Predicting the Prognosis of Fuchs Endothelial Corneal Dystrophy by Using Scheimpflug Tomography

Assessing Fuchs Corneal Endothelial Dystrophy Using Artificial Intelligence-Derived Morphometric Parameters From Specular Microscopy Images

PURPOSE

The aim of this study was to evaluate the efficacy of artificial intelligence-derived morphometric parameters in characterizing Fuchs corneal endothelial dystrophy (FECD) from specular microscopy images.

METHODS

This cross-sectional study recruited patients diagnosed with FECD, who underwent ophthalmologic evaluations, including slit-lamp examinations and corneal endothelial assessments using specular microscopy. The modified Krachmer grading scale was used for clinical FECD classification. The images were processed using a convolutional neural network for segmentation and morphometric parameter estimation, including effective endothelial cell density, guttae area ratio, coefficient of variation of size, and hexagonality. A mixed-effects model was used to assess relationships between the FECD clinical classification and measured parameters.

RESULTS

Of 52 patients (104 eyes) recruited, 76 eyes were analyzed because of the exclusion of 26 eyes for poor quality retroillumination photographs. The study revealed significant discrepancies between artificial intelligence-based and built-in microscope software cell density measurements (1322 ± 489 cells/mm 2 vs. 2216 ± 509 cells/mm 2 , P < 0.001). In the central region, guttae area ratio showed the strongest correlation with modified Krachmer grades (0.60, P < 0.001). In peripheral areas, only guttae area ratio in the inferior region exhibited a marginally significant positive correlation (0.29, P < 0.05).

CONCLUSIONS

This study confirms the utility of CNNs for precise FECD evaluation through specular microscopy. Guttae area ratio emerges as a compelling morphometric parameter aligning closely with modified Krachmer clinical grading. These findings set the stage for future large-scale studies, with potential applications in the assessment of irreversible corneal edema risk after phacoemulsification in FECD patients, as well as in monitoring novel FECD therapies.

Scheimpflug Corneal Tomography Anterior Chamber Depth in Descemet Stripping Endothelial Keratoplasty Recipients

PURPOSE

Our study investigates whether preoperative anterior chamber depth (ACD) measured by Scheimpflug tomography could serve as a potential predictor of graft failure in eyes undergoing Descemet stripping endothelial keratoplasty (DSEK).

METHODS

A retrospective review was conducted on patients who underwent primary or repeat DSEK between January 2020 and August 2021 at Bascom Palmer Eye Institute. Charts from 378 primary and 192 repeat DSEK patients were reviewed and ultimately 47 primary and 21 repeat DSEK patients met criteria for inclusion. Data collection included demographics, preoperative ACD, best-corrected visual acuity, and length of follow-up.

RESULTS

Demographics were similar between groups, and there was no significant difference in the average best-corrected visual acuity between the single and repeat DSEK groups preoperatively. Baseline preoperative ACD was greatest in the single DSEK group (3.51 ± 0.90 mm) when compared to baseline preoperative ACD in the repeat DSEK group (3.01 ± 0.67 mm, P = 0.003). The preoperative mean ACD was smallest in the repeat DSEK group before the second DSEK (2.94 ± 0.48 mm, P = 0.001). Preoperative baseline ACD was the only variable to affect graft survival time significantly ( P = 0.012). The incidence of glaucoma diagnosis was similar in both groups (42.5% vs. 42.8%, P = 0.471). The diagnosis of glaucoma and presence of incisional glaucoma surgery did not affect the graft survival time ( P = 0.129, P = 0.559) or need for repeat DSEK.

CONCLUSIONS

Smaller baseline preoperative Scheimpflug ACD measurement may be a possible predictor of the need for repeat DSEK. Our study found that Scheimpflug ACD decreases with subsequent DSEK failure.

Scheimpflug Tomography as a Predictor of Corneal Edema After Phacoemulsification in Fuchs Endothelial Corneal Dystrophy

Purpose

To determine if Scheimpflug tomography pachymetry map and posterior elevation map patterns can predict the occurrence of corneal edema following uneventful phacoemulsification surgery in Fuchs endothelial corneal dystrophy (FECD).

Design

Observational prospective case-control study.

Participants

Fifty FECD eyes (50 patients) with visually significant cataract: 25 with subclinical corneal edema (SCE) versus 25 without SCE.

Methods

Preoperatively, FECD was clinically assessed, and only patients devoid of clinical corneal edema were enrolled. Utilizing the Mayo Clinic classification for subclinical corneal edema (SCE), eligible FECD eyes were stratified based on Scheimpflug imaging pachymetry map and posterior elevation map characteristics, including loss of regular isopachs, displacement of the cornea's thinnest point, and the presence of posterior surface depression, into two groups: Group A representing FECD with SCE, and Group B: FECD without SCE. One week postoperatively, clinical and tomographic evaluation was performed. Regression analysis was conducted to evaluate predictors of corneal edema after uneventful phacoemulsification surgery in both groups.

