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

Main issues in penetrating keratoplasty

This review explores contemporary challenges in penetrating keratoplasty (PK), focusing on technical intricacies, technological advancements, and strategies for preventing graft rejection. A systematic literature search from January 2018 to July 2023 was conducted across PubMed, Cochrane, Web of Science, Scopus, and EMBASE. The inclusion criteria comprised studies on PK and its comparison with other corneal pathologies, with emphasis on keratoconus (KC). Two independent reviewers screened studies, extracting relevant data. The review covers PK evolution, highlighting infra-red femtosecond lasers' impact on graft shapes, minimizing astigmatism, and enhancing wound healing. Graft rejection, a primary complication, is examined, detailing risk factors and preventive measures. Preoperative considerations, diagnostic techniques for rejection, and PK in KC are discussed. Postoperative care's significance, including intraocular pressure monitoring and steroid administration, is emphasized. The paper concludes with a comprehensive approach to prevent graft rejection, involving topical and systemic medications. An outlook on evolving monoclonal antibody research is presented. As the field progresses, personalized approaches and ongoing therapeutic exploration are expected to refine strategies, enhancing PK outcomes.

Automated delineation of corneal layers on OCT images using a boundary-guided CNN

Accurate segmentation of corneal layers depicted on optical coherence tomography (OCT) images is very helpful for quantitatively assessing and diagnosing corneal diseases (e.g., keratoconus and dry eye). In this study, we presented a novel boundary-guided convolutional neural network (CNN) architecture (BG-CNN) to simultaneously extract different corneal layers and delineate their boundaries. The developed BG-CNN architecture used three convolutional blocks to construct two network modules on the basis of the classical U-Net network. We trained and validated the network on a dataset consisting of 1,712 OCT images acquired on 121 subjects using a 10-fold cross-validation method. Our experiments showed an average dice similarity coefficient (DSC) of 0.9691, an intersection over union (IOU) of 0.9411, and a Hausdorff distance (HD) of 7.4423 pixels. Compared with several other classical networks, namely U-Net, Attention U-Net, Asymmetric U-Net, BiO-Net, CE-Net, CPFnte, M-Net, and Deeplabv3, on the same dataset, the developed network demonstrated a promising performance, suggesting its unique strength in segmenting corneal layers depicted on OCT images.

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.

Multidisease Deep Learning Neural Network for the Diagnosis of Corneal Diseases

PURPOSE

To report a multidisease deep learning diagnostic network (MDDN) of common corneal diseases: dry eye syndrome (DES), Fuchs endothelial dystrophy (FED), and keratoconus (KCN) using anterior segment optical coherence tomography (AS-OCT) images.

STUDY DESIGN

Development of a deep learning neural network diagnosis algorithm.

METHODS

A total of 158,220 AS-OCT images from 879 eyes of 478 subjects were used to develop and validate a classification deep network. After a quality check, the network was trained and validated using 134,460 images. We tested the network using a test set of consecutive patients involving 23,760 AS-OCT images of 132 eyes of 69 patients. The area under receiver operating characteristic curve (AUROC), area under precision-recall curve (AUPRC), and F1 score and 95% confidence intervals (CIs) were computed.

RESULTS

The MDDN achieved eye-level AUROCs >0.99 (95% CI: 0.90, 1.0), AUPRCs > 0.96 (95% CI: 0.90, 1.0), and F1 scores > 0.90 (95% CI: 0.81, 1.0) for DES, FED, and KCN, respectively.

CONCLUSIONS

MDDN is a novel diagnostic tool for corneal diseases that can be used to automatically diagnose KCN, FED, and DES using only AS-OCT images.

A Novel Network With Parallel Resolution Encoders for the Diagnosis of Corneal Diseases

OBJECTIVE

To propose a deep-learning network for the diagnosis of two corneal diseases: Fuchs' endothlelial dystrophy and keratoconus, based on optical coherence tomography (OCT) images of the cornea.

METHODS

In this paper, we propose a novel network with parallel resolution-specific encoders and composite classification features to directly diagnose Fuchs' endothelial dystrophy and keratoconus using OCT images. Our proposed network consists of a multi-resolution input, multiple parallel encoders, and a composite of convolutional and dense features for classification. The purpose of using parallel resolution-specific encoders is to perform multi-resolution feature fusion. Also, using composite classification features enhances the dense feature learning. We implemented other related networks for comparison with our network and performed k-fold cross-validation on a dataset of 16,721 OCT images. We used saliency maps and sensitivity analysis to visualize our proposed network.

