine stress. These molecules can be delivered intracellularly to the donor corneal endothelium or cells at controlled rates for desired periods and with one-time administration using nanoparticles. However, the death-to-preservation time of donor corneas of more than 4 to 6 h significantly decreases endothelial cell density and increases the risk of microbial contamination. Therefore, we have developed fusogenic liposome-coated nanoparticles for rapid internalization of nanoparticles into cultured corneal endothelial cells and ex vivo corneal endothelial tissue. Here, we have shown that the fusogenic liposome-coated nanoparticles have the intrinsic ability to efficiently and rapidly internalize into cultured corneal endothelial cells and ex vivo corneal tissue within 3 h by possibly fusing with the cell membrane and bypassing the endocytic pathway. Lactate dehydrogenase assay showed that the internalized fusogenic liposome-coated nanoparticles did not cause cytotoxicity in endothelial cells associated with the ex vivo cornea for at least up to 2 days. Thus, fusogenic liposome-coated nanoparticles have great potential as a platform for engineering cells and endothelial tissue of donor corneas to facilitate prophylactic drug delivery during storage and after transplantation.

Integrated Analysis of Transcriptome and Proteome of the Human Cornea and Aqueous Humor Reveal Novel Biomarkers for Corneal Endothelial Cell Dysfunction

Earlier studies have reported that elevated protein levels in the aqueous humor (AH) are associated with corneal endothelial cell dysfunction (CECD), but the details of the underlying mechanism as well as specific biomarkers for CECD remain elusive. In the present study, we aimed to identify protein markers in AH directly associated with changes to corneal endothelial cells (CECs), as AH can be easily obtained for analysis. We carried out an in-depth proteomic analysis of patient-derived AH as well as transcriptomic analysis of CECs from the same patients with bullous keratopathy (BK) resulting from CECD. We first determined differentially expressed genes (DEGs) and differentially expressed proteins (DEPs) from CECs and AH in CECD, respectively. By combining transcriptomic and proteomic analyses, 13 shared upregulated markers and 22 shared downregulated markers were observed between DEGs and DEPs. Among these 35 candidates from biomarker profiling, three upregulated markers were finally verified via data-independent acquisition (DIA) proteomic analysis using additional individual AH samples, namely metallopeptidase inhibitor 1 (TIMP1), Fc fragment of IgG binding protein (FCGBP), and angiopoietin-related protein 7 (ANGPTL7). Furthermore, we confirmed these AH biomarkers for CECD using individual immunoassay validation. Conclusively, our findings may provide valuable insights into the disease process and identify biofluid markers for the assessment of CEC function during BK development.

Long-Term Outcomes of Descemet Membrane Endothelial Keratoplasty: Effect of Surgical Indication and Disease Severity

PURPOSE

The aim of this study was to evaluate clinical outcomes and graft survival in a large patient cohort up to 10 years after Descemet membrane endothelial keratoplasty (DMEK) based on surgical indication and Fuchs endothelial corneal dystrophy (FECD) severity.

METHODS

The cohort in this retrospective study included 750 eyes that underwent DMEK for FECD (86%), bullous keratopathy (BK, 9%), and other indications (5%). Based on the modified Krachmer grading, 186 eyes (29%) had moderate FECD (Krachmer grade 3-4) and 440 eyes (68%) had advanced FECD (Krachmer grade 5-6). Main outcome measures were best-corrected visual acuity (BCVA), central corneal thickness, endothelial cell density (ECD), endothelial cell loss (ECL), postoperative complication rate, and graft survival.

RESULTS

The mean 10-year BCVA was 0.08 ± 0.28 logMAR (n = 96), and the BCVA remained stable between 5 and 10 years postoperatively (all P > 0.05). The mean ECL at 5 and 10 years was 56% ± 17% (n = 460) and 66% ± 14% (n = 96), respectively ( P < 0.05). The 10-year graft survival rate for the total cohort was 0.85 (95% confidence interval, 0.82-0.89). BCVA and ECD differed at 1 to 5 years between eyes with different surgical indications (all P < 0.05), and FECD eyes had higher graft survival compared with BK eyes (0.90 vs. 0.60, P = 0.001). Moderate FECD eyes had better BCVA, ECD, and graft survival outcomes than advanced FECD eyes (all P < 0.05). Minor graft detachment ( P = 0.04) and lower donor ECD ( P = 0.01) were related to lower 10-year ECD.

CONCLUSIONS

Long-term outcomes and graft survival after DMEK were better in FECD eyes than BK eyes and were also related to FECD disease severity. Eyes operated for moderate FECD showed the highest graft survival probability and excellent long-term outcomes.

Effect of Head Trauma-Related Deaths on Corneal Endothelial Cell Loss in Eye Bank Donors

PURPOSE

The purpose of this study was to examine the effect of head trauma-related deaths on corneal endothelial cell density (ECD) in eye bank donors.

METHODS

This is a retrospective study of 287 corneas from donors with causes of death secondary to motor vehicle accident with sustained head trauma (n = 50), gunshot wound to the head (n = 138), fall with sustained head trauma (n = 2), and non-head-related traumatic causes of death (n = 97). Donors older than age 50 years were excluded due to concern for undiagnosed Fuchs endothelial dystrophy as a potential confounder for the cause of endothelial cell loss. Donor characteristics, ECD, and focal endothelial cell loss on specular microscopy were compared between the groups. Donors in the head trauma and nonhead trauma groups were matched by age; there were 42 age-matched donors in both groups.

RESULTS

Age and ECD were negatively correlated (Pearson correlation coefficient = -0.57). Death-to-preservation time was not significantly different between the 2 groups ( P value = 0.59). The mean ECD in the head trauma group was 2859 ± 370 cells/mm 2 and 3041 ± 464 cells/mm 2 in the nonhead trauma group. The head trauma group had a lower ECD (178 ± 70 cells/mm 2 , P value = 0.013). After matching for age, the difference in ECD between the 2 groups was -94 ± 82 cells/mm 2 ( P value = 0.26). The adjusted odds of having focal endothelial cell loss was not statistically significant ( P value = 0.50) between the groups.

CONCLUSIONS

After statistical adjustments, there were no differences between the head trauma and nonhead trauma groups.

Preoperative surgeon evaluation of corneal endothelial status: the Viability Control of Human Endothelial Cells before Keratoplasty (V-CHECK) study protocol

INTRODUCTION

The success of keratoplasty strongly depends on the health status of the transplanted endothelial cells. Donor corneal tissues are routinely screened for endothelial damage before shipment; however, surgical teams have currently no means of assessing the overall viability of corneal endothelium immediately prior to transplantation. The aim of this study is to validate a preoperative method of evaluating the endothelial health of donor corneal tissues, to assess the proportion of tissues deemed suitable for transplantation by the surgeons and to prospectively record the clinical outcomes of a cohort of patients undergoing keratoplasty in relation to preoperatively defined endothelial viability.

METHODS AND ANALYSIS

In this multicentre cohort study, consecutive patients undergoing keratoplasty (perforating keratoplasty, Descemet stripping automated endothelial keratoplasty (DSAEK), ultra-thin DSAEK (UT-DSAEK) or Descemet membrane endothelial keratoplasty) will be enrolled and followed-up for 1 year. Before transplantation, the endothelial viability of the donor corneal tissue will be evaluated preoperatively through trypan blue staining and custom image analysis to estimate the overall percentage of trypan blue-positive areas (TBPAs), a proxy of endothelial damage. Functional and structural outcomes at the end of the follow-up will be correlated with preoperatively assessed TBPA values.