Results

All patients were successfully imaged before and 1 week after surgery. Visual acuity was significantly improved in both groups (P < 0.001). No postoperative clinical edema was observed in Group B, while 23 (92%) had mild edema and 2 (8%) had moderate edema in Group A. Both groups showed a significant increase in postoperative central corneal thickness (CCT) and thinnest corneal thickness (TCT) (both P < 0.001). Compared to Group B, Group A showed a significant central flattening of the anterior corneal surface (P = 0.007 and P = 0.04 for K1 and K2 respectively), and a significant increase in the postoperative posterior surface depression. Multivariate analysis showed that 94% of postoperative corneal edema could be predicted by the presence of preoperative posterior surface depression (P = 0.04, ARR = 5.8 (1.89-35.7)).

Conclusion

Scheimpflug tomography pachymetry map and posterior elevation map patterns can predict corneal edema after uneventful phacoemulsification surgery in FECD with subclinical corneal edema.

Change in Visual Acuity of Patients With Fuchs Endothelial Corneal Dystrophy Over 1 Year

PURPOSE

To determine whether the clinical and paraclinical course of Fuchs endothelial corneal dystrophy (FECD) over 1 year is related to the extent of triplet repetition in the transcription factor 4 (TCF4) gene.

METHODS

A prospective study with a 1-year follow-up was conducted. A total of 104 patients (160 eyes) with FECD and an equivalent number of age- and sex-matched control subjects without FECD were included. At inclusion, the corneas were graded using the modified Krachmer grade (KG) and patients were genotyped for the number of trinucleotide repeats (TNRs) in the TCF4 gene by the short tandem repeat assay. Visual acuity, Scheimpflug tomographic features, and the Visual Function and Corneal Health Status using a visual disability instrument were measured on 2 visits at 1-year intervals.

RESULTS

KGs ranged from 1 to 6, and 46% of eyes had grades 1 to 4. 71% of the patients harbored TNR expansion (>40) versus 13% in control subjects (P < 0.001). Severity at inclusion was higher in the presence of TNR expansion when considering eyes independently (mean grade ±SD, 4.08 ± 1.42) without TNR expansion and 4.66 ± 1.27 with TNR expansion (P = 0.024). In 1 year, the ETDRS score significantly decreased by -2.97 (95% confidence interval -4.69 to -1.26, P = 0.001) and the ETDRS score with glare by -4.25 (95% confidence interval -6.22 to -2.27, P < 10-5). There was no relationship between the rate of decline and TNR expansion or KG. Central corneal thickness and Visual Function and Corneal Health Status scores did not significantly vary.

CONCLUSIONS

It is possible to measure a subtle progression of FECD over a period as short as 1 year. We did not find a relationship between the presence of TNR expansion and the speed of deterioration over 1 year. This work should facilitate the design of future clinical trials on FECD.Trial Registration-URL: ClinicalTrials.gov. Identifier: French Fuchs Follow-up Study (F3S): NCT03974230.

Corneal Backscatter, Pachymetric Indices, and Ectasia Indices for the Assessment of Fuchs Endothelial Corneal Dystrophy

PURPOSE

To determine whether corneal backscatter, pachymetric indices, and ectasia indices derived from Scheimpflug tomography can identify Fuchs endothelial corneal dystrophy (FECD) corneas with abnormal tomography, the relationships between these parameters and tomographic edema in FECD, and if these parameters help predict improvement in central corneal thickness (CCT) after Descemet membrane endothelial keratoplasty (DMEK).

METHODS

Tomography maps of 132 eyes of 80 subjects with FECD were analyzed to determine how backscatter, pachymetric, and ectasia parameters compared with the instrument's normative database and if any predicted tomographic edema. Tomography maps from a separate group undergoing DMEK were split into derivation (48 eyes of 39 subjects) and validation (45 eyes of 41 subjects) subgroups to derive a predictive model of improvement in CCT after DMEK. Backscatter, pachymetric, and ectasia parameters were incorporated to determine if the model could be enhanced.

RESULTS

Among all ectasia, pachymetric, and backscatter parameters, at best only 65% of FECD corneas with definite tomographic edema could be identified based on the instrument's normative database. Among all parameters individually, the highest sensitivity for detecting tomographic edema was 77%. Anterior and mid-corneal backscatter featured in a model predicting improvement in CCT after DMEK with high performance in derivation (R2 = 0.79; 95% confidence interval, 0.65-0.87) and validation (R2 = 0.72; 95% confidence interval, 0.52-0.83) subgroups.

CONCLUSIONS

The Scheimpflug camera software program could not reliably detect abnormal tomography in FECD from corneal backscatter, pachymetric indices, or ectasia indices. Corneal backscatter contributes to, but does not enhance, a predictive model of improvement in CCT after DMEK.

A multi-ancestry GWAS of Fuchs corneal dystrophy highlights the contributions of laminins, collagen, and endothelial cell regulation

Fuchs endothelial corneal dystrophy (FECD) is a leading indication for corneal transplantation, but its molecular etiology remains poorly understood. We performed genome-wide association studies (GWAS) of FECD in the Million Veteran Program followed by multi-ancestry meta-analysis with the previous largest FECD GWAS, for a total of 3970 cases and 333,794 controls. We confirm the previous four loci, and identify eight novel loci: SSBP3, THSD7A, LAMB1, PIDD1, RORA, HS3ST3B1, LAMA5, and COL18A1. We further confirm the TCF4 locus in GWAS for admixed African and Hispanic/Latino ancestries and show an enrichment of European-ancestry haplotypes at TCF4 in FECD cases. Among the novel associations are low frequency missense variants in laminin genes LAMA5 and LAMB1 which, together with previously reported LAMC1, form laminin-511 (LM511). AlphaFold 2 protein modeling, validated through homology, suggests that mutations at LAMA5 and LAMB1 may destabilize LM511 by altering inter-domain interactions or extracellular matrix binding. Finally, phenome-wide association scans and colocalization analyses suggest that the TCF4 CTG18.1 trinucleotide repeat expansion leads to dysregulation of ion transport in the corneal endothelium and has pleiotropic effects on renal function.