RESULTS

The proposed network outperformed other networks with an image classification accuracy of 0.91 and a scan classification accuracy of 0.94. The visualizations show that our network learned better features than other networks.

SIGNIFICANCE

The proposed methods can potentially be a step towards the early diagnosis of corneal diseases, which is necessary to prevent their progression, hence, prevent loss of vision.

Pathological-Corneas Layer Segmentation and Thickness Measurement in OCT Images

Purpose

The purpose of this study was to propose a new algorithm for the segmentation and thickness measurement of pathological corneas with irregular layers using a two-stage graph search and ray tracing.

Methods

In the first stage, a graph, with only gradient edge-cost, is used to segment the air-epithelium and endothelium-aqueous boundaries. In the second stage, a graph, with gradient, directional, and multiplier edge-cost, is used to correct segmentation. The optical coherence tomography (OCT) image is flattened using the air-epithelium boundary and a graph search is used to segment the epithelium-Bowman's and Bowman's-stroma boundaries. Then, the OCT image is flattened using the endothelium-aqueous boundary and a graph search is used to segment the Descemet's membrane. Ray tracing is used to correct the inter-boundary distances, then the thickness is measured using the shortest distance. The proposed algorithm was trained and evaluated using 190 OCT images manually segmented by trained operators.

Results

The mean and standard deviation of the unsigned errors of the algorithm-operator and inter-operator were 0.89 ± 1.03 and 0.77 ± 0.68 pixels in segmentation and 3.62 ± 3.98 and 2.95 ± 2.52 µm in thickness measurement.

Conclusions

Our proposed algorithm can produce accurate segmentation and thickness measurements compared with the manual operators.

Translational Relevance

Our algorithm could be potentially useful in the clinical practice.

Automated diagnosis and staging of Fuchs' endothelial cell corneal dystrophy using deep learning

Background

To describe the diagnostic performance of a deep learning algorithm in discriminating early-stage Fuchs’ endothelial corneal dystrophy (FECD) without clinically evident corneal edema from healthy and late-stage FECD eyes using high-definition optical coherence tomography (HD-OCT).

Methods

In this observational case-control study, 104 eyes (53 FECD eyes and 51 healthy controls) received HD-OCT imaging (Envisu R2210, Bioptigen, Buffalo Grove, IL, USA) using a 6 mm radial scan pattern centered on the corneal vertex. FECD was clinically categorized into early (without corneal edema) and late-stage (with corneal edema). A total of 18,720 anterior segment optical coherence tomography (AS-OCT) images (9180 healthy; 5400 early-stage FECD; 4140 late-stage FECD) of 104 eyes (81 patients) were used to develop and validate a deep learning classification network to differentiate early-stage FECD eyes from healthy eyes and those with clinical edema. Using 5-fold cross-validation on the dataset containing 11,340 OCT images (63 eyes), the network was trained with 80% of these images (3420 healthy; 3060 early-stage FECD; 2700 late-stage FECD), then tested with 20% (720 healthy; 720 early-stage FECD; 720 late-stage FECD). Thereafter, a final model was trained with the entire dataset consisting the 11,340 images and validated with a remaining 7380 images of unseen AS-OCT scans of 41 eyes (5040 healthy; 1620 early-stage FECD 720 late-stage FECD). Visualization of learned features was done, and area under curve (AUC), specificity, and sensitivity of the prediction outputs for healthy, early and late-stage FECD were computed.

Results

The final model achieved an AUC of 0.997 ± 0.005 with 91% sensitivity and 97% specificity in detecting early-FECD; an AUC of 0.974 ± 0.005 with a specificity of 92% and a sensitivity up to 100% in detecting late-stage FECD; and an AUC of 0.998 ± 0.001 with a specificity 98% and a sensitivity of 99% in discriminating healthy corneas from all FECD.

Conclusion

Deep learning algorithm is an accurate autonomous novel diagnostic tool of FECD with very high sensitivity and specificity that can be used to grade FECD severity with high accuracy.

Corneal graft failure: an update

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

Diagnostic Performance of 3-Dimensional Thickness of the Endothelium-Descemet Complex in Fuchs' Endothelial Cell Corneal Dystrophy

PURPOSE

To describe the diagnostic accuracy of 3-dimensional (3D) endothelium-Descemet's membrane complex thickness (En-DMT) in Fuchs' endothelial corneal dystrophy (FECD) and determine its potential role as an objective index of disease severity.