ETHICS AND DISSEMINATION

The protocol will be reviewed by the ethical committees of participating centres, with the sponsor centre issuing the final definitive approval. The results will be disseminated on ClinicalTrials.gov, at national and international conferences, by partner patient groups and in open access, peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT05847387.

Evaluation of corneal endothelium and correlation with disease severity in patients with Graves' ophthalmopathy: A specular microscopy-based study

PURPOSE

To investigate the possible corneal endothelial damage in Graves' ophthalmopathy (GO) and its relationship with GO activity.

METHODS

This cross-sectional study included 101 eyes of 55 patients with GO. Each eye was assigned a specific clinical activity score (CAS). Accordingly, they were classified as active (CAS ≥ 3) or inactive (CAS< 3). The corneal endothelium was measured using a non-contact specular microscope (Tomey EM-4000; Tomey Corp.). Endothelial cell density (ECD), average cell area (ACA), standard deviation of cell area (SD), coefficient of variation in cell area (CV), hexagonal cell ratio (HEX), and central corneal thickness (CCT) were recorded.

RESULTS

Among the eyes included in the study, 71 had inactive GO and 30 had active GO. ACA and HEX levels were lower (p<0,001) and CV values were higher (p<0.001) in patients with GO than in healthy subjects. Corneal endothelial cell morphology was altered in active GO compared to inactive GO. The SD (p=0,009) and CV (p<0,001) were significantly higher in active GO than in inactive GO. When the parameters examined were correlated with CAS, a statistically significant positive correlation was observed between proptosis (p=0,036, r=0,385) and CV (p=0,001, r=0,595).

CONCLUSION

Our study confirmed that morphological changes occur in the corneal endothelium of patients with GO. CV and SD values, in conjunction with CAS, can be used as non-invasive and quantitative indices to examine the activity status of GO. The demonstration of endothelial changes even in GO eyes with low CAS may be considered an incentive to include non-contact specular microscopy in the routine clinical evaluation of all patients with GO.

Long-term Outcomes After Lamellar Endothelial Keratoplasty Compared With Penetrating Keratoplasty for Corneal Endothelial Dysfunction: A Systematic Review

PURPOSE

The purpose of this study is to evaluate long-term outcomes of endothelial keratoplasty (EK) compared with penetrating keratoplasty (PK) for corneal endothelial dysfunction [Fuchs endothelial corneal dystrophy (FECD) and bullous keratopathy (BK)].

METHODS

In this systematic review, we searched PubMed, the Cochrane Library, and Embase up to May 2022 and considered all types of studies addressing our objective. Graft survival at 5, 10, and 15 years was the main outcome.

RESULTS

Fifty cohort studies were included. At 5 years, in FECD and BK, graft survival seemed higher after EK than PK. Two comparative studies showed either a higher 5-year graft survival after EK than PK or no significant differences. Including noncomparative studies, in FECD, the 5-year graft survival ranged from 0.69 to 0.98 for PK, from 0.93 to 1.00 for DSEK, and from 0.93 to 0.99 for Descemet membrane endothelial keratoplasty (DMEK). In BK, the 5-year graft survival ranged from 0.39 to 0.91 for PK, from 0.65 to 0.89 for DSEK, and from 0.84 to 0.95 for DMEK. The 10-year graft survival ranged from 0.20 to 0.90 for PK and from 0.62 to 0.92 for EK. The mean 5-year best spectacle-corrected visual acuity ranged from 0.73 to 0.43 LogMAR for PK, from 0.61 to 0.09 for DSEK, and from 0.31 to 0.05 for DMEK. The 5-year rejection rate ranged from 11.0% to 28.7% for PK, from 5.0% to 7.9% for DSEK, and from 1.7% to 2.6% for DMEK.

CONCLUSIONS

These results suggest a higher 5-year graft survival and better secondary outcomes after EK. Nevertheless, the level of evidence was low.

PROSPERO REGISTRATION

CRD42021260614.

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.

The Interplay between Metabolites and MicroRNAs in Aqueous Humor to Coordinate Corneal Endothelium Integrity

Purpose

The purpose of the study was to clarify the interplay between metabolites and microRNAs (miRs) in the aqueous humor (AqH) of bullous keratopathy (BK) patients to retain human corneal endothelium (HCE) integrity.

Design

Prospective, comparative, observational study.

Participants

A total of 55 patients with BK and 31 patients with cataract (Cat) as control.

Methods

A biostatic analysis of miRs and metabolites in the AqH, hierarchical clustering, and a least absolute shrinkage and selection operator (Lasso) analysis were employed. The miR levels in AqH of BK (n = 18) and Cat (n = 8) patients were determined using 3D-Gene human miR chips. Hierarchical clusters of metabolites detected by liquid chromatography-mass spectrometry or gas chromatography-mass spectrometry in AqH specimens from 2 disease groups, BK (total n = 55) and Cat (total n = 31), were analyzed twice to confirm the reproducibility. The analytical procedure applied for investigating the association between metabolites and miRs in AqH was the exploratory data analysis of biostatistics to avoid any kind of prejudice. This research procedure includes a heat-map, cluster analysis, feature extraction techniques by principal component analysis, and a regression analysis method by Lasso. The cellular and released miR levels were validated using reverse transcription polymerase chain reaction and mitochondria membrane potential was assessed to determine the functional features of the released miRs.

Main Outcome Measures

Identification of interacting metabolites and miRs in AqH attenuating HCE degeneration.

Results

The metabolites that decreased in the AqH of BK patients revealed that 3-hydroxyisobutyric acid (HIB), 2-aminobutyric acid (AB) and branched-chain amino acids, and serine were categorized into the same cluster by hierarchical clustering of metabolites. The positive association of HIB with miR-34a-5p was confirmed (P = 0.018), and the Lasso analysis identified the interplay between miR-34a-5p and HIB, between miR-24-3p and AB, and between miR-34c-5p and serine (P = 0.041, 0.027, and 0.009, respectively). 3-hydroxyisobutyric acid upregulated the cellular miR-34a expression, mitochondrial membrane potential, and release of miR-184 in dedifferentiated cultured HCE cells.

Conclusions

Metabolites and miRs in AqH may synchronize in ensuring the integrity of the HCE to maintain efficient dehydration from the stroma.

Financial Disclosures

Proprietary or commercial disclosure may be found after the references.

Role of Oxidative Stress in the Disruption of the Endothelial Apical Junctional Complex During Corneal Cold Storage

Purpose: To characterize the impact of corneal cold storage (CS) on the endothelial apical junctional complex (AJC). Methods: Porcine corneas were held in CS (4°C; 1-7 days) with Cornisol™ preservation medium supplemented with epothilone B (EpoB; microtubule stabilizer; 100 nM), SB-203580 (p38 mitogen-activated protein [MAP] kinase inhibitor; 20 μM), or antioxidants (quercetin, 100 μM; vitamin E, 1 mM; deferoxamine, an iron chelator, 10 mM). After CS termination, the damage to endothelial AJC was characterized by imaging perijunctional actomyosin ring (PAMR) and zonula occludens (ZO-1). The effects of EpoB and SB-203580 were characterized by imaging microtubules. The loss in the barrier function was assessed in cultured cells grown on biotin-coated gelatin by permeability to fluorescein isothiocyanate (FITC)-avidin. The accumulation of reactive oxygen species (ROS), altered mitochondrial membrane potential (MMP), lipid peroxidation, and lactate dehydrogenase (LDH) release were also determined in response to CS. Results: CS led to the loss of microtubules, destruction of PAMR, and breakdown of ZO-1 in the endothelium. The severity of damage increased when CS was prolonged. Although rewarming of the tissue increased the damage, the effect was marginal. CS also induced accumulation of ROS, alteration in MMP, lipid peroxidation, enhanced LDH release, and increased permeability to FITC-avidin. These changes were opposed by EpoB, SB-203580, and antioxidants. Conclusion: Corneal CS destroys AJC of the endothelium, leading to loss of its barrier function. The effects were surmounted by microtubule stabilization, p38 MAP kinase inhibition, and antioxidants. Thus, there is potential for reformulation of the preservation medium to maintain the health of the donor corneal endothelium before transplantation.