Characterisation of ectasia after penetrating keratoplasty in keratoconus eyes using anterior segment optical coherence tomography

BACKGROUND/AIMS

Ectasia of the cornea can occur decades after penetrating keratoplasty (PK), especially in keratoconus eyes. The purpose of this study was to characterise ectasia after PK by morphological findings in anterior segment optical coherence tomography (AS-OCT).

METHODS

In this retrospective, single-centre case series, 50 eyes of 32 patients with a history of PK at an average of 25±10 years earlier were included. The eyes were classified either as ectatic (n=35) or as non-ectatic (n=15). The main parameters included central corneal thickness (CCT), lowest corneal thickness at the interface (LCTI), anterior chamber depth, graft-host interface angle at the thinnest point and host cornea-iris angle. Furthermore, steep and flat keratometry readings obtained by AS-OCT (CASIA-2, Tomey) and Scheimpflug tomography (Pentacam, Oculus) were assessed. OCT findings were correlated with clinical grading of ectasia.

RESULTS

There was a highly significant difference in LCTI, graft-host interface angle and anterior chamber depth (in pseudophakic eyes) between the groups. The ratio calculated by the quotient of LCTI divided by CCT was significantly lower in ectatic than non-ectatic eyes (p<0.001). In eyes with an LCTI/CCT ratio of ≤0.7, the OR for the occurrence of a clinical detectable ectasia was 2.4 (CI 1.5 to 3.7). Steep keratometry values were significantly higher in ectatic eyes.

CONCLUSION

AS-OCT is a helpful tool to recognise and quantify ectasia in post-PK eyes objectively.

Applications of Imaging Technologies in Fuchs Endothelial Corneal Dystrophy: A Narrative Literature Review

Fuchs endothelial corneal dystrophy (FECD) is a complex genetic disorder characterized by the slow and progressive degeneration of corneal endothelial cells. Thus, it may result in corneal endothelial decompensation and irreversible corneal edema. Moreover, FECD is associated with alterations in all corneal layers, such as thickening of the Descemet membrane, stromal scarring, subepithelial fibrosis, and the formation of epithelial bullae. Hence, anterior segment imaging devices that enable precise measurement of functional and anatomical changes in the cornea are essential for the management of FECD. In this review, the authors will introduce studies on the application of various imaging modalities, such as anterior segment optical coherence tomography, Scheimpflug corneal tomography, specular microscopy, in vitro confocal microscopy, and retroillumination photography, in the diagnosis and monitoring of FECD and discuss the results of these studies. The application of novel technologies, including image processing technology and artificial intelligence, that are expected to further enhance the accuracy, precision, and speed of the imaging technologies will also be discussed.

Comparative Analysis of Tomographic Indicators Forecasting Decompensation in Fuchs Endothelial Corneal Dystrophy

PURPOSE

To compare the performance of 3 commercially available tomographers (the Pentacam Scheimpflug camera, the swept-source optical coherence tomography Casia, and the blue light slit-scanning tomographer Precisio) in the identification of patterns associated with Fuchs endothelial corneal dystrophy (FECD) decompensation.

METHODS

This was a clinic-based cross-sectional imaging study. Pachymetry maps and posterior surface elevation maps were acquired with the 3 devices from 61 eyes affected by FECD. The maps were graded according to the evidence of tomographic patterns predictive of FECD decompensation (loss of parallel isopachs, displacement of the thinnest point, and focal posterior depression) by 2 blind cornea specialists.

RESULTS

The loss of parallel isopachs was significantly less frequently evident in Pentacam pachymetry maps [8%, 95% confidence interval (CI) (3%, 18%)] compared with both the Casia [31%, 95% CI (20%, 44%), P = 0.01] and Precisio devices [24%, 95% CI (15%, 37%), P = 0.05]. The displacement of the thinnest point was graded as most evident in a significantly higher proportion of Precisio pachymetry maps [43%, 95% CI (31%, 55%)] compared with both the Pentacam [13%, 95% CI (6%, 24%), P = 0.001] and Casia devices [21%, 95% CI (12%, 33%), P = 0.03]. There were no significant differences in the identification of focal posterior depression on posterior elevation maps across the 3 devices.

CONCLUSIONS

Identification of patterns predictive of FECD prognosis on pachymetry and posterior elevation maps is possible with different devices. However, their evidence varies across tomographers, and the results from different devices are not interchangeable.

Differences in Guttae Ultramorphology in Relation to Visual Function in Fuchs Endothelial Corneal Dystrophy

PURPOSE

The purpose of this study was to investigate the differences in guttae ultramorphology and their relation to visual function in eyes with Fuchs endothelial corneal dystrophy (FECD).