DESIGN

Observational case-control study.

PARTICIPANTS

One hundred four eyes of 79 participants (64 eyes of 41 FECD patients and 40 eyes of 38 healthy controls).

METHODS

All participants received high-definition OCT imaging (Envisu R2210; Bioptigen, Buffalo Grove, IL). Fuchs' endothelial corneal dystrophy was classified clinically into early-stage (without edema) and late-stage (with edema) disease. Automatic and manual segmentation of corneal layers was performed using a custom-built segmental tomography algorithm to generate 3D maps of total corneal thickness (TCT) and En-DMT of the central 6-mm cornea. Regional En-DMT, regional TCT, and central-to-peripheral total corneal thickness ratio (CPTR) were evaluated and correlated to the clinical severity of FECD. Intraclass correlation coefficients (ICCs) and Bland-Altman plots were used to assess the reliability of the repeated measurements in all eyes.

MAIN OUTCOME MEASURES

Central-to-peripheral total corneal thickness ratio and average En-DMT and TCT of central, paracentral, and peripheral regions.

RESULTS

In FECD, a significant increase in En-DMT, CPTR_, and TCT was found compared to controls (P < 0.001). For identifying FECD, average En-DMT of paracentral and peripheral regions achieved 94% sensitivity and 100% specificity (cutoffs, 19 μm and 20 μm, respectively), whereas CPTR showed 94% sensitivity with a 73% specificity (cutoff, 0.97). Regarding early-stage FECD, average En-DMT of central zones achieved 92% sensitivity and 97% specificity (cutoff, 18 μm), whereas CPTR showed 90% sensitivity and 88% specificity (cutoff, 0.97). The average En-DMT of central, paracentral, and peripheral regions was correlated highly with FECD clinical stage (Spearman's ρ = 0.813, 0.793, and 0.721, respectively; all P < 0.001), compared with CPTR and mean TCT of paracentral zones (0.672 and 0.481, respectively; P < 0.001). The ICC values ranged from 0.98 (En-DMT) to 0.99 (TCT) with a good agreement between the automatic and manual measurements.

CONCLUSIONS

Regional 3D En-DMT is a novel diagnostic tool of FECD that can be used to quantify the disease severity with excellent reliability.

In-vivo Three-dimensional Characteristics of Bowman's Layer and Endothelium/Descemet's Complex Using Corneal Microlayer Tomography in Healthy Subjects

Purpose: To characterize the three-dimensional (3D) thickness profile and age-related changes of Bowman's layer (BL), and endothelium/Descemet's membrane (En/DM) complex among healthy individuals using Corneal Microlayer Tomography (CML-T), and to describe its repeatability and accuracy.Methods: Sixty-six eyes of 41 healthy volunteers; 27 eyes (< 40 years old), and 39 eyes (>40 years old) were imaged using HD-OCT. Automatic and manual segmentation of the corneal layers was performed, and 3D thickness maps were generated, using custom-built CML-T software. A regional analysis of mean thickness parameters between the 2 age groups was performed. A regression analysis was used to assess the correlation between age, and thickness maps. Intraclass Correlation Coefficients (ICC), Coefficients of Variation (COV), and Bland-Altman plots were used to assess the reliability of the repeated measurements in 198 locations.Results: CML-T successfully mapped the BL and En/DM in all included eyes. Thickness maps showed a significant increase in corneal thickness (CT), BL thickness (BMT), and En/DM complex thickness (DMT) toward the periphery with a mean difference 28 µm (p < .001), 1.1 µm (p < .001), and 1.4 µm (p < .001), respectively. There was a strong correlation between age and central DMT (r = 0.61; p < .001), while there was no correlation between age and both CT, and BMT. ICC values ranged from 0.9 (BMT) to 0.997 (DMT), and from 0.808 (BMT) to 0.979 (CT) for intraoperator repeatability of manual measurements, and the accuracy of auto matic measurements, respectively. COV values were lower than 7.5% in all cases.Conclusion: CML-T is a novel tool that can generate 3D-thickness maps of both BL and En/DM. CT, BMT, and DMT increase toward the periphery in healthy corneas. DMT increases with aging, while BMT does not. We also report excellent repeatability, accuracy and good agreement between automatic and manual measurements.

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.

A double masked randomised 4-week, placebo-controlled study in the USA, Thailand and Taiwan to compare the efficacy of oral valganciclovir and topical 2% ganciclovir in the treatment of cytomegalovirus anterior uveitis: study protocol

INTRODUCTION

Cytomegalovirus (CMV) anterior uveitis is a recognised cause of anterior uveitis in immunocompetent patients and is preventable cause of vision loss. Ocular sequelae include corneal endothelial damage which can cause corneal oedema and failure, as well as glaucoma. Recurrences of inflammation are common and therefore patients are often exposed to long-term therapy. Oral therapy is available in the form of valganciclovir, although with the caveat of systemic side effects such as bone marrow suppression and renal failure necessitating regular interval laboratory monitoring. Recent reports have demonstrated that topical 2% ganciclovir solution may offer promising treatment outcomes in patients with CMV anterior uveitis with superior safety, cost-effectiveness and convenience profiles. An investigation into the relative equipoise of these therapies is warranted for these reasons.

METHODS AND ANALYSIS

The Systemic and Topical Control of Cytomegalovirus Anterior uveitis: Treatment Outcomes (STACCATO) trial is designed as a multicentre, block randomised by site, double-masked, placebo-controlled trial comparing the efficacy of oral valganciclovir, 2% topical ganciclovir and placebo in treating PCR-proven CMV anterior uveitis. Participant clinical evaluation will occur at three study time points by a masked study ophthalmologist over a 28-day period to assess resolution of ocular inflammation (secondary outcome). A control group will provide additional information about the possible impact that the infected host's immune response may play in controlling local viral replication. The primary analysis is an analysis of covariance (three arms) correcting for baseline to compare quantitative CMV viral load in the anterior chamber (AC) aqueous fluid before and 7 days after treatment.

ETHICS AND DISSEMINATION

The University of California San Francisco Committee on Human Research and the Khon Kaen University Institutional Review Board have given ethical approval. The results of this trial will be presented at local and international meetings and submitted for peer-reviewed journals for publication.

TRIAL REGISTRATION NUMBER

NCT03576898.

The Use of Digital Microscopy to Compare the Thicknesses of Normal Corneas and Ex Vivo Rejected Corneal Grafts with a Focus on the Descemet's Membrane

Objective

To compare the thickness of corneal layers, specifically the Descemet's membrane (DM), in normal corneas and in failed grafts due to rejection (FGRs) using the digital histopathology and to propose a model for the measurement of corneal layers using this method.

Methods

This is a prospective, cross-sectional study performed at the MUHC-McGill University Ocular Pathology & Translational Research Laboratory (McGill University, Montreal, Canada). Histopathological sections of 25 normal human corneas and 40 FGRs were fully digitalized and examined. Inclusion criteria: samples diagnosed as normal corneas or FGRs, from patients older than 18 years of age. Exclusion criteria: histopathological sections without adequate tissue or missing epidemiological information. For each sample, the thicknesses of the epithelium, stroma, and DM were acquired. From a perpendicular plane of reference, two central measurements and two nasal and two temporal peripheral measurements were obtained.

Results

There were differences between the normal and FGR groups in the mean central thickness of the epithelium (p < 0.001), the nasal and temporal stromal regions (p < 0.001), and of the DM in the nasal and temporal regions (p < 0.001). Compared with the extremities of the sample (nasal and temporal), the mean thickness of the DM in normal corneas was lower in the central region (p < 0.001), and this difference was not found in the FGR group.

Conclusions

Normal corneas have a thinner epithelium in the central region than the FGR group. In addition, the stroma and DM thicknesses of the nasal and temporal periphery were significantly higher in normal corneas than in those from the FGR group. The digital microscopy protocol applied in this study may be useful for further research studies regarding cornea and other tissues.

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

PURPOSE

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

DESIGN

Prospective case-control study.

SUBJECTS

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

METHODS

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

MAIN OUTCOME MEASUREMENTS

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

RESULTS

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

CONCLUSIONS

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

Automatic Segmentation of Corneal Microlayers on Optical Coherence Tomography Images

Purpose

To propose automatic segmentation algorithm (AUS) for corneal microlayers on optical coherence tomography (OCT) images.

Methods

Eighty-two corneal OCT scans were obtained from 45 patients with normal and abnormal corneas. Three testing data sets totaling 75 OCT images were randomly selected. Initially, corneal epithelium and endothelium microlayers are estimated using a corneal mask and locally refined to obtain final segmentation. Flat-epithelium and flat-endothelium images are obtained and vertically projected to locate inner corneal microlayers. Inner microlayers are estimated by translating epithelium and endothelium microlayers to detected locations then refined to obtain final segmentation. Images were segmented by trained manual operators (TMOs) and by the algorithm to assess repeatability (i.e., intraoperator error), reproducibility (i.e., interoperator and segmentation errors), and running time. A random masked subjective test was conducted by corneal specialists to subjectively grade the segmentation algorithm.

Results

Compared with the TMOs, the AUS had significantly less mean intraoperator error (0.53 ± 1.80 vs. 2.32 ± 2.39 pixels; P < 0.0001), it had significantly different mean segmentation error (3.44 ± 3.46 vs. 2.93 ± 3.02 pixels; P < 0.0001), and it had significantly less running time per image (0.19 ± 0.07 vs. 193.95 ± 194.53 seconds; P < 0.0001). The AUS had insignificant subjective grading for microlayer-segmentation grading (4.94 ± 0.32 vs. 4.96 ± 0.24; P = 0.5081), but it had significant subjective grading for regional-segmentation grading (4.96 ± 0.26 vs. 4.79 ± 0.60; P = 0.025).

Conclusions

The AUS can reproduce the manual segmentation of corneal microlayers with comparable accuracy in almost real-time and with significantly better repeatability.

Translational Relevance

The AUS can be useful in clinical settings and can aid the diagnosis of corneal diseases by measuring thickness of segmented corneal microlayers.

Evaluation of endothelial/Descemet membrane complex of eye bank donor corneas using enhanced depth imaging optical coherence tomography

Objective: We present a novel method for screening eye bank donor corneas using high definition optical coherence tomography (HD-OCT). This technology allows for the quantification of endothelial/Descemet membrane (En/DM) complex thickness ex vivo.

Design: Prospective interventional study.

Participants: Fifty-two corneal grafts from 27 donors were included in this study. Twenty additional control eyes and 11 eyes with Fuchs’ endothelial corneal dystrophy were also evaluated for comparison.

Methods: A custom built, high speed HD-OCT device (Envisu R2210, Bioptigen, Buffalo Grove, IL, USA) was used to obtain images, and custom-made graph-based segmentation software was used to automatically deconstruct corneal images into micro-layers. HD-OCT imaging was used to scan through the sealed sterile case of donor corneas stored in McCarey-Kaufman medium to image their En/DM complex through the center of the cornea.

Results: This technology allowed for quantification of En/DM complex thickness in all donor corneas through the sealed sterile container used to transport graft tissue. Mean En/DM complex thickness of donor corneas was 17±4 μm. The difference between donor cornea En/DM thickness and that of control subjects (16±2 μm) was not statistically significant (p=0.3), suggesting that the transport container and media do not affect measurements. There was a significant difference between En/DM thickness of Fuchs’ endothelial corneal dystrophy eyes (25±5 μm) and both donor corneas (p<0.0001) and control subjects (p<0.0001).

Conclusions: We have described a new technique to measure En/DM complex thickness in eye bank donor corneas stored in a sealed sterile case. This may represent a novel adjunctive approach to screen corneal grafts for early endothelial disease.

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.

Descemet Membrane Thickening as a Sign for the Diagnosis of Corneal Graft Rejection: An Ex Vivo Study

PURPOSE

To disclose, using an ex vivo study, the histopathological mechanism behind in vivo thickening of the endothelium/Descemet membrane complex (En/DM) observed in rejected corneal grafts (RCGs).

METHODS

Descemet membrane (DM), endothelium, and retrocorneal membranes make up the total En/DM thickness. These layers are not differentiable by high-definition optical coherence tomography; therefore, the source of thickening is unclear from an in vivo perspective. A retrospective ex vivo study (from September 2015 to December 2015) was conducted to measure the thicknesses of DM, endothelium, and retrocorneal membrane in 54 corneal specimens (31 RCGs and 23 controls) using light microscopy. Controls were globes with posterior melanoma without corneal involvement.

RESULTS

There were 54 corneas examined ex vivo with mean age 58.1 ± 12.2 in controls and 51.7 ± 27.9 years in RCGs. The ex vivo study uncovered the histopathological mechanism of En/DM thickening to be secondary to significant thickening (P < 0.001) of DM (6.5 ± 2.4 μm) in RCGs compared with controls (3.9 ± 1.5 μm).

CONCLUSIONS

Our ex vivo study shows that DM is responsible for thickening of the En/DM in RCGs observed in vivo by high-definition optical coherence tomography and not the endothelium or retrocorneal membrane.