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

Purpose

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

Design

Prospective cohort study.

Participants

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

Methods

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

Main Outcome Measures

Endothelial cell density and ECL at 36 months postoperative.

Results

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

Conclusions

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

Financial Disclosures

Proprietary or commercial disclosure may be found after the references.

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.

Superiority of Mature Differentiated Cultured Human Corneal Endothelial Cell Injection Therapy for Corneal Endothelial Failure

PURPOSE

To investigate the safety and efficacy of cultured human corneal endothelial cell (hCEC) injection therapy with mature differentiated (mature) cell subpopulations (SPs) for corneal endothelial failure (CEF).

DESIGN

Comparative, interventional case series.

METHODS

This study involved 18 eyes with CEF that underwent cultured hCEC injection therapy, categorized into 2 groups: (1) 11 eyes administered a relatively lower proportion (0.1 to 76.3%) of mature cell SPs (group 1 [Gr1]), and (2) 7 eyes administered a relatively higher proportion (>90%) of mature cell SPs (group 2 [Gr2]). From 1 week to 3 years postoperation, corneal endothelial cell (CEC) density (CECD), central corneal thickness (CCT), and best-corrected visual acuity (BCVA) were recorded, and the CEC parameter's "spring constant" was calculated. The proportion of mature SPs was evaluated by fluorescence-activated cell sorting analysis based on cell-surface markers.

RESULTS

At 3 years postoperation, corneal restoration with improved BCVA was attained in 10 of the 11 Gr1 eyes and all Gr2 eyes, the median CECD in Gr2 (3083 cells/mm²; range, 2182-4417 cells/mm²) was higher than that in Gr1 (1349 cells/mm²; range, 746-2104 cells/mm²) (P < .001), and the spring constant verified the superiority of the mature cultured hCECs. From 24 weeks through 3 years postoperation, the median percentage of CECD decrease was 3.2% in Gr2 and 23.6% in Gr1 (P < .005). CCT recovery was prompt and constant in Gr2, while diverse in Gr1. No adverse events were observed.

CONCLUSION

Our findings showed that mature cell SPs for hCEC injection therapy provide rapid recovery of CCT, better CECD, and low CECD attrition over 3 years postsurgery.

Intracellular pH affects mitochondrial homeostasis in cultured human corneal endothelial cells prepared for cell injection therapy

This study aimed to uncover the mechanism responsible for the clinical efficacy of cell injection therapy with fully differentiated cultured cells. Analysis of polarized expression of ion transporters on cultured human corneal endothelial cells (CECs) subpopulations (SPs) was performed. The intracellular pH (pHi) between two CEC SPs, distinct in the proportion of differentiated cells, was measured, and the association with mitochondrial respiration homeostasis was investigated. The effects of the ion transporter inhibition by their selective inhibitors or siRNA transfection were also explored. Na⁺/K⁺-ATPase, Aquaporin 1, SLC4A11, NBCe1, NHE1 as transporters, and ZO-1, were all selectively expressed in differentiated SPs, but were almost null in the cell-state-transitioned SPs. We also confirmed that the pHi of CEC SPs affected their mitochondrial respiration by modulating the expression of these ion transporters via inhibitors or siRNA transfection. Ion and water transporters might participate in the maintenance of pHi and mitochondria homeostasis in differentiated SPs, which may contribute, combined with integral barrier functions, to efficient water efflux. The differences in intracellular pH between the two SPs is attributed to variations in the expression profile of specific ion transporters and mitochondrial functions, which may associate with the efficacy of the SPs in cell injection therapy.

Influence of graft vascularization on graft survival following homologous limbo-keratoplasty

PURPOSE

Limbo-keratoplasty enables visual improvement and limbal stem cell transplantation at the same. During follow-up, most grafts show vascularization of the limbus. However, it is unclear whether vascularization is harmful due to immunologic effects or helpful to nourish the limbal stem cells and is therefore necessary for a clear graft. The aim of our study is to analyze the influence of graft vascularization on graft survival following homologous limbo-keratoplasty.

METHODS

In this retrospective study, we assessed all consecutive limbo-keratoplasties performed in our hospital. All eyes with suitable photo-documentation were included and divided into two groups (limbal stem cell deficiency and corneal dystrophy). We categorized the grade of vascularization (0, 1, 2, 3, 3b) and analyzed clear graft survival, recurrence of the underlying disease and the endothelial cell density (ECD) with regard to the reason for the graft. Event rates were estimated with the Kaplan-Meier method.

RESULTS

A total of 79 eyes with limbal stem cell deficiency and 15 with corneal dystrophies were analyzed. A high degree of graft vascularization had a tendency for better graft survival in limbal stem cell deficiency, whereas in corneal dystrophies, grafts with no vascularization had preferable outcomes. Recurrence-free graft survival was only seen in grade 1 and 3 vascularization in corneal dystrophies.

CONCLUSION

Vascularization of the limbus seems to have an impact on the long-term outcome of limbo-keratoplasty. The effect seems to be favorable in limbal stem cell deficiency and on recurrence rates in corneal dystrophies. However, the latter might be overshadowed by an unfavorable immunologic effect in corneal dystrophies where the baseline immunologic risk profile is commonly more favorable than in limbal stem cell deficiency.

Repressed miR-34a Expression Dictates the Cell Fate to Corneal Endothelium Failure

Purpose

To reveal the mechanism triggering the functional disparity between degenerated and non-degenerated corneal endothelium cells in the water efflux from corneal stroma to the anterior chamber.

Methods

The varied levels of the microRNA (miR)-34, miR-378, and miR-146 family in human corneal endothelium and cultured cells thereof were investigated using 3D-Gene Human miRNA Oligo Chips. Concomitantly, CD44, p53, c-Myc, matrix metalloprotease (MMP)-2 expression, and Ras homolog gene family member A (Rho A) activity was correlated to the expression intensities of these microRNAs, partly complemented with their altered expression levels with the transfection of the corresponding mimics and inhibitors. The levels of miRs were further associated with intracellular pH (pHi) and mitochondrial energy homeostasis.

Results

P53-inducible miR-34a/b repressed CD44 expression, and CD44 was repressed with the elevated c-Myc. The repressed miR-34a activated the CD44 downstream factors Rho A and MMP-2. MiR-34a mimics downregulated pHi, inducing the skewing of mitochondrial respiration to oxidative phosphorylation. The oxidative stress (H₂O₂) induced on human corneal endothelial cells, which repressed miR-34a/b expression, may account for the impaired signaling cascade to mitochondrial metabolic homeostasis necessary for an efficient water efflux from the corneal stroma.

Conclusions

The upregulated expression of CD44, through repressed miR-34a/b by reactive oxygen species and elevated c-Myc by oxidative stress, may impair mitochondrial metabolic homeostasis, leading to human corneal endothelial failure.

Long-Term Outcomes of Two-Piece Mushroom Keratoplasty for Traumatic Corneal Scars

PURPOSE

To report the outcomes of 2-piece microkeratome-assisted mushroom keratoplasty (MK) for eyes with full-thickness traumatic corneal scars and otherwise functional endothelium following corneal penetrating injury.

DESIGN

This was an interventional case series.

METHODS

In this single-center study, 41 consecutive eyes with traumatic corneal scars that underwent 2-piece microkeratome-assisted mushroom keratoplasty were evaluated. The 2-piece mushroom graft consisted of an anterior lamella 9 mm in diameter and a posterior lamella 6 mm in diameter. Outcome measures were best spectacle-corrected visual acuity (BSCVA), refractive astigmatism (RA), endothelial cell density, and postoperative complication rates.

RESULTS

Of the 41 total cases, 38 eyes (93%) reached Snellen vision ≥20/100, 36 (88%) reached ≥20/60, 29 (71%) reached ≥20/40, and 13 (32%) reached ≥20/25 2 years following MK. Excluding eyes with vision-impairing comorbidities, baseline logMAR BSCVA (1.41 ± 0.73) significantly improved annually during the first 2 years (P < 0.001), reaching 0.16 ± 0.13 at year 2, which subsequently remained stable up to 10 years (P = .626). The RA exceeded 4.5 diopters in 2 cases (5%) after wound revision for high-degree astigmatism in 5 cases. Endothelial cell loss was 35.1% at 1 year, with an annual decline of 2.9% over 10 years. Elevation in IOP was observed postoperatively in 7 eyes, of which 6 had pre-existing glaucoma. The 10-year cumulative risk for graft rejection and failure was 8.5% and 10%, respectively.

CONCLUSION

Two-piece microkeratome-assisted MK for traumatic corneal scars can allow excellent visual rehabilitation with relatively stable ECL and low rates of immunologic rejection and graft failure.

Management of Late Descemet's Membrane Detachment After Penetrating Keratoplasty in Keratoconus

PURPOSE

The purpose of this study was to describe the feasibility of Descemet membrane endothelial keratoplasty (DMEK) as a treatment modality for spontaneous detachment of DM (DMD) decades after penetrating keratoplasty (PK) for keratoconus.

METHODS

We describe the clinical characteristics and therapeutic surgical approach in 6 eyes of 5 patients with DMD. Clinical images, anterior segment optical coherence tomography scans, and histological findings are presented.

RESULTS

Mean age of patients at time of diagnosis was 60 years (range 56-66 years). Mean interval between PK and occurrence of DM detachment was 36 years (range 29-45 years). In 4 of 6 eyes, air injections into the anterior chamber were initially attempted to reattach DM to the stroma but without long-lasting effect. Two eyes underwent repeat PK because of pronounced ectasia after long-standing DMD and stromal scars. DMEK was performed successfully in 4 eyes leading to an increase in visual acuity and a reduction in central corneal thickness. Electron microscopy showed abnormal vacuolar inclusions and collagenous material in the posterior nonbanded layer and a separation of the anterior banded layer from the posterior nonbanded layer.

CONCLUSIONS

This case series provides evidence that DMEK is a viable option in eyes with spontaneous DM detachment after PK. Visual outcome is limited by the persisting high astigmatism in the ectatic cornea. Illustrated by a small series of patients, the results of DMEK in this condition are presented and new findings about the pathophysiology are given.

Clinical Outcomes in Maximum Tolerated Medical Therapy in Penetrating Keratoplasty for Bullous Keratopathy

Purpose

To compare the clinical outcomes of maximum tolerated medical therapy (MTMT) in patients with penetrating keratoplasty (PKP) with those of Ahmed glaucoma valve (AGV) implantation.

Methods

The medical records were retrospectively reviewed in patients who had undergone PKP for bullous keratopathy and were treated with MTMT or AGV implantation for the management of glaucoma. A total of 18 bullous keratopathic patients were investigated between January 2010 and February 2017: 9 patients treated with MTMT and 9 patients treated with AGV implantation. Non-corrected visual acuity (NCVA), intraocular pressure (IOP), endothelial cell density (ECD), hexagonality, coefficient of variation (CV), central corneal thickness (CCT), median survival time of the graft, and the presence of epithelial keratopathy were compared between the groups at each time point or between baseline and after treatment of glaucoma in each group.

Results

There were no significant differences in the visual acuity and corneal thickness between the two groups or within each group over time. Both groups showed a significant reduction in IOP compared with the baseline IOP, and IOP reductions were greater in the AGV group than in the MTMT group (p = 0.040). Significant ECD reductions were found in each group between the baseline and 6 months (p = 0.008 in the MTMT group, p = 0.015 in the AGV group); however, no differences were found between the two groups until 12 months. The significant hexagonality reduction was found in the AGV group between the baseline and 12 months (p = 0.018). The median survival time showed no significant difference in the survival analysis.

Conclusions

Maximum tolerated medical therapy in penetrating keratoplasty for bullous keratopathy seems to similarly affect the endothelial cell density or graft survival when compared with at least 12 month-followed Ahmed glaucoma valve implantation.

The Cologne-Mecklenburg-Vorpommern DMEK Donor Study (COMEDOS) - design and review of the influence of donor characteristics on Descemet membrane endothelial keratoplasty (DMEK) outcome

Background

Posterior lamellar keratoplasty and especially Descemet membrane endothelial keratoplasty (DMEK) are gaining interest worldwide. Little is known about the influence of donor factors on DMEK outcome. Here we provide an overview of the existing peer-reviewed literature on this topic and present the design of the upcoming cooperation study COMEDOS (Cologne-Mecklenburg-Vorpommern DMEK Donor Study).

Methods

A literature search of PubMed and MEDLINE was conducted to retrieve articles published between September 2013 and May 2021. Seventeen peer-reviewed articles were selected. Design and concept of the prospective COMEDOS are outlined.

Results

Main interest parameters were the donor diabetes mellitus status, age, and lens status. There is a large heterogeneity regarding the sample size, study design, and investigated parameters. There seems to be a consensus that younger donors are associated with tighter rolls, a more difficult preparation, and unfolding setting. Diabetic donors seem to increase the risk of tissue tearing due to adherences and result more frequently in preparation failure. The COMEDOS aims not only to analyze the diabetes status of the donor, but also to correlate all donor systemic comorbidities and their ophthalmologic history to the DMEK clinical outcome. Furthermore, a correlation of Descemet membrane lamella preparation and surgery outcome is planned.

Conclusion

Currently, there is a lack of knowledge regarding the effect and impact of donor tissue characteristics on DMEK outcome and complications. An in-depth investigation is planned by the upcoming COMEDOS to close this knowledge gap.

Association between aqueous humor cytokines and postoperative corneal endothelial cell loss after Descemet stripping automated endothelial keratoplasty

This study measured the intraoperative anterior aqueous humor concentrations of various cytokines during corneal endothelial transplantation and searched for relationships between these concentrations and postoperative corneal endothelial cell (CEC) depletion. We recruited 30 consecutive patients who underwent corneal endothelial transplantation with Descemet’s stripping automated endothelial keratoplasty (DSAEK) at Tohoku University Hospital between February 2014 and July 2017. During surgery, we obtained aqueous humor samples and later measured the concentrations of 27 cytokines with a Multiplex Bead Assay (Bio-Plex Pro). We counted CECs 1, 6 and 12 months after surgery, and used Spearman’s rank correlation coefficient to identify relationships between CEC depletion and the concentrations of detected cytokines. The loss of CECs 1–6 months after surgery was significantly correlated with IL-7, IP-10, MIP-1a and MIP-1b concentrations (-0.67, -0.48, -0.39, and -0.45, respectively, all P <0.01). CEC loss 1–12 months after surgery was significantly correlated with IL-1b, IL-7, IP-10 and RANTES concentrations (-0.46, -0.52, -0.48, and -0.43, respectively). Multiple regression analysis showed that IL-7 concentration was significantly associated with CEC loss 1–6 months after surgery (b = -0.65, P < 0.01) and IP-10 concentration was associated with CEC loss 1–12 months after surgery (β = -0.38, P < 0.05). These results suggest that not only inflammatory cytokines but also IL-7, a cytokine related to lymphocytes, may be involved in the depletion of CECs after DSAEK, particularly depletion that occurs relatively early.

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.

Corneal Endothelium: A Promising Quantitative Index for Graves Ophthalmopathy Activity Evaluation

PURPOSE

To investigate the corneal endothelium damage in Graves ophthalmopathy (GO) and its role as a promising quantitative index to evaluate GO activity.

DESIGN

Cross-sectional study.

METHODS

This study included 128 eyes of 64 patients with GO. All subjects underwent ophthalmologic examinations, including proptosis, tear break-up time (BUT), corneal fluorescein staining, and Schirmer test. Corneal endothelium was measured by noncontact specular microscope and ocular biometric parameters were measured by IOLMaster 700. Each eye was assigned a specific clinical activity score (CAS), then grouped as active (CAS ≥3 points) or inactive (CAS <3 points). Ocular parameters between the 2 groups were compared using generalized estimating equations accounting for inter-eye correlation, and receiver operating characteristic (ROC) curves were also obtained. Main outcome measures were parameters of corneal endothelium.

RESULTS

Among the included eyes, 81 eyes had inactive GO and 47 eyes had active GO. Corneal endothelial cell morphology was altered in active GO compared with inactive GO. The coefficient variation of cell area (CV) was significantly higher in active GO compared with inactive GO (37.0 [34.4-41.2]% vs 33.9 [30.9-36.8]%, P = .001), and positively correlated with CAS (r = 0.322, P < .001). Moreover, CV showed a diagnostic capacity to differentiate the active eyes from inactive eyes. The area under the ROC curve was 0.705.

CONCLUSIONS

Active GO had morphologic changes in corneal endothelium compared with inactive GO. CV is a sensitive indicator to reflect corneal endothelial function, and has the potential to be adopted as a noninvasive, objective, and quantitative index for evaluating the activity status of GO patients.

Evaluation of various preservation media for storage of donor corneas

Purpose

To compare the physical and microbiological characteristics of McCarey-Kaufman (MK), Cornisol, and Optisol-GS media and evaluate the outcomes of keratoplasty performed using corneas stored in these three media.

Methods

The study involved 60 donor corneas which were distributed in 3 groups: MK, Cornisol, and Optisol-GS. Corneas in these groups were further analyzed based on the type of keratoplasty performed (full thickness versus endothelial keratoplasty). At baseline, the endothelial cell density and death to preservation time of donor corneas were recorded. Following keratoplasty, patients were evaluated on day 1, at 1 month, 3 months, and 6 months follow-up. Outcomes were assessed in terms of corrected distance visual acuity (CDVA), endothelial cell density, percentage endothelial cell loss, and corneal thickness. The storage media were also assessed for their physical quality and their microbiological characteristics.

Results

Physical characteristics of all three media were found to be within normal limits. Mean CDVA was comparable among the 3 groups at 6-month follow-up. The absolute endothelial cell count values were significantly lower for corneas stored in MK medium (1873.7 ± 261.1 cells/mm²) compared to the Cornisol (2085.0 ± 230.3 cells/mm²) and Optisol-GS media [(2180.3 ± 217.2 cells/mm²) (P = <0.001)]. Corneas stored in Optisol-GS medium were significantly thinner at 1-month follow-up with no significant difference at 6 months (P = 0.66).

Conclusion

Optisol-GS and Cornisol media were found to preserve endothelial cell density better and stabilize corneal thickness earlier as compared to the MK medium. However, the functional outcomes were comparable among the three groups.

Long-Term Maintenance of Corneal Endothelial Cell Density After Corneal Transplantation

PURPOSE

To investigate the key factors associated with eyes with an endothelial cell density (ECD) of ≥2000 cells/mm at 5 years after corneal transplantation.

METHODS

This retrospective cohort study included 174 eyes that underwent penetrating keratoplasty by 1 corneal specialist surgeon at the Baptist Eye Institute, Kyoto, Japan, from 1998 through 2011 and that were carefully followed for over 5 years postoperative. In all operated eyes, corneal ECD was measured at 1, 2, 3, 4, and 5 years postoperative. Multivariate analysis with adjustment for preoperative donor ECD was performed between eyes with an ECD of ≥2000 cells/mm and those with an ECD of <2000 cells/mm at 5 years postoperative.

RESULTS

Of the 174 eligible eyes, 16 eyes (9.2%) had an ECD of ≥2000 cells/mm at 5 years postoperative, and the annual rate of endothelial cell loss (mean ± SD) was 2.3% ± 3.7%. Multivariate analysis findings revealed that the donor-associated and surgery-related factors were not significant factors. Only the recipient diagnosis of bullous keratopathy was significantly associated with an ECD of <2000 cells/mm at 5 years postoperative. Of those 16 eyes, 6 (37.5%) had a recipient diagnosis of bullous keratopathy.

CONCLUSIONS

None of the donor- and surgery-related factors, previously recognized as associated with a lower endothelial cell loss after penetrating keratoplasty, were found to be significant in this study, thus suggesting that there are still unknown factors associated with maintaining a higher ECD over the long-term postoperative period.

Effect of Donor Age on Graft Survival in Primary Penetrating Keratoplasty with Imported Donor Corneas

Purpose

To investigate the influence of donor age on corneal graft survival following primary penetrating keratoplasty (PK) with imported donor corneas.

Methods

The eyes of patients who underwent primary PK with imported donor corneas were classified retrospectively into two groups according to a donor-age cutoff of 65 years. Primary outcome measures were rejection-free graft survival and graft survival. Cox proportional hazard regression analysis was used to assess the factors affecting graft survival. Survival analysis was performed using the Kaplan-Meier method, while differences between groups were examined using a log-rank test. A subgroup analysis of low- and high-risk eyes according to preoperative diagnosis was also performed.

Results

A total of 140 eyes from 138 patients (age, 58 ± 18 years) were enrolled. Cox regression analysis revealed that the donor age of 65 years or older group presented an increased risk of both graft rejection and failure. Survival analysis revealed that rejection-free graft survival and graft survival rates were higher in eyes in the donor age of less than 65 years group. Finally, in the subgroup analysis, both rejection-free graft survival and graft survival rates were significantly higher in the donor age of less than 65 years group than in the donor age of 65 years or older group, but only in the low-risk subgroup.

Conclusions

Donor age may correlate with graft survival in primary PK performed with imported donor corneas. Donor age could be a considerable factor in primary PK with imported donor corneas, especially in preoperatively low-risk patients.

Impact of Pre- and Intraoperative Factors on Endothelial Cell Density in the Early and Late Stage after Penetrating Keratoplasty

AIM

This retrospective investigated the impact of donor age, recipient age, donor endothelial cell density, vis-à-tergo, and additional intraoperative lens exchange (triple-procedure) on overall early and late phase postoperative endothelial cell density (ECD) following penetrating keratoplasty (PKP) in various diagnosis groups.

PATIENTS AND METHODS

In 590 cases with diagnosed keratoconus (KC), Fuchs dystrophy (FD) and herpes simplex virus infection (HSV) who underwent PKP or triple surgery, the ECD in cells/mm² was analysed, both preoperatively, with all-sutures-in (early postoperative stage), and after last suture removal. The factors were tested by Mann-Whitney U-test, correlation analysis and linear regression analysis.

OUTCOME

Correlation analysis demonstrated a weak negative correlation between the patient's ECD and donor age (early postoperative stage: r = - 0.25, p < 0.001; after last suture removal: r = - 0.16; p = 0.003). Regression analysis revealed that donor age did not impact postoperative patient ECD. There was a weak negative correlation between postoperative ECD and recipient age (early postoperative stage: r = - 0.31, p < 0.001; after last suture removal: r = - 0.34, p < 0.001). Regression analysis confirmed the negative impact of recipient age on patient ECD (early postoperative stage: β = - 13.2, p = 0.001; after last suture removal: β = - 4.6, p < 0.001). Correlation analysis determined a weak positive correlation between postoperative ECD and donor endothelial cell density (early postoperative stage: r = 0.37, p < 0.001; after last suture removal: r = 0.32, p < 0.001). Regression analysis also determined that donor endothelial cell density had a positive impact on postoperative ECD following last suture removal (β = 0.4, p < 0.001). Vis-à-tergo and additional lens exchange (triple procedure) had no significant effect on postoperative ECD (p > 0.05). This was also confirmed by the results of the regression analysis after last suture removal.

CONCLUSION

Recipient age and donor endothelial cell density have a significant impact on postoperative ECD following PKP. Not all of the statistical tests proved donor age to be a significant influencing factor. Vis-à-tergo and additional lens exchange (triple procedure) had no significant effect on postoperative ECD following PKP.

Comparative Study of Long-term Graft Survival Between Penetrating Keratoplasty and Deep Anterior Lamellar Keratoplasty

PURPOSE

Endothelial failure and immunological graft rejection remain long-term complications leading to late graft failure in penetrating keratoplasty (PK). Deep anterior lamellar keratoplasty (DALK) has emerged as a viable alternative that enables preservation of the host's endothelial cells to eliminate risks of endothelial rejection and failure. The aim of this study was to compare long-term graft survival between PK and DALK.

DESIGN

Retrospective clinical cohort study.

METHODS

All consecutive primary grafts of DALKs (n = 362) and PKs (n = 307) performed for optical indications in a tertiary eye center from the ongoing, prospective Singapore Corneal Transplant Study. Ten-year graft survival outcomes were compared. Cases in which endothelial pathologies were diagnosed were excluded, as DALK was not performed for such cases. Main outcome measurements were mean graft survival rate.

RESULTS

The survival rate for PK was 94.4%, 80.4%, and 72.0% at 1, 5, and 10 years, respectively; and 95.8%, 93.9%, and 93.9% at 1, 5, and 10 years, respectively, for DALK (P = .001). Patients who underwent PK developed more complications of glaucoma (29.3% vs. 11.6%, respectively; P < .001), allograft rejection (16.6% vs. 1.7%, respectively; P < .001), epithelial problems (10.4% vs. 5.5%, respectively; P = .018), and nonimmunological failure (7.8% vs. 1.9%, respectively; P < .001), compared to DALK. Rates of graft failure attributable to rejection (36.7% vs. 5.9%, respectively; P = .015) and endothelial failure (36.7% vs. 5.9%, respectively; P = .015) were lower in DALK.

CONCLUSIONS

The 10-year graft survival for primary DALK was superior to that for PK for corneal pathologies with functional endothelium. Primary DALK resulted in fewer post-operative complications and lower rates of graft rejection and failure. This study strengthens the case in favor of performing DALK over PK when possible.

CLEAR - Scleral lenses

Scleral lenses were the first type of contact lens, developed in the late nineteenth century to restore vision and protect the ocular surface. With the advent of rigid corneal lenses in the middle of the twentieth century and soft lenses in the 1970's, the use of scleral lenses diminished; in recent times there has been a resurgence in their use driven by advances in manufacturing and ocular imaging technology. Scleral lenses are often the only viable form of contact lens wear across a range of clinical indications and can potentially delay the need for corneal surgery. This report provides a brief historical review of scleral lenses and a detailed account of contemporary scleral lens practice including common indications and recommended terminology. Recent research on ocular surface shape is presented, in addition to a comprehensive account of modern scleral lens fitting and on-eye evaluation. A range of optical and physiological challenges associated with scleral lenses are presented, including options for the clinical management of a range of ocular conditions. Future applications which take advantage of the stability of scleral lenses are also discussed. In summary, this report presents evidence-based recommendations to optimise patient outcomes in modern scleral lens practice.

Corneal endothelial status in different grades of late spontaneous in-the-bag IOL dislocation

PURPOSE

 To evaluate corneal endothelial cell density (ECD) in the eyes with different grades of late spontaneous in-the-bag intraocular lens (IOL) dislocation.

METHODS

 A prospective study included seventy-eight patients who applied for IOL dislocation. Overall 80 eyes were divided into four grades based on the in-the-bag IOL dislocation classification. All eyes underwent a complete ophthalmological examination. ECD was evaluated using in vivo corneal confocal microscopy.

RESULTS

 Median corneal ECD was 1929 (1022-2958) cells/mm2 of all the patients. The lowest number of ECD was in grade 2 (grade 1 median ECD 1990.33 (1182-2425.33) cells/mm2, grade 2-1577.0 (1022-2958) cells/mm2, grade 3-2205.84 (1259-2807.67) cells/mm2 and grade 4-2072.17 (1045-2581.0) cells/mm2). A statistically significant difference was observed between the median of ECD of grade 2nd and 3rd (p = 0.023). By grouping cases into those with and without glaucoma, we found that corneal ECD was significantly lower in eyes with glaucoma compared with eyes without glaucoma in grades 3 and 4 (p < 0.05), while in other grades, the difference did not reach the significance level. We divided the corneal ECD of all eyes into two categories ≤ 1500 cells/mm2 and  > 1500 cells/mm2. Logistic regression demonstrated that the odds of having corneal ECD less than 1500 cells/mm2 increased by 3.5-fold if patients with IOL dislocation had been diagnosed with glaucoma previously.

CONCLUSION

 Late spontaneous in-the-bag IOL dislocation reduced corneal ECD. Previously diagnosed glaucoma was the most common comorbidity. This condition has a significant impact on corneal ECD for patients with IOL dislocation.

Acute corneal edema decades after penetrating keratoplasty for keratoconus in eyes wearing scleral contact lenses

PURPOSE

To report three cases of acute corneal edema occurring decades after penetrating keratoplasty (PK) for keratoconus in eyes wearing scleral contact lenses (ScCLs) with previously clear corneal grafts.

METHODS

Retrospective chart review of three ScCL wearers presenting for sudden onset pain and blurred vision. Data extracted included clinical presentation, year and reason for PK, ocular medications and comorbidities, contact lens wearing history, results of any ancillary testing available including corneal topography, anterior segment optical coherence tomography (OCT), and specular microscopy surrounding the event, treatment and outcomes of intervention. The number of PK eyes fit with ScCLs in the author's practice was determined to estimate the prevalence of this event.

RESULTS

The three patients each had a longstanding PK for keratoconus performed between 33-35 years prior to presentation and recurrent ectasia. Each patient presented with an acute, painful eye and reduced vision either 3 days, 4 months or 9 years after refitting into ScCLs. Each eye had well demarcated focal microcystic epithelial and stromal edema within the graft and crossing the wound margin onto the host cornea. Although a definitive break or detachment of Descemet's membrane was not visualized, the presentations suggest these were episodes of acute hydrops.

CONCLUSIONS

Longstanding PKs with recurrent ectasia and acute focal edema suggestive of corneal hydrops is demonstrated in this case series of ScCL wearers. Although similar events have occurred as part of the natural history of post-PK corneas for keratoconus, the proximity of ScCL refitting to two of the events suggests some association.

Factors influencing endothelial cell density of corneas for transplantation

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

Long-Term Visual Outcomes and Clinical Course of Patients With Peters Anomaly

PURPOSE

To present long-term clinical and visual outcomes of patients with Peters anomaly.

METHODS

The charts of all patients diagnosed with Peters anomaly from January 2000 to December 2012 were reviewed retrospectively. Peters anomaly was classified as type I (with no lens involvement) or type II (presence of keratolenticular adhesions or cataract), with further severity grading to mild, moderate, and severe disease depending on corneal opacity location and size. Mild cases were observed. Moderate cases were managed with pupillary dilation either pharmacologically or surgically. Penetrating keratoplasty (PKP) was reserved for more severe opacity. The main outcome measures were final best spectacle-corrected visual acuity (BSCVA), incidence of glaucoma, graft survival, and nystagmus rates.

RESULTS

Sixty eyes of 40 patients were included in the study. The median age of patients at presentation was 0.5 ± 20.7 months (range, 0.0-111.0 months), with a mean follow-up time of 75.8 ± 52.9 months (range, 12.1-225.3 months). Overall, final best spectacle-corrected visual acuity ranged from 0.1 logMAR to no light perception with 33 eyes (55.9%) achieving vision of 1.0 logMAR or better. Clear grafts at the last follow-up were obtained in 67.6% (25/37) of transplanted eyes, 76.0% (19/25) in Peters type I, and 50.0% (6/12) in Peters type II (P = 0.11). The probability of a clear graft at 10 years was 74.2% and 38.9% for type I and type II, respectively. Glaucoma was diagnosed in 33.3% eyes, 90.0% of which occurred after PKP. Nystagmus was highly associated with PKP intervention, occurring in 81.1% (30/37) of eyes undergoing PKP compared with 34.8% (8/23) of eyes with no PKP (P = 0.0003).

CONCLUSIONS

Visual rehabilitation in Peters anomaly remains a challenge, but outcomes can be optimized using a comprehensive clinical management algorithm according to disease severity.

Gender medicine in corneal transplantation: influence of sex mismatch on rejection episodes and graft survival in a prospective cohort of patients

To evaluate the effect of donor-to-recipient sex mismatched (male donor corneas to female recipients) on the incidence of rejection episodes and failures up to 1 year after corneal transplantation. Prospective observational cohort study, with donor corneas randomly assigned and surgeons blind to the sex of donor. A unique eye bank retrieved and selected the donor corneas transplanted in 4 ophthalmic units in patients with clinical indication for primary or repeated keratoplasty for optical reasons, perforating or lamellar, either anterior or posterior. Rejection episode defined as any reversible or irreversible endothelial, epithelial or stromal sign, with or without development of corneal edema, and graft failure as a permanently cloudy graft or a regraft for any reason detected or acknowledged during a postoperative ophthalmic visit at any time up to 1 year after surgery were recorded.156 (28.6%) patients resulted donor-to-recipient gender mismatched for H-Y antigen (male donor to female recipient). During the 12 months follow-up, 83 (14.7%, 95% CI 12.0-17.9) grafts showed at least 1 rejection episode and 17 (3.2%, 95% CI 2.0-5.0) failed after immune rejection, among 54 (9.6%, 95% CI 7.4-12.3) grafts failed for all causes. No significant differences between matched and mismatched patients were found for cumulative incidence of both rejection episodes (15.2% and 13.5%) and graft failures following rejection (3.2% and 2.6%), respectively. Multivariable analyses showed that H-Y matching either is not a predictive factor for rejection or graft failure nor seems to influence incidence of failures on respect to patient's risk category. The lack of influence of donor-to-recipient mismatched on the rate of rejections and graft failures resulting from this study do not support the adoption of donor-recipient matching in the allocation of corneas for transplantation.

Five-Year Follow-up of First 11 Patients Undergoing Injection of Cultured Corneal Endothelial Cells for Corneal Endothelial Failure

PURPOSE

To report the safety and efficacy of a novel cell injection therapy using cultured human corneal endothelial cells (hCECs) for endothelial failure conditions via the report of the long-term 5-year postoperative clinical data from a first-in-humans clinical trial group.

DESIGN

Prospective observational study.

PARTICIPANTS

This study involved 11 eyes of 11 patients with pseudophakic endothelial failure conditions who underwent hCEC injection therapy between December 2013 and December 2014.

METHODS

All patients underwent follow-up examinations at 1 week, 4 weeks, 12 weeks, and 24 weeks and 1 year, 2 years, 3 years, 4 years, and 5 years after surgery. Specific corneal endothelial cell parameters (i.e., corneal endothelial cell density [ECD], coefficient of variation of area, and percentage of hexagonal cells) and central corneal thickness, best-corrected visual acuity (BCVA) on a Landolt C eye chart, and intraocular pressure (IOP) were recorded.

MAIN OUTCOME MEASURES

The primary outcome was the change in central ECD after cell injection therapy, and the secondary outcome was corneal thickness, BCVA, and IOP during the 5-year-postoperative follow-up period.

RESULTS

At 5 years after surgery, normal corneal endothelial function was restored in 10 of the 11 eyes, the mean ± standard deviation central corneal ECD was 1257 ± 467 cells/mm² (range, 601-2067 cells/mm²), BCVA improved significantly in 10 treated eyes, the mean visual acuity changed from 0.876 logarithm of the minimum angle of resolution before surgery to 0.046 logarithm of the minimum angle of resolution after surgery, and no major adverse reactions directly related to the hCEC injection therapy were observed.

CONCLUSIONS

The findings in this study confirmed the safety and efficacy of cultured hCEC injection therapy for up to 5 years after surgery.

Initial High-Dose Prophylaxis and Extended Taper for Mushroom Keratoplasty in Vascularized Herpetic Scars

PURPOSE

To report the outcomes of initial high-dose and extended taper of antiviral and steroid prophylaxis for the treatment of eyes with high-risk vascularized herpetic corneal scars that underwent 2-piece mushroom keratoplasty (MK).

DESIGN

Prospective interventional case series.

METHODS

In this single-center study, 52 consecutive eyes with vascularized (≥2 quadrants) herpetic corneal scars underwent 2-piece microkeratome-assisted MK. Initial high-dose and extended taper of combined oral and topical antiviral and steroid prophylaxis was administered. Outcome measures were best spectacle-corrected visual acuity (BSCVA), refractive astigmatism (RA), endothelial cell density, immunologic rejection, herpetic recurrence, and graft failure rates.

RESULTS

Excluding patients with vision-impairing comorbidities, baseline BSCVA (1.73 ± 0.67 logMAR) significantly improved annually during the first 2 years (P < .001, P = .016), reaching 0.17 ± 0.18 logMAR at year 2, and remaining stable up to 10 years (P = .662). At 2 years, 86% of eyes saw ≥20/40, 55% saw ≥20/25, and 18% saw ≥20/20 Snellen BSCVA. RA exceeded 4.5 diopters in 7% of cases after wound revision for high-degree astigmatism in 7 cases. Endothelial cell loss was 40.9% at 1 year with an annual decline of 3.1% over 10 years. The 10-year cumulative risk for immunologic rejection, herpetic recurrence, and graft failure was 9.7%, 7.8%, and 7.6%, respectively.

CONCLUSIONS

Initial high dose and extended taper of antiviral and steroid prophylaxis for MK in high-risk, vascularized herpetic corneal scars achieves clinical outcomes that remain stable for up to 10 years after surgery with minimal risk of immunologic rejection, herpetic recurrence and graft failure.

Descemet Membrane Endothelial Keratoplasty: Ten-Year Graft Survival and Clinical Outcomes

PURPOSE

To evaluate the 10-year graft survival and clinical outcomes of the first case series after Descemet membrane endothelial keratoplasty (DMEK).

DESIGN

Retrospective, interventional case series.

METHODS

After excluding the very first 25 DMEK eyes that constitute the technique learning curve, the following 100 consecutive primary DMEK eyes (88 patients) were included. Main outcome parameters (survival, best-corrected visual acuity [BCVA], central endothelial cell density [ECD], and central corneal thickness [CCT]) were evaluated up to 10 years postoperatively, and postoperative complications were documented.

RESULTS

At 5 and 10 years after DMEK, 68 and 57 of 100 eyes, respectively, were still available for analysis. Of those eyes, 82% and 89% reached a BCVA of ≥20/25 (decimal VA ≥0.8) at 5- and 10 years postoperatively, respectively. Preoperative donor ECD decreased by 59% at 5 years and 68% at 10 years postoperatively. CCT averaged 668 ±74 μm preoperatively and 540 ± 33 μm and 553 ± 43 μm at 5 and 10 years, respectively, after surgery. Within 10 years, 4% of eyes developed allograft rejection, no primary graft failures occurred, and 6% of the eyes developed secondary graft failure. Graft survival probability was 0.83 (95% confidence interval [CI], 0.75-0.92) and 0.79 (95% CI, 0.70-0.88) at 5 and 10 years postoperatively, respectively.

CONCLUSIONS

Most eyes that underwent surgery in the pioneering phase of DMEK showed excellent and stable clinical outcomes with low postoperative complication rates and promising graft longevity over the first decade after surgery. This suggests that DMEK may be a safe long-term treatment option for corneal endothelial diseases.

Proliferation of Human Corneal Endothelia in Organ Culture Stimulated by Wounding and the Engineered Human Fibroblast Growth Factor 1 Derivative TTHX1114

Purpose: Corneal endothelial dystrophies are characterized by endothelial cell loss and dysfunction. Recent evidence suggests that corneal endothelial cells (CECs) can regenerate although they do not do so under normal conditions. This work sought to test whether CECs can be stimulated to proliferate in organ culture by wounding and/or by treatment with the engineered human fibroblast growth factor 1 (FGF1) derivative TTHX1114.

Methods: Human donor corneas obtained from eye banks were maintained in organ culture in the presence or absence of TTHX1114. Wounds in the corneas were created by quartering the corneas. The CEC monolayer was identified as a regular layer by Hoechst staining of the nuclear DNA with cell outlines delineated by immunohistochemical identification of ZO-1. Nuclei and nuclei incorporating 5-ethynyl-2′-deoxyuridine (EdU) were counted using ImageJ.

Results: CECs in normal corneas in undisturbed monolayers had low, but measurable, rates of proliferation. CECs at the edge of a wound had higher rates of proliferation, probably due to the release of contact inhibition. TTHX1114 increased proliferation at wound edges. After 7 days of culture, proliferating CECs formed contiguous groups of labeled cells that did not migrate away from one another. TTHX1114-treated cells, including the EdU labeled proliferating cells, retained normal morphology, including cell/cell junction ZO-1 staining.

Conclusions: Proliferation of CECs in organ-cultured corneas is low, but can be stimulated by wounding or by the administration of TTHX1114 with the effects of each being additive. The CEC monolayer appears to have a population of progenitor cells that are susceptible to stimulation.

The Causes for the Loss of Cellular Material at the Qualification Stage and the Influence of the Patient's Flora on Culture Infection

There are several causes leading to the loss of cellular material earmarked for transplantation. This paper aims to evaluate the number of lost donors and lost cells in the culture by means of verifying both the results of the qualification tests and the presence of microorganisms in the cellular material. The analysis involved 86 donors hospitalized for thermal burns, from whom cells were harvested for keratinocyte and fibroblast cultures in the years 2011 to 2015. All potential donors underwent qualification tests: Anti-HIV-1,2; HBsAg; Anti-HCV-Ab; HBc, and a specific test for syphilis. In the case of skin fragments collected for culturing, the microbiological tests included the carrying fluid, the medium after 1 change, and the medium during culturing and before transplantation. Skin donors for cell cultures were assigned to the groups based on if the skin was collected up to 7 days following the burn or later. On average, 12% of the disqualifications were reported among donors for cell culturing. The most frequent cause of donor disqualification (54% of all disqualifications) was a positive HBc(+). The occurrence of fungal infections detected in the cellular material was over 30%. Establishing the culture after day 7 following the injury immediately increases the risk of infection by 25% in comparison to those cultures established before or on day 7 following the injury. Proper disinfection of donor place is crucial, but sometimes insufficient for maintenance sterility in cell culture. The risk of infection increases 25% after 7 following the injury.

Simultaneous Vitreoretinal Surgery and Penetrating Keratoplasty without a Keratoprosthesis or Endoscopy for Vitreoretinal Disease Associated with Corneal Opacity

We evaluated the visual outcome of combined penetrating keratoplasty (PKP) and 25G pars plana vitrectomy (PPV) performed without a temporary keratoprosthesis or endoscopy in a patient with vitreoretinal disease complicated by severe corneal opacity. The patient was a 68-year-old woman who had severe corneal opacity and silicone oil in her left eye after several previous intraocular surgeries for rhegmatogenous retinal detachment and proliferative vitreoretinopathy. We successfully performed a combined surgery of conventional PKP followed by 25G PPV without the use of a keratoprosthesis. At 6 months after surgery, visual acuity had not improved, and the density of corneal endothelial cells of the donor cornea had declined from 3,205 to 1,969 cells/mm². However, corneal transparency remained good, and additional surgery for vitreoretinal disease was not necessary. The combined surgical procedure designed to minimize the number of open-sky steps and to limit vitreoretinal complications thus proved to be safe and achieved stable corneal clarity in a patient with vitreoretinal disease and severe corneal opacity.

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

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

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.

A standardized methodology for longitudinal assessment of corneal endothelial morphometry in eye banked corneas

Eye banked research-grade human donor corneas serve as principal ex vivo source for studying the mechanisms that underlie corneal endothelial cell damage/death and survival. Wide-field specular microscopy can be used for corneal endothelial visualization and allows for indirect assessment of endothelial cell function by analyzing endothelial cell density and morphometric parameters. However, a standardized approach is needed to observe corneal endothelial changes over time. This protocol describes reliable ex vivo methods for consecutive analyses of human donor corneal endothelial cell density and morphometric parameters change using a wide-field dual imaging specular microscope. This protocol involves tissue warming, acquisition and analysis of specular endothelial images, assessment of corneal layers with the new Enhance mode, optical pachymetry measurement, and qualitative image quality grading scales. This quantitative and qualitative evaluation of donor corneas allows for a systematic analysis of endothelial dynamic responses to ex vivo induced stress and can be used as a valuable tool to better elucidate specular findings and mechanisms mediating corneal endothelial cell loss in corneal disease and after transplantation.

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

Importance

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

Objective

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

Design, Setting, and Participants

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

Interventions

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

Main Outcomes and Measures

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

Results

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

Conclusions and Relevance

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

Immune privilege in corneal transplantation

Corneal transplantation is the most successful solid organ transplantation performed in humans. The extraordinary success of orthotopic corneal allografts, in both humans and experimental animals, is related to the phenomenon of "immune privilege". Inflammation is self-regulated to preserve ocular functions because the eye has immune privilege. At present, three major mechanisms are considered to provide immune privilege in corneal transplantation: 1) anatomical, cellular, and molecular barriers in the cornea; 2) tolerance related to anterior chamber-associated immune deviation and regulatory T cells; and 3) an immunosuppressive intraocular microenvironment. This review describes the mechanisms of immune privilege that have been elucidated from animal models of ocular inflammation, especially those involving corneal transplantation, and its relevance for the clinic. An update on molecular, cellular, and neural interactions in local and systemic immune regulation is provided. Therapeutic strategies for restoring immune privilege are also discussed.