METHODS

Thirty FECD eyes without ocular comorbidities were included. Visual functional parameters (best-corrected visual acuity with high-contrast and low-contrast letters and contrast sensitivity/LogCS) and corneal morphology measured with Scheimpflug tomography (Pentacam) were assessed. The surgically removed Descemet membranes were examined by light and transmission electron microscopy.

RESULTS

Preoperative mean best-corrected visual acuity (logarithm of the minimum angle of resolution) was 0.52 ± 0.18, LogCS 0.96 ± 0.21 and central corneal thickness 640 ± 55 μm. All eyes had signs of subclinical corneal edema in Scheimpflug tomography; clinically visible corneal edema was present in 40% of eyes. Histological findings included a posterior fibrillar zone (PFZ) in 10 specimens (33%) and abnormal collagen depositions in Descemet membranes in 14 specimens (47%). Guttae buried within the PFZ were present only in eyes with clinically visible edema (n = 4, 13%). There was no difference in visual function results and tomography parameters between eyes with and without PFZ or between protruding guttae and guttae embedded in a PFZ, respectively.

CONCLUSIONS

Guttae morphology and density were not correlated with visual functional parameters. Guttae buried in a PFZ occurred only in eyes with clinically manifest edema, and thereby, they are an ultramorphological sign for advanced FECD. Subclinical edema was present in all eyes and might be more relevant for quality of vision than guttae ultramorphology.

Translation and validation of the Visual Function and Corneal Health Status (V-FUCHS) questionnaire into Spanish language

PURPOSE

To translate and validate the V-FUCHS questionnaire into Spanish in a population of patients with Fuchs endothelial dystrophy (DEF).

METHODS

The V-FUCHS consists of 15 short, easily understandable questions that assess visual aspects of quality of life in patients with DEF, which can be gathered into a group of seven that assess the "Visual Difficulty" factor and another group of eight that assess the "Glare Factor". For the translation and cultural adaptation, the standardized norms for this process were followed, among other phases, a translation, a back-translation and an application in patients with DEF.

RESULTS

In the first phase, consensus was reached on the Spanish translation of the V-FUCHS. Subsequently, 25 patients were included to carry out the pre-test phase with the aim of assessing the applicability and feasibility of the test. The score obtained a minimum value of -0.88 and a maximum value of +2.44, according to the Rasch probabilistic scale. The mean value obtained from the Visual Difficulty factor was 0.61 (±0.71), while the mean for the Glare Factor was 0.41 (±0.51).

CONCLUSION

The validation of the V-FUCHS questionnaire, after its translation and adaptation into Spanish, proved to be a useful tool for assessing the visual quality of patients with DEF. Patients with a more advanced stage of the disease presented a greater severity in the test result. Likewise, the Glare Factor (Glare) correlates better with the pachymetric increase than with the visual acuity of the patient.

Systematic Review of the Diagnostic Criteria and Severity Classification for Fuchs Endothelial Corneal Dystrophy

PURPOSE

There are no defined diagnostic criteria and severity classification for Fuchs endothelial corneal dystrophy (FECD), which are required for objective standardized assessments. Therefore, we performed a systematic literature review of the current diagnosis and severity classification of FECD.

METHODS

We searched the Ovid MEDLINE and Web of Science databases for studies published until January 13, 2021. We excluded review articles, conference abstracts, editorials, case reports with <5 patients, and letters.

RESULTS

Among 468 articles identified, we excluded 173 and 165 articles in the first and second screenings, respectively. Among the 130 included articles, 61 (47%) and 99 (76%) mentioned the diagnostic criteria for FECD and described its severity classification, respectively. Regarding diagnosis, slitlamp microscope alone was the most frequently used device in 31 (51%) of 61 articles. Regarding diagnostic findings, corneal guttae alone was the most common parameter [adopted in 23 articles (38%)]. Regarding severity classification, slitlamp microscopes were used in 88 articles (89%). The original or modified Krachmer grading scale was used in 77 articles (78%), followed by Adami's classification in six (6%). Specular microscopes or Scheimpflug tomography were used in four articles (4%) and anterior segment optical coherence tomography in one (1%).

CONCLUSIONS

FECD is globally diagnosed by the corneal guttae using slitlamp examination, and its severity is predominantly determined by the original or modified Krachmer grading scale. Objective severity grading using Scheimpflug or anterior segment optical coherence tomography can be applied in the future innovative therapies such as cell injection therapy or novel small molecules.

Descemet Stripping Automated Endothelial Keratoplasty versus Descemet Membrane Endothelial Keratoplasty for Fuchs Endothelial Corneal Dystrophy: A National Registry-Based Comparison

PURPOSE

To compare the outcome between posterior lamellar corneal transplant procedures for Fuchs endothelial corneal dystrophy, taking preoperative patient characteristics in consideration. Surgical methods compared were Descemet membrane endothelial keratoplasty (DMEK), Descemet stripping automated endothelial keratoplasty (DSAEK), and DSAEK with concomitant cataract surgery (phacoemulsification plus DSAEK).

DESIGN

Registry-based study with propensity score matching.

PARTICIPANTS

One thousand six hundred seventy-seven patients from all Swedish corneal transplantation units treated from 2012 through 2019.

METHODS

All patients undergoing endothelial keratoplasty performed from 2012 through 2019 with completed 2-year follow-up data reported to The Swedish Corneal Transplant Register were included, totaling 1677 patients. Three comparable groups (DMEK, DSAEK, and phacoemulsification plus DSAEK) with 216 patients in each group were generated with propensity score matching based on preoperative visual acuity, age, sex, year of surgery, and preoperative risk factors such as inflammation, vascularization, and glaucoma.

MAIN OUTCOME MEASURES

Best-corrected visual acuity (BCVA) at the 2-year follow-up, frequency of graft dislocation, graft rejection episodes, and graft failure within 2 years including primary graft failure.

RESULTS

The preoperative corneal status was affected more severely in the DSAEK group before matching. In the matched groups, the median BCVA 2 years after surgery was 0.1 logarithm of the minimum angle of resolution (logMAR) in both the DMEK and the phacoemulsification plus DSAEK groups and 0.15 logMAR in the DSAEK group (P = 0.001). The frequency of graft dislocation was higher among the patients undergoing phacoemulsification plus DSAEK, but the frequency of graft failure and primary graft failure was higher in the DMEK group.

CONCLUSIONS

Visual acuity improved in most patients (90%) with all 3 surgical methods. However, DMEK and phacoemulsification plus DSAEK reached higher levels of visual acuity 2 years after surgery, and phacoemulsification plus DSAEK was superior considering graft survival rate. All 3 surgical procedures showed both strengths and weaknesses, suggesting that the choice of surgical method should be individualized, taking into consideration not only the cornea, but each patient's complete medical status as well as the entire course of postoperative medical care.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Descemet membrane endothelial keratoplasty combined with presbyopia-correcting and toric intraocular lenses - a narrative review

Fuchs endothelial corneal dystrophy (FECD) is the leading indication for EK and may coexist with cataract and presbyopia. Notably, the outcomes of phacoemulsification in FECD patients are not as favorable as those in eyes without this condition. Historically, only monofocal intraocular lenses (IOLs) were recommended for these patients. However, recent reports have described the implantation of Premium-IOLs (such as Multifocal IOLs, Enhanced Depth of Focus IOLs, and Toric IOLs) in FECD eyes undergoing cataract surgery and Descemet membrane endothelial keratoplasty (DMEK). While the results are encouraging, they are not as optimal as those from unoperated eyes, especially when comparing simultaneous procedures to sequential ones. It's advised to perform the DMEK first to improve the accuracy of IOL calculations. Still, even successfully operated eyes may experience secondary graft failure or graft rejection after DMEK. The success rate of a secondary DMEK is typically lower than that of the initial procedure. Furthermore, if the postoperative thickness after DMEK is less than anticipated, laser enhancements might not be an option. There's a pressing need for more controlled and randomized clinical trials to ascertain the safety and effectiveness of Premium-IOLs for FECD eyes. This narrative review aims to collate evidence on the use of Premium IOL technologies in eyes receiving EK and to underscore key points for surgeons performing EK combined with cataract surgery.

Impact of Fuchs Endothelial Corneal Dystrophy Severity on Scheimpflug-Derived Parameters After Descemet Membrane Endothelial Keratoplasty

PURPOSE

The aim of this study was to evaluate how Scheimpflug-derived parameters of eyes with Fuchs endothelial corneal dystrophy (FECD) are influenced by Descemet membrane endothelial keratoplasty (DMEK) depending on FECD severity and the presence of subclinical edema.

METHODS

A retrospective cohort study including 115 eyes (115 patients) that underwent DMEK for FECD and a control group of 27 eyes with nonpathological corneas was conducted. Preoperative and 6 months postoperative Scheimpflug imaging was used to analyze pachymetry, presence of tomographic features (loss of isopachs/displacement of the thinnest point/focal posterior depression), and corneal backscatter. FECD severity was based on the modified Krachmer scale and the absence/presence of subclinical edema.

RESULTS

Scheimpflug-derived pachymetry, tomographic, and corneal backscatter parameters were correlated with FECD severity, and all changed from preoperatively to postoperatively (all P < 0.05). Postoperative central corneal thickness, anterior and posterior corneal backscatter, and presence of focal posterior depression remained different from the control group (all P < 0.05). Of eyes without preoperative clinical edema (n = 75), 18.7% showed 0 or 1 tomographic feature (no edema group) and 82.4% had 2 or 3 features (subclinical edema group). Compared with the control group, postoperative best-corrected visual acuity for the "no edema" group did not differ (0.03 ± 0.12 vs. -0.02 ± 0.08 logarithm of the minimum angle of resolution, P = 0.150) but was worse for the subclinical edema group (0.06 ± 0.08 vs. -0.02 ± 0.08 logarithm of the minimum angle of resolution, P = 0.001).

CONCLUSIONS

For eyes without preoperative edema, more parameters reversed back to 'normal' levels than for eyes with (sub)clinical edema. Although most analyzed parameters correlated with FECD severity, corneal tomography might be best suited for objective grading of disease severity to aid in surgical decision-making.

Fuchs Dystrophy and Cataract: Diagnosis, Evaluation and Treatment

Corneal endothelium plays an important role in maintaining hydration homeostasis and clarity of the cornea. Fuchs endothelial corneal dystrophy (FECD) affects the corneal endothelium resulting in edema and characteristic excrescences on the Descemet's membrane known as corneal guttae. Descemet membrane endothelial keratoplasty (DMEK) has evolved to become the standard of care for patients with FECD with excellent visual acuity outcomes. Patients with FECD may have coexisting cataracts and therefore may require a cataract surgery, which increases the risk of corneal decompensation. The presence of FECD may not only influence the choice of intraocular lens but vision outcomes can also be affected by the corneal condition. The ability to combine the surgeries further raises important considerations regarding the timing and sequence of DMEK and cataract extraction for patients with FECD. This review provides a guide for corneal surgeons in choosing between endothelial keratoplasty and cataract surgery-alone, in combination or sequential-in their management of patients with FECD.

Anterior Corneal High-order Aberrations in Fuchs' Endothelial Corneal Dystrophy Classified by Scheimpflug Tomography

SIGNIFICANCE

Visual acuity may be limited after endothelial keratoplasty in Fuchs' endothelial corneal dystrophy. This may be due to increased anterior high-order aberrations that persist after endothelial keratoplasty. It is not clear at what stage these aberrations begin. We aimed to evaluate how subclinical corneal edema affects anterior corneal high-order aberrations.

PURPOSE

We aimed to evaluate anterior corneal high-order aberrations according to the presence of subclinical corneal edema in Fuchs' endothelial corneal dystrophy using Scheimpflug topography.

METHODS

All the patients underwent corneal topography (Sirius Scheimpflug-Placido disc camera; CSO Ophthalmic, Scandicci, Italy). Fifty-two eyes of 31 patients with Fuchs' endothelial corneal dystrophy and 52 eyes of 35 patients without corneal problems were included. In addition, patients with Fuchs' endothelial corneal dystrophy were divided into two groups according to subclinical corneal edema as with Fuchs' endothelial corneal dystrophy-edema and Fuchs' endothelial corneal dystrophy-nonedema. Subclinical corneal edema was defined based on the presence of at least two of three findings of the loss of regular isopachs, displacement of the thinnest point of the cornea, and posterior depression. High-order aberrations were expressed as Zernike polynomials in the 4- and 6-mm optical zone.

RESULTS

We found that subclinical corneal edema in Fuchs' endothelial corneal dystrophy caused a larger 4-mm trefoil II and a smaller 6-mm spherical aberration II measurements than the nonedema group. The 6-mm total high-order aberrations, 6-mm coma aberration, and 4- and 6-mm trefoil II aberration measurements were larger, and the 6-mm spherical aberration II was smaller in Fuchs' endothelial corneal dystrophy patients with edema compared with the healthy eyes.

CONCLUSIONS

The presence of subclinical corneal edema in Fuchs' endothelial corneal dystrophy results in larger 4-mm trefoil II and smaller 6-mm spherical aberration II measurements. More patients with intermediate values are needed to evaluate the effect of these aberrations on visual acuity.

Detecting Subclinical Corneal Edema Using Corneal Thickness Mapping in Patients Presenting Fuchs Endothelial Corneal Dystrophy

PURPOSE

To determine whether local corneal thickness changes observed with optical coherence tomography (OCT) can detect subclinical corneal edema in Fuchs endothelial corneal dystrophy (FECD).

SETTING

Retrospective cohort study.

METHODS

A series of patients presenting FECD who underwent cataract surgery alone (45 eyes) or with concomitant Descemet membrane endothelial keratoplasty (triple procedure; 117 eyes). The study reviewed medical records, collected the preoperative corneal thickness map and calculated the differences and ratio of corneal thickness measured at 5, 7, and 9 mm from the central corneal thickness. Area under the receiver operating characteristic curves (AUCs) were calculated and thresholds were selected to obtain a specificity of 90%.

RESULTS

The median difference between 5- and 2-mm corneal thickness in the supra-nasal quadrant (∆5-2mmSN) was 38 µm (interquartile range 34-46) in the cataract group and 17 µm (2-38) in the triple procedure group (P < .001). The corneal thickness ratios of supra-nasal 5- to 2-mm (R5/2mmSN) and 7- to 2-mm (R7/2mmSN) were 1.07 (1.06-1.08) and 1.15 (1.13-1.17)] in the cataract group and 1.03 (1.00-1.06) and 1.09 (1.06-1.14) in the triple procedure group (P < .001). The probability of corneal edema was increased 7-fold with ∆5-2mm SN < 27 µm (AUC = 0.76) and 9.4- and 7.4-fold with R5/2mmSN and R7/2mmSN < 1.045 (AUC = 0.77) and 1.118 (AUC = 0.76), respectively.

CONCLUSIONS

Local changes in corneal thickness may be useful in detecting preclinical corneal edema, especially in patients with FECD undergoing cataract surgery.

Deep Learning Model for the Detection of Corneal Edema Before Descemet Membrane Endothelial Keratoplasty on Optical Coherence Tomography Images

Purpose

Descemet membrane endothelial keratoplasty (DMEK) is the preferred method for treating corneal endothelial dysfunction, such as Fuchs endothelial corneal dystrophy (FECD). The surgical indication is based on the patients' symptoms and the presence of corneal edema. We developed an automated tool based on deep learning to detect edema in corneal optical coherence tomography images. This study aimed to evaluate this approach in edema detection before Descemet membrane endothelial keratoplasty surgery, for patients with or without FECD.

Methods

We used our previously described model allowing to classify each pixel in the corneal optical coherence tomography images as "normal" or "edema." We included 1992 images of normal and preoperative edematous corneas. We calculated the edema fraction (EF), defined as the ratio between the number of pixels labeled as "edema," and those representing the cornea for each patient. Differential central corneal thickness (DCCT), defined as the difference in central corneal thickness before and 6 months after surgery, was used to quantify preoperative edema. AUC of EF for the edema detection was calculated for Several DCCT thresholds and a value of 20 µm was selected to define significant edema as it provided the highest area under the curve value.

Results

The area under the curve of the receiver operating characteristic curve for EF for the detection of 20 µm of DCCT was 0.97 for all patients, 0.96 for Fuchs and normal only and 0.99 for non-FECD and normal patients. The optimal EF threshold was 0.143 for all patients and patients with FECD.

Conclusions

Our model is capable of objectively detecting minimal corneal edema before Descemet membrane endothelial keratoplasty surgery.

Translational Relevance

Deep learning can help to interpret optical coherence tomography scans and aid the surgeon in decision-making.

Scheimpflug Versus Optical Coherence Tomography to Detect Subclinical Corneal Edema in Fuchs Endothelial Corneal Dystrophy

PURPOSE

The purpose of this research was to compare the ability of Scheimpflug and anterior segment optical coherence tomography (OCT) in detecting subclinical corneal edema in patients with Fuchs endothelial corneal dystrophy (FECD) without clinical corneal edema.

METHODS

In this single-center, consecutive case series, 47 eyes of 29 patients with FECD were analyzed. The main outcome measures were anterior/posterior keratometry and central/thinnest corneal thickness. The criteria for subclinical corneal edema were loss of regular isopachs, displacement of the thinnest point of the cornea, and presence of posterior surface depression. Tomographic analyses were performed using Scheimpflug imaging (Pentacam HR) and OCT (anterior segment swept-source optical coherence tomography).

RESULTS

The measurement of the continuous variables revealed a significant difference between the 2 devices. The anterior curvature was steeper and the posterior curvature was flatter when measured with OCT ( P < 0.001). The OCT showed a lower central corneal thickness and thinnest corneal thickness ( P < 0.001). The agreement between both devices to detect subclinical corneal edema was high. The interdevice reliability for loss of parallel isopachs as measured by Cohen kappa coefficient was 0.84; for the displacement of the thinnest point of the cornea, it was 0.6, and for the focal posterior corneal surface depression, it was 0.62. Subclinical corneal edema was detected in 72.3% of the patients with both devices. In only 2 cases (4.3%), subclinical corneal edema was detected by one of the devices.

CONCLUSIONS

Scheimpflug and OCT imaging were both able to detect tomographic patterns of subclinical corneal edema. Therefore, both devices can help decision-making, favoring early endothelial keratoplasty in symptomatic patients with FECD without clinical corneal edema.

Visual Function in Pseudophakic Eyes with Fuchs' Endothelial Corneal Dystrophy

PURPOSE

To assess vision in pseudophakic eyes with Fuchs' endothelial corneal dystrophy (FECD) before the onset of clinically detectable corneal edema.

DESIGN

Cross-sectional study.

METHODS

Sixty-one otherwise healthy pseudophakic eyes of 38 subjects with FECD (without clinically detectable edema) and 17 otherwise healthy pseudophakic eyes of 9 subjects with normal corneas. Subjects underwent clinical examination to determine the morphologic distribution of guttae (severity grading). Standardized best-corrected high-contract and low-contrast (photopic and mesopic) visual acuity (HCVA, LCVA) and straylight were measured. Scheimpflug tomography posterior elevation and pachymetry maps were interpreted for 3 tomographic features of subclinical edema: loss of regular isopachs, displacement of the thinnest point of the cornea, and presence of posterior surface depression.

RESULTS

In FECD without tomographic features of edema (ie, normal tomography patterns), HCVA, LCVA, and straylight did not differ from that of eyes with normal corneas (P ≥ .09); these eyes encompassed the full range of severity grading of guttae. In FECD with all 3 tomographic features of edema, the same parameters were worse compared with eyes with normal corneas (P ≤ .02). In FECD with 1 or 2 tomographic abnormalities, mesopic LCVA (P = .04) and straylight (P = .003) were worse compared with eyes with normal corneas.

CONCLUSIONS

Impairment of vision was associated with the presence of tomographic edema in eyes with FECD. When tomography patterns were normal in FECD (ie, guttae were present without tomographic edema), visual acuity and straylight were normal, and therefore corneal surgical intervention would not typically be indicated to improve vision.

Predicting Corneal Improvement after Descemet Membrane Endothelial Keratoplasty for Fuchs Endothelial Corneal Dystrophy

PURPOSE

To develop a model to predict corneal improvement after Descemet membrane endothelial keratoplasty (DMEK) for Fuchs endothelial corneal dystrophy (FECD) from Scheimpflug tomography.

DESIGN

Cross-sectional study.

PARTICIPANTS

Forty-eight eyes (derivation group) and 45 eyes (validation group) with a range of severity of FECD undergoing DMEK.

METHODS

Scheimpflug images were obtained before and after DMEK. Before DMEK, pachymetry map and posterior elevation map patterns were quantified by a special image analysis program measuring tomographic features of edema (loss of regular isopachs, displacement of the thinnest point of the cornea, posterior surface depression). Image-derived novel parameters were combined with instrument-derived parameters, and the relative influences of parameters associated with the change in central corneal thickness (CCT) after DMEK in the derivation group were determined by using a gradient boosting machine learning model. The parameters with highest relative influence were then fit in a linear regression model. The derived model was applied to the validation group. Correlations and agreement were assessed between predicted and observed changes in CCT.

MAIN OUTCOME MEASURES

Predictive power (R ²) and mean difference between predicted and observed change in CCT.

RESULTS

The gradient boosting machine model identified 4 novel parameters of isopach circularity and eccentricity and 1 instrument-derived parameter (posterior surface radius); preoperative CCT was a poor predictor. In the derivation group, the model strongly predicted the change in CCT after DMEK (R ² = 0.80; 95% confidence interval [CI], 0.71-0.89) and the mean difference between predicted and observed change was, by definition, 0 μm. When the same 5 parameters were fit to the validation group, the model performed very highly (R ² = 0.89; 95% CI, 0.84-0.94). When the coefficient estimates from the derivation model were used to predict the change in CCT in the validation group, the predictive power was also high (R ² = 0.78; 95% CI, 0.68-0.88), and the mean difference was 4 μm (predicted minus observed).

CONCLUSIONS

Scheimpflug tomography maps of corneas with FECD can predict the improvement in CCT after DMEK, independent of preoperative corneal thickness measurement. The model could be applied in clinical practice or for clinical research of FECD.

Scheimpflug Corneal Densitometry Values and Severity of Guttae in Relation to Visual Acuity in Fuchs Endothelial Corneal Dystrophy

PURPOSE

The purpose of this study was to investigate the association between corneal densitometry (CD) values from Scheimpflug tomography imaging, severity of guttae, and visual acuity in eyes with Fuchs endothelial corneal dystrophy (FECD).

METHODS

This was a retrospective, cross-sectional study. Patients with FECD were examined at the Bascom Palmer Eye Institute from January 2015 to September 2019. We extracted CD values at central annuli of 0-2, 2-6, 6-10 and 10-12 mm from Scheimpflug tomography images. We investigated the association of corrected distance visual acuity (CDVA) with CD values, severity of guttae, central corneal thickness (CCT), cataract grade, refractive error, corneal edema grade, age, and gender using multivariate generalized estimating equation regression models.

RESULTS

One hundred ninety-two eyes from 110 patients were included in this study. Increase in central CD values at the 0 to 2 mm zone (P < 0.001), severity of guttae (P = 0.046), age (P < 0.001), cataract grade (P < 0.001), corneal edema grade (P < 0.001), and type of refractive error (P = 0.008) were significantly associated with decreased CDVA. Central corneal thickness, sex, and the peripheral CD values (2-6, 6-10, and 10-12 mm) were not significantly associated with CDVA (P > 0.05) in the final multivariate regression model.

CONCLUSIONS

Our study demonstrates that central CD values at 0 to 2 mm and severity of guttae are each associated with decreased CDVA in FECD. These findings carry implications for patients with FECD considering surgical intervention for phacoemulsification alone, Descemet stripping only, or endothelial cell transplantation and provide a multifactorial perspective on vision loss in FECD.

Correlation of Clinical Fibrillar Layer Detection and Corneal Thickness in Advanced Fuchs Endothelial Corneal Dystrophy

Central subendothelial geographic deposits are formed as a fibrillar layer (FL) in advanced Fuchs endothelial corneal dystrophy (FECD). Previous studies demonstrated a significant decrease in corneal endothelial cell (CEC) density and an increase in focal corneal backscatter in the FL area. The present study investigated the association of the FL with edema formation and its localization. Patients (n = 96) presenting for Descemet membrane endothelial keratoplasty (DMEK) for advanced FECD were included. Slit-lamp biomicroscopy with FECD grading was followed by Scheimpflug imaging with en face backscatter analysis and pachymetric analysis. FL dimensions were measured, and correlation with pachymetric values was performed. An FL was detected in 74% of all eyes (n = 71). Pachymetric values in FL-positive versus FL-negative eyes were for corneal thickness at the apex (ACT) 614 ± 52 µm and 575 ± 46 µm (p = 0.001), for peripheral corneal thickness at 1 mm (PCT_1mm) 616 ± 50 µm and 580 ± 44 µm (p = 0.002), for PCT_2mm 625 ± 48 µm and 599 ± 41 µm (p = 0.017), for PCT_3mm 651 ± 46 µm and 635 ± 40 µm (p = 0.128) and for PCT_4mm 695 ± 52 µm and 686 ± 43 µm (p = 0.435), respectively. Correlation analysis indicated a weak correlation for the FL maximum vertical caliper diameter with ACT and PCT_1mm values but no further relevant correlations. In FL-positive eyes, increased focal corneal backscatter and increased corneal thickness showed primarily central and inferotemporal localization. In conclusion, Scheimpflug imaging shows an association of the FL with increased corneal thickness in advanced FECD and shows localization of the FL and increased corneal thickness in the central and inferotemporal region. This may provide important information for progression assessment and therapeutic decision making in FECD patients in the future.

Scheimpflