Corneal thickness as a predictor of corneal transplant outcome

Long-Term Monitoring of Corneal Grafts Via Anterior Segment OCT Pachymetry Maps

Purpose

To assess the efficacy of anterior segment OCT (AS-OCT) in the long-term monitoring of corneal grafts and its integration into a hybrid remote care model for early detection and management of graft rejection or failure.

Design

Prospective cohort study.

Participants

Seventy-four patients (93 eyes) who underwent corneal transplantation from October 2021 to December 2023, with a follow-up period of ≥6 months.

Methods

Serial AS-OCT pachymetry maps and cross-sectional scans were performed at fixed postoperative intervals, and the findings were correlated with clinical signs of graft rejection or failure on slit lamp examination for thickness changes >50 μm. A hybrid remote AS-OCT screening protocol was initiated 1 week postoperatively.

Main Outcome Measures

Diagnostic accuracy of AS-OCT, measured by specificity and sensitivity, in detecting graft rejection or failure through changes in corneal and graft thickness.

Results

Anterior segment OCT demonstrated high diagnostic accuracy with a specificity of 97.6% and a sensitivity of 88.9% in detecting graft rejection or failure. The mean central corneal thickness increase in cases resulting in graft rejection or failure was 82.7 ± 21.5 μm, a thickness change that is not discernible by slit lamp examination alone. The utility of AS-OCT in a hybrid remote monitoring model was demonstrated through 3 detailed case studies, highlighting improved clinical workflow and patient convenience without compromising postoperative outcomes.

Conclusions

Serial AS-OCT imaging serves as a robust, objective, and quantitative tool for postoperative surveillance of corneal grafts, significantly benefiting patient outcomes by allowing timely interventions. Integration of AS-OCT into a hybrid remote screening protocol supports comprehensive monitoring, complementing direct clinical evaluations and optimizing postoperative care.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Immune responses in rodent whole eye transplantation: elucidation and preliminary investigations into rejection diagnosis and monitoring

Background

Whole Eye Transplantation (WET) offers potential for vision restoration but is hindered by the complex challenge of immune rejection. Understanding and closely monitoring these immunological responses is crucial for advancing WET. This study delves into the timeline and nature of immune responses in a rodent model of WET without immunosuppression, aiming to elucidate a detailed picture of the immune landscape post-transplantation and establish innovative diagnostic and monitoring methods.

Methods

We employed a multi-faceted approach to analyze immune responses post-WET, including assessments of gross changes in corneal transparency, thickness, and skin condition. Histopathological examinations of both ocular and surrounding skin tissues provided insights into cellular changes, complemented by ocular RT-qPCR for molecular analysis. Serological analysis was employed to quantify cytokines, chemokines, and donor-specific antibodies, aiming to identify potential biomarkers correlating with WET rejection and to validate the presence of antibody-mediated rejection. These methodologies collectively contribute to the development of non-invasive diagnostic and monitoring strategies for WET.

Results

Our study revealed a rapid and acute immune response following WET, characterized by an early innate immune response dominated by complement involvement, and infiltration of neutrophils and monocytes by post-operative day (POD) 2. This was succeeded by an acute T-cell-mediated immune reaction, predominantly involving T helper 1 (Th1) cells and cytotoxic T lymphocytes (CTLs). The presence of donor specific antibody (DSA) and indications of pyroptosis in the early phases of rejection were observed. Notably, the early elevation of serum CXCL10 by POD4, coupled with ocular CD3+ cell infiltration, emerged as a potential early biomarker for WET rejection. Additionally, corneal transparency grading proved effective as a non-invasive monitoring tool.

Conclusion

This study offers a first-time comprehensive exploration of immune responses in WET, unveiling rapid and complex rejection mechanisms. The identification of early biomarkers and the development of non-invasive monitoring techniques significantly advance our understanding of WET rejection. Additionally, these findings establish an essential baseline for future research in this evolving field.

Impact of Donor, Host, and Surgical Parameters on High Endothelial Cell Density More Than 5 Years after Penetrating Keratoplasty

OBJECTIVES

To investigate the correlation between postoperative endothelial cell loss (ECL) and donor, host, and surgical parameters, and to assess the clinical impact of maintaining a high endothelial cell density (ECD) of ≥ 1500 cells/mm2 5 years after penetrating keratoplasty (PKP).

METHODS

This retrospective cohort study included 216 eyes with 5 years of follow-up, of which 94 had annual visits, and who underwent normal-risk elective PKP for noninfectious indications by one corneal microsurgeon (B. S.) between 2009 and 2016.

RESULTS

Among the 216 eyes, ECL (39.1%) over 5 years postoperative exhibited weak positive correlations with storage solution time (p = 0.024) and postmortem time (p = 0.028), and moderately positively correlations with the preoperative ECD (p < 0.001). The 5-year postoperative ECL differed significantly between in domo-prepared (36.8%) and ex domo donor corneas (46.3%; p = 0.001). In the 94 eyes, no significant differences were found between the two groups for central pupil pachymetry (CCT) and BCVA (p > 0.074). However, CCT increased significantly between 1 and 4 years (p = 0.034) and 1 and 5 years postoperatively (p = 0.012), respectively. BCVA improved significantly at 1 year postoperatively and continued to improve until 2 years postoperatively (p < 0.001).

CONCLUSION

The Lions corneal bank Saar-Lor-Lux achieved a significantly reduced ECL (36.8%) over 5 years compared to ex domo donor corneas (46.3%). A weak positive correlation was found between ECL with the storage solution time and the postmortem time, as well as a moderate positive correlation with the preoperative ECD. Although CCT increased significantly over 5 years, BCVA improved significantly from the first to the second postoperative year and remained stable thereafter.

An Overview of Corneal Transplantation in the Past Decade

The cornea is a transparent avascular structure located in the front of the eye that refracts light entering the eyes and also serves as a barrier between the outside world and the internal contents of the eye. Like every other body part, the cornea may suffer insult from trauma, infection, and inflammation. In the case of trauma, a prior infection that left a scar, or conditions such as keratoconus that warrant the removal of all or part of the cornea (keratoplasty), it is important to use healthy donor corneal tissues and cells that can replace the damaged cornea. The types of cornea transplant techniques employed currently include: penetrating keratoplasty, endothelial keratoplasty (EK), and artificial cornea transplant. Postoperative failure acutely or after years can result after a cornea transplant and may require a repeat transplant. This minireview briefly examines the various types of corneal transplant methodologies, indications, contraindications, presurgical protocols, sources of cornea transplant material, wound healing after surgery complications, co-morbidities, and the effect of COVID-19 in corneal transplant surgery.

Dropless penetrating keratoplasty using a subconjunctival dexamethasone implant: safety pilot study

BACKGROUND/AIM

Rejection is the main cause of graft failure after penetrating keratoplasty (PK). Its prevention by repeated instillation of steroid eye-drops has not evolved in decades. Poor adherence and discontinuous nature of eye-drop treatment may explain some PK failures. In a rabbit model, we previously demonstrated that a subconjunctival dexamethasone implant was well tolerated and prevented rejection efficiently in the first 5-6 weeks. This clinical trial investigates its tolerance and safety after PK.

METHODS

Single-centre, phase II non-randomised tolerance and safety pilot study (NCT02834260). Designed to analyse the risk of elevated intraocular pressure (IOP), discomfort and resorption time. Fourteen patients with a low rejection risk indication of PK were enrolled between January 2017 and August 2018. The implant was injected in the 12 o'clock position, 5 mm from the limbus, at the end of PK. A steroid eye-drop treatment was planned when implant resorption was complete. Patients were monitored regularly for 12 months: IOP (main outcome measure at 1 month), discomfort and redness scores, implant status, rejection episode and central corneal thickness by optical coherence tomography. An independent data safety monitoring committee verified safety aspects.

RESULTS

No increase in IOP or other adverse event related to the implant was observed. Average resorption time was 6 weeks. The switch to steroid eye-drops was uneventful. One patient, included despite preoperative corneal neovascularisation (unintended protocol deviation) experienced a rejection.

CONCLUSIONS

This is the first proof of concept that dropless immunosuppression is possible after low rejection risk PK.

TRIAL REGISTRATION NUMBER

NCT02834260.

Comparison of central corneal thickness in healthy eyes using ultrasound pachymetry, non-contact specular microscopy and a high-resolution Scheimpflug camera

PURPOSE

To compare and analyze the interchangeability in measuring central corneal thickness (CCT) using ultrasonic pachymetry (USP, PACHMATE 2, DGH, Inc, Exton, PA, USA), non-contact specular microscopy (NCSM, CEM-530, Nidek CO, LTD, Gamagori, Japan) and a high-resolution Scheimpflug Camera (Pentacam HR, OCULUS, Wetzlar, Germany).

METHODS

An observational, cross-sectional study was performed recruiting 216 volunteers, for a sample size of 216 eyes with no ocular abnormalities other than refractive errors. All subjects underwent pachymetric measurements obtained by USP, NCSM and Pentacam HR. Examinations were performed by the same examiner with USP always following the noncontact examinations.

RESULTS

The mean CCT (± SD) was 560.30 ± 38.80 μm, 556.76 ± 36.83 μm and 547.31 ± 35.28 μm for USP, NCSM and Pentacam HR, respectively. The Bland-Altman analysis showed that the highest concordance was found between USP and NCSM, with differences between - 13.18 μm and 20.26 μm. For the differences between measurements obtained with Pentacam HR and USP, the differences at Bland-Altman plot were between - 28.25 and 13.57 μm. The lowest concordance was found for the CCT values measured with Pentacam HR and NCSM, with differences between - 25.67 and 6.86 μm. The intraclass correlation coefficient (ICC) between all pairs of measurements was between 0.979 and 0.987, suggesting that the mean measurements were strongly correlated.

CONCLUSION

Measurements obtained with all three devices had high correlation. USP and NCSM were found in good agreement and high concordance, too. The above results indicate that these two devices are interchangeable in clinical practice. Pentacam HR may be a useful alternative for measuring CCT; however, it significantly underestimates CCT and cannot be used interchangeably with the other devices that we studied.

Postoperative, but not preoperative, central corneal thickness correlates with the postoperative visual outcomes of Descemet membrane endothelial keratoplasty

Descemet membrane endothelial keratoplasty (DMEK) restores visual acuity in patients with progressive corneal endothelial diseases such as Fuchs endothelial corneal dystrophy (FECD). However, patients often prefer to delay the surgery as long as possible, even though outcomes are poorer in advanced FECD. A recent study proposed that preoperative central corneal thickness (CCT) of ≥625 μm associated with worse best spectacle-corrected visual acuity (BSCVA) after DMEK for FECD. Since this threshold could signal to both surgeons and patients when to perform DMEK, we further explored the relationship between CCT and BSCVA with a retrospective cohort study. The cohort consisted of all patients with FECD who underwent DMEK in a tertiary-care hospital in 2015-2020 and were followed for 12 months. Extremely decompensated corneas were not included. Relationships between preoperative CCT and BSCVA on days 8 and 15 and months 1, 3, 6, and 12 were examined with Pearson correlation analyses. Eyes with preoperative CCT <625 or ≥625 μm were also compared in terms of postoperative BSCVA. Relationships between postoperative CCT and final BSCVA were also explored. The cohort consisted of 124 first-operated eyes. Preoperative CCT did not correlate with postoperative BSCVA at any timepoint. Eye subgroups did not differ in postoperative BSCVA. However, postoperative CCT at 1-12 months correlated significantly with 12-month BSCVA (r = 0.29-0.49, p = 0.020-0.001). Thus, postoperative, but not preoperative, CCT correlated with postoperative BSCVA. This phenomenon may reflect factors that distort preoperative CCT measurements but disappear after surgery. This observation and our analysis of the literature suggest that while there is a relationship between CCT and post-DMEK visual acuity, preoperative CCT measurements may not always adequately reflect that relationship and may therefore not be a reliable predictor of DMEK visual outcomes.

Risk factors of rejection after penetrating keratoplasty: a retrospective monocentric study

PURPOSE

To assess risk factors of rejection after penetrating keratoplasty (PKP).

METHODS

This retrospective monocentric study assessed risk factors for rejection in patients who underwent PKP at Montpellier University Hospital between June 2005 and September 2018. Graft and donor data were obtained from our tissue bank in Montpellier. Clinical data of recipients were recorded from medical files. Survival was estimated by the Kaplan-Meir method. Potential risk factors of rejection were assessed by multivariate Cox proportional hazards analysis, estimating hazard ratios (HR) and 95% confidence intervals (CI).

RESULTS

Among the 316 consecutive patients (59% male, mean SD] age 52 [17]), 360 eyes underwent PKP. Indications for PKP were bullous keratopathy (27%), infectious keratitis (20%), and keratoconus (15%). The median follow-up was 44 months (IQR 22-73). The overall graft survival and irreversible rejection rate at 5 years were 70% and 29%, respectively. Factors associated with risk of rejection were prior indication for graft rejection (SHR [CI 95%] = 7.8 [2.6-23.1]), trauma (SHR [CI 95%] = 3.6 [1.1-11.7]), and infectious keratitis (SHR [CI 95%] = 2.7 [1.2-11.1]), history of corneal neovascularization (SHR [CI 95%] = 2.1 [1.2-3.8]), hypertonia (SHR [CI 95%] = 2.8 [1.8-4.3]), and mixed sex matching (SHR [CI 95%] = 2.0 [1.01-4.0]).

CONCLUSION

The significant risk factors of graft rejection after PKP found in this study agree with those from major international cohorts: prior indication for graft rejection, history of neovascularization and high intraocular pressure. Sex matching donor-recipient is a most recent parameter in the literature confirmed by the present analysis.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT04791696.

Prediction of corneal graft rejection using central endothelium/Descemet's membrane complex thickness in high-risk corneal transplants

To determine whether measurements of Endothelium/Descemet complex thickness (En/DMT) are of predictive value for corneal graft rejection after high-risk corneal transplantation, we conducted this prospective, single-center, observational case series including sixty eyes (60 patients) at high risk for corneal graft rejection (GR) because of previous immunologic graft failure or having at least two quadrants of stromal vascularization. Patients underwent corneal transplant. At 1st, 3rd, 6th, 9th, and 12th postoperative month, HD-OCT imaging of the cornea was performed, and the corneal status was determined clinically at each visit by a masked cornea specialist. Custom-built segmentation tomography algorithm was used to measure the central En/DMT. Relationships between baseline factors and En/DMT were explored. Time dependent covariate Cox survival regression was used to assess the effect of post-operative En/DMT changes during follow up. A longitudinal repeated measures model was used to assess the relationship between En/DMT and graft status. Outcome measures included graft rejection, central Endothelium/Descemet's complex thickness, and central corneal thickness (CCT). In patients with GR (35%), the central En/DMT increased significantly 5.3 months (95% CI: 2, 11) prior to the clinical diagnosis of GR, while it remained stable in patients without GR. During the 1-year follow up, the rejected grafts have higher mean pre-rejection En/DMTs (p = 0.01), compared to CCTs (p = 0.7). For En/DMT ≥ 18 µm cut-off (at any pre-rejection visit), the Cox proportional hazard ratio was 6.89 (95% CI: 2.03, 23.4; p = 0.002), and it increased to 9.91 (95% CI: 3.32, 29.6; p < 0.001) with a ≥ 19 µm cut-off. In high-risk corneal transplants, the increase in En/DMT allowed predicting rejection prior to the clinical diagnosis.

Clinical Outcomes of Micropulse Transscleral Cyclophotocoagulation in Patients with a History of Keratoplasty

Purpose

To examine the surgical outcomes and graft conditions in patients receiving micropulse transscleral cyclophotocoagulation (MP-TSCPC) to treat post-keratoplasty ocular hypertension.

Methods

This retrospective observational study included 30 eyes of 28 consecutive glaucoma patients with a history of penetrating keratoplasty (PKP) or Descemet's stripping automated endothelial keratoplasty (DSAEK) who underwent MP-TSCPC at the University of California, San Francisco from 09/2015 to 08/2018. Using the Wilcoxon signed-rank test, we compared preoperative and postoperative intraocular pressure (IOP), number of glaucoma medications, visual acuity, and central corneal thickness at 1, 3, 6, and 12 months. Postoperative complications, additional surgeries, and graft failures were also recorded at these follow-up times. Linear regression model was used to study whether PKP vs. DSAEK affects the effectiveness of MP-TSCPC.

Results

Thirty eyes from 28 patients were followed for 12 months. IOP was significantly decreased from preop at all follow-up points (P < 0.001). There was no significant change in the number of glaucoma drops, visual acuity, or CCT. At 12 months, 21 of the 30 eyes met the definition of success, and only one underwent repeat PKP due to graft rejection. The type of corneal transplant was not a significant factor for IOP reduction at the last follow-up.

Conclusions

MP-TSCPC achieved desirable IOP control and success rates for postkeratoplasty patients while resulting in minimal complications and graft failure. It appears to be a safe and effective procedure in patients who received corneal transplant with one-year follow-up.

Variable Responses to Corneal Grafts: Insights from Immunology and Systems Biology

Corneal grafts interact with their hosts via complex immunobiological processes that sometimes lead to graft failure. Prediction of graft failure is often a tedious task due to the genetic and nongenetic heterogeneity of patients. As in other areas of medicine, a reliable prediction method would impact therapeutic decision-making in corneal transplantation. Valuable insights into the clinically observed heterogeneity of host responses to corneal grafts have emerged from multidisciplinary approaches, including genomics analyses, mechanical studies, immunobiology, and theoretical modeling. Here, we review the emerging concepts, tools, and new biomarkers that may allow for the prediction of graft survival.

Comparison of corneal thickness in patients with dry eye disease using the Pentacam rotating Scheimpflug camera and anterior segment optical coherence tomography

The purpose of this study was to compare central corneal thickness, thinnest corneal thickness, and the thinnest point of the cornea between Pentacam and anterior segment optical coherence tomography (ASOCT) in patients with dry eye disease (DED). This cross-sectional study included 195 participants between November 2015-June 2017. DED was diagnosed using the Asia Dry Eye Society criteria and further divided into mild and severe DED based on kerato-conjunctival vital staining. Central corneal thickness, thinnest corneal thickness, and the thinnest point of the cornea measured by Pentacam and ASOCT were compared, and Pearson's correlation coefficients were estimated. The differences in central corneal thickness and the thinnest corneal thickness between Pentacam and ASOCT were analysed using Bland-Altman and multivariate regression analyses adjusted for age and sex. This study included 70 non-DED subjects and 52 patients with mild and 73 with severe DED. The Pentacam and ASOCT measurements of central corneal thickness and thinnest corneal thickness were strongly correlated, but the respective values were higher when measured with Pentacam. The Bland-Altman analysis revealed differences in central corneal thickness (non DED, 11.8; mild DED, 13.2; severe DED, 19.6) and in thinnest corneal thickness (non DED, 13.1; mild DED, 13.4; severe DED, 20.7). After adjusting for age and sex, the differences in central corneal thickness (β = 7.029 μm, 95%CI 2.528-11.530) and thinnest corneal thickness (β = 6.958 μm, 95%CI 0.037-13.879) were significantly increased in the severe-DED group. The distribution of the thinnest point of the cornea in the cornea's inferior temporal quadrant between Pentacam and ASOCT deviated in severe DED (Pentacam: 90.4% vs. ASOCT: 83.6%). Clinicians should consider that there were significant differences in corneal-morphology assessment between the measurements with Pentacam and ASOCT in severe DED.

Diagnostic Performance of Three-Dimensional Endothelium/Descemet Membrane Complex Thickness Maps in Active Corneal Graft Rejection

PURPOSE

To evaluate the performance of 3-dimensional (3D) endothelium/Descemet membrane complex thickness (En/DMT) maps vs total corneal thickness (TCT) maps in the diagnosis of active corneal graft rejection.

DESIGN

Cross-sectional study.

METHODS

Eighty-one eyes (32 clear grafts and 17 with active rejection, along with 32 age-matched control eyes) were imaged using high-definition optical coherence tomography (HD-OCT), and a custom-built segmentation algorithm was used to generate 3D color-coded maps of TCT and En/DMT of the central 6-mm cornea. Regional En/DMT and TCT were analyzed and compared between the studied groups. Receiver operating characteristic curves were used to determine the accuracy of En/DMT and TCT maps in differentiating between studied groups. Main outcome measures were regional En/DMT and TCT.

RESULTS

Both regional TCT and En/DMT were significantly greater in actively rejecting grafts compared to both healthy corneas and clear grafts (P < .001). Using 3D thickness maps, central, paracentral, and peripheral En/DMT achieved 100% sensitivity and 100% specificity in diagnosing actively rejecting grafts (optimal cut-off value [OCV] of 19 μm, 24 μm, and 26 μm, respectively), vs only 82% sensitivity and 96% specificity for central TCT, OCV of 587 μm. Moreover, central, paracentral, and peripheral En/DMT correlated significantly with graft rejection severity (r = 0.972, r = 0.729, and r = 0.823, respectively; P < .001).

CONCLUSION

3D En/DMT maps can diagnose active corneal graft rejection with excellent accuracy, sensitivity, and specificity. Future longitudinal studies are required to evaluate the predictive and prognostic role of 3D En/DMT maps in corneal graft rejection.

Comparison of endothelial/Descemet's membrane complex thickness with endothelial cell density for the diagnosis of corneal transplant rejection

Purpose:

This study compared the effectiveness of endothelial/Descemet’s membrane complex thickness obtained using high-definition anterior segment optical coherence tomography with endothelial cell density obtained using confocal microscopy as diagnostic tools in predicting corneal transplant rejection.

Methods:

This observational, prospective, cross-sectional study evaluated penetrating keratoplasty grafts. Slit lamp examination organized the grafts into healthy or rejecting grafts. Grafts were scanned using both high-definition anterior segment optical coherence tomography and confocal microscopy. Central corneal thickness, endothelial/Descemet’s membrane complex thickness, endothelial cell density, and coefficient of variation were each compared with the clinical status. Descemet’s rejection index, defined by endothelial/Descemet’s membrane complex thickness divided by central corneal thickness multiplied by 33, further compared endothelial/Descemet’s membrane complex thickness with central corneal thickness.

Results:

Endothelial/Descemet’s membrane complex thickness, central corneal thickness, and Descemet’s rejection index were all able to differentiate between clear and rejected corneal grafts (p < 0.0001, p = 0.001, and p = 0.012, respectively). Endothelial cell density and coefficient of variation did not correlate with the clinical status (p = 0.054 and p = 0.102, respectively). Endothelial/Descemet’s membrane complex thickness had the largest area under the curve using receiver operating characteristic curves (p < 0.0001). Endothelial/Descemet’s membrane complex thickness had a sensitivity of 86% and specificity of 81% with a cutoff value of >16.0 µm (p < 0.0001). The sensitivity and specificity of endothelial cell density were both 71% with a cutoff value of ⩽897 cells/mm² (p = 0.053). There was a high correlation between endothelial/Descemet’s membrane complex thickness and both Descemet’s rejection index and central corneal thickness (p < 0.0001).

Conclusion:

Endothelial/Descemet’s membrane complex thickness measured by high-definition anterior segment optical coherence tomography is a useful parameter for the diagnosis of corneal graft rejection. The diagnostic performance of endothelial/Descemet’s membrane complex thickness was significantly better than that of endothelial cell density and central corneal thickness. Endothelial cell density and the coefficient of variation were unable to diagnose corneal graft rejection in our cross-sectional study.

Accuracy of Corneal Thickness by Swept-Source Optical Coherence Tomography and Scheimpflug Camera in Virgin and Treated Fuchs Endothelial Dystrophy

PURPOSE

To assess intraobserver repeatability, intersession reproducibility, and agreement of swept-source Fourier-domain optical coherence tomography (SS-OCT) and the Scheimpflug camera in measuring corneal thickness in virgin and grafted eyes with Fuchs endothelial corneal dystrophy (FECD).

METHODS

Thirty-six control eyes, 35 FECD eyes, 30 FECD with corneal edema eyes, 25 Descemet stripping automated endothelial keratoplasty (DSAEK) eyes, and 29 Descemet membrane endothelial keratoplasty (DMEK) eyes were included. The apical center, pupillary center, and thinnest corneal thickness were determined in 3 consecutive images and repeated 2 weeks later. Repeatability and reproducibility coefficients, intraclass correlation coefficients, and 95% limits of agreement (LOA) between measurements were calculated. Agreement between devices was assessed using Bland-Altman analysis.

RESULTS

Corneal thickness measurements were highly reproducible and repeatable with both systems. SS-OCT showed better repeatability in all corneal locations in the normal, FECD, FECD with edema, DSAEK, and DMEK groups (coefficient of variation ≤0.60%, ≤0.36%, ≤0.43%, ≤1.09%, and ≤0.48%, respectively) than the Scheimpflug (coefficient of variation ≤1.15%, ≤0.92%, ≤1.10%, ≤1.25%, and ≤1.14%, respectively). Between-session 95% LOA for SS-OCT was less than 3% for all groups except for the FECD with edema group, being almost double using the Scheimpflug camera. Differences between instruments were statistically significant in all groups and locations (P < 0.01) except in the DSAEK group (P ≤ 0.51); however, SS-OCT underestimated all measurements.

CONCLUSIONS

SS-OCT provides better reproducible and repeatable measurements of corneal thickness than those obtained with the Scheimpflug camera in patients with FECD or an endothelial transplant. Variations between examinations higher than the 95% LOA observed in our study should raise awareness of changes in the endothelial function.

Repeatability and Intersession Reproducibility of Pentacam Corneal Thickness Maps in Fuchs Dystrophy and Endothelial Keratoplasty

PURPOSE

To assess intrasession repeatability and intersession reproducibility of Pentacam corneal thickness maps in patients with Fuchs endothelial corneal dystrophy (FECD) before and after endothelial transplantation.

METHODS

In this observational diagnostic evaluation, 20 healthy subjects along with 81 consecutive patients were examined. Patients were classified into 4 groups: FECD without corneal edema, FECD with corneal edema, Descemet stripping automated endothelial keratoplasty, and Descemet membrane endothelial keratoplasty. Three consecutive scans of each eye were obtained at 2 different sessions. Raw pachymetry data were used to calculate average values of 4 concentric annular zones, which were also divided into 8 sectors. Repeatability and reproducibility coefficients (CR), coefficient of variation (CV), intraclass correlation coefficient, and 95% limits of agreement were calculated.

RESULTS

The intrasession repeatability CV was ≤1% in the central 6 mm for all groups, with an intraclass correlation coefficient ≥0.97. It was better at the central zone than the periphery in all groups. Intersession reproducibility tended to be worse in the central area than the periphery in FECD without edema (CR ≤ 24.37; CV ≤ 1.48) and FECD with edema (CR ≤ 36.74; CV ≤ 2.03), whereas it was better in the central area in healthy eyes (CR ≤ 20.11; CV ≤ 1.32) and improved after Descemet stripping automated endothelial keratoplasty (CR ≤ 21.93; CV ≤ 1.31) and Descemet membrane endothelial keratoplasty (CR ≤ 30.83; CV ≤ 1.94).

CONCLUSIONS

Pentacam corneal thickness maps showed good repeatability and intersession reproducibility in virgin and grafted corneas with FECD, which makes it a valid tool for monitoring these patients. Central areas showed the highest variability between sessions in diseased groups.

Cyclosporine a drug-delivery system for high-risk penetrating keratoplasty: Stabilizing the intraocular immune microenvironment

Cyclosporine A (CsA) is an essential medication used to prevent corneal allograft rejection. Our preliminary studies revealed that CsA drug-delivery system (DDS) was more effective in preventing high-risk corneal allograft rejection than topical CsA application. However, the impacts of CsA DDS on the intraocular immune microenvironment were not fully elucidated. In the present study, we investigated the effect of CsA DDS on the cornea allograft, aqueous humor, and iris-ciliary body using a rabbit model of high-risk penetrating keratoplasty. New Zealand white rabbits were divided into four groups: a normal control group, an untreated group, a CsA eye drop group and a CsA DDS group. Graft survival was monitored for 12 weeks, and the therapeutic effects of CsA DDS were evaluated at 3 and 12 weeks after high-risk keratoplasty. In the CsA DDS group, the mean graft survival time was significantly prolonged when compared with the untreated and CsA eye drop groups. At all time-points, Langerhans cell density, inflammatory cell density, and central corneal thickness in the CsA DDS group were much lower(all p < 0.01) than the untreated and CsA eye drop groups, in which their parameters were significantly higher than the normal control group (all p < 0.01). Compared with the untreated and CsA eye drop groups, an implanted CsA DDS markedly decreased the CD11b+ and CD8+ T cell infiltration in the corneal grafts. CsA DDS treatment also greatly reduced the CD4+ T cell density and the expression of interferon-gamma, interleukin-2 (IL-2), IL-6, CD80, and CD86 mRNA both in the corneal graft and iris-ciliary body (all p < 0.01). Moreover, CsA DDS significantly reduced the IL-2 level in aqueous humor (p < 0.01). Taken together, our results suggest that CsA DDS implanted into the anterior chamber create a relative immunosuppressive microenvironment in the corneal graft, iris-ciliary body, and aqueous humor. Stabilizing the intraocular immune microenvironment could partially elucidate the mechanism of CsA DDS in suppressing corneal graft rejection.

Safety and Efficacy of OXB-202, a Genetically Engineered Tissue Therapy for the Prevention of Rejection in High-Risk Corneal Transplant Patients

Due to both the avascularity of the cornea and the relatively immune-privileged status of the eye, corneal transplantation is one of the most successful clinical transplant procedures. However, in high-risk patients, which account for >20% of the 180,000 transplants carried out worldwide each year, the rejection rate is high due to vascularization of the recipient cornea. The main reason for graft failure is irreversible immunological rejection, and it is therefore unsurprising that neovascularization (NV; both pre and post grafting) is a significant risk factor for subsequent graft failure. NV is thus an attractive target to prevent corneal graft rejection. OXB-202 (previously known as EncorStat^®) is a donor cornea modified prior to transplant by ex vivo genetic modification with genes encoding secretable forms of the angiostatic human proteins, endostatin and angiostatin. This is achieved using a lentiviral vector derived from the equine infectious anemia virus called pONYK1EiA, which subsequently prevents rejection by suppressing NV. Previously, it has been shown that rabbit donor corneas treated with pONYK1EiA substantially suppress corneal NV, opacity, and subsequent rejection in an aggressive rabbit model of cornea graft rejection. Here, efficacy data are presented in a second rabbit model, which more closely mirrors the clinical setting for high-risk corneal transplant patients, and safety data from a 3-month good laboratory practice toxicology and biodistribution study of pONYK1EiA-modified rabbit corneas in a rabbit corneal transplant model. It is shown that pONYK1EiA-modified rabbit corneas (OXB-202) significantly reduce corneal NV and the rate of corneal rejection in a dose-dependent fashion, and are tolerated with no adverse toxicological findings or significant biodistribution up to 13 weeks post surgery in these rabbit studies. In conclusion, angiogenesis is a valid target to prevent corneal graft rejection in a high-risk setting, and transplanted genetically modified corneas are safe and well-tolerated in an animal model. These data support the evaluation of OXB-202 in a first-in-human trial.

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

PURPOSE

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

DESIGN

Diagnostic reliability study.

METHODS

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

RESULTS

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

CONCLUSIONS

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

Descemet membrane endothelial keratoplasty for graft failure following penetrating keratoplasty

PURPOSE

Descemet membrane endothelial keratoplasty (DMEK) is superior to penetrating keratoplasty (PK) in terms of visual rehabilitation, intraoperative safety and risk of rejection. Therefore, it seems reasonable to perform DMEK in eyes with endothelial failure following PK. We herein report our first clinical results.

METHODS

Nineteen eyes with endothelial graft failure following PK were treated with DMEK. The majority of these eyes (12) had limited visual potential. The major indication for DMEK was pain relief in patients with bullous keratopathy. Visual acuity (VA), central corneal thickness (CCT), rate of graft dislocations, graft survival, graft rejections and other complications were extracted from the medical records.

RESULTS

Although comorbidities limiting VA were present in 12 of the 19 eyes, VA increased from 0.05 to 0.1 (median) in 16 eyes. CCT decreased substantially (range 63-363 μm). Rebubbling was necessary in five eyes with incomplete graft adherence. There were two immunologic graft reactions and three graft failures. No major complications like endophthalmitis or expulsive bleeding occurred.

CONCLUSIONS

DMEK is feasible to treat endothelial graft failure following PK. This is even true for eyes with limited visual potential.

Sugar A, Gal RL, Kollman C, Raghinaru D, Dontchev M, Croasdale CR, Feder RS, Holland EJ, Lass JH, Macy JI, Mannis MJ, Smith PW, Soukiasian SH, Beck RW. Factors associated with corneal graft survival in the cornea donor study

IMPORTANCE

The Cornea Donor Study (CDS) showed that donor age is not a factor in survival of most penetrating keratoplasties for endothelial disease. Secondary analyses confirm the importance of surgical indication and presence of glaucoma in outcomes at 10 years.

OBJECTIVE

To assess the relationship between donor and recipient factors and corneal graft survival in the CDS.

DESIGN, SETTING, AND PARTICIPANTS

Multicenter prospective, double-masked, controlled clinical trial conducted at 80 clinical sites. One hundred five surgeons enrolled 1090 participants undergoing corneal transplant for a moderate-risk condition, principally Fuchs dystrophy or pseudophakic or aphakic corneal edema (PACE). Forty-three eye banks provided corneas.

INTERVENTIONS

Corneas from donors younger than 66 years and donors 66 years or older were assigned, masked to donor age. Surgery and postoperative care were performed according to the surgeons' usual routines. Participants were followed up for as long as 12 years.

MAIN OUTCOMES AND MEASURES

Graft failure, defined as a regrafting procedure or a cloudy cornea for 3 consecutive months.

RESULTS

The 10-year cumulative probability of graft failure was higher in participants with PACE than in those with Fuchs dystrophy (37% vs 20%; hazard ratio [HR], 2.1 [99% CI, 1.4-3.0]; P < .001) and in participants with a history of glaucoma before penetrating keratoplasty, particularly with prior glaucoma surgery (58% with prior glaucoma surgery and use of medications to lower intraocular pressure at the time of surgery vs 22% with no history of glaucoma surgery or medication use; HR, 4.1 [99% CI, 2.2-7.5]; P < .001). We found trends toward increased graft failure in recipients who were 70 years or older compared with those younger than 60 years (29% vs 19%; HR, 1.2 [99% CI, 0.7-2.1]; P = .04) or were African American (HR, 1.5; P = .11) or who had a history of smoking (35% vs 24%; HR, 1.6 [99% CI, 0.9-2.8]; P = .02). Lower endothelial cell density (ECD) and higher corneal thickness (CT) at 6 months (6% vs 41% for ECD ≥2700 vs <1700 cells/mm2 [P < .001]; 14% vs 36% for CT <500 vs ≥600 μm [P = .001]), 1 year (4% vs 39% for ECD ≥2700 vs <1700 cells/mm2 [P < .001]; 18% vs 28% for CT <500 vs ≥600 μm [P = .04]), and 5 years (2% vs 29% for ECD ≥1500 vs <500 cells/mm2 [P < .001]; 7% vs 34% for CT <550 vs ≥650 μm [P < .001]) were associated with subsequent graft failure.

CONCLUSIONS AND RELEVANCE

Most penetrating corneal grafts for Fuchs dystrophy or PACE remain clear at 10 years. The risk for failure is greater for graft recipients with PACE and those with a history of glaucoma. Measurements of ECD and CT during the course of postkeratoplasty follow-up are associated with a risk for failure. However, even with very low ECD and high CT at 5 years, most corneas remain clear at 10 years.

A year of cornea in review: 2013

PURPOSE

The goal of this study was to provide an update of significant corneal literature published in 2013.

DESIGN

This study is a systematic literature review.

METHODS

We conducted a systematic review of the English-language literature published from January 1, 2013, to December 31, 2013, using the following PubMed search and Medical Subject Headings terms: cornea transplantation, keratoplasty, Descemet membrane endothelial keratoplasty, Descemet stripping endothelial keratoplasty, cross linking, pre-Descemet's layer, Rho-associated kinase, keratoprosthesis, infectious keratitis, corneal dystrophy, corneal astigmatism, and keratoconus.

RESULTS

This review summarizes relevant and innovative original articles, review articles, and novel techniques from the following journals: American Journal of Ophthalmology, British Journal of Ophthalmology, Cornea, Graefe's Archive for Clinical and Experimental Ophthalmology, Investigative Ophthalmology & Visual Science, JAMA Ophthalmology, Journal of Cataract and Refractive Surgery, Journal of Refractive Surgery, and Ophthalmology. Case reports, abstracts, letters to the Editor, and unpublished work were excluded, as well as articles e-published ahead of print in 2012 that were discussed in the previous review. One hundred twenty-seven articles met the criteria for this review.

CONCLUSIONS

This review summarizes significant cornea-related literature from 2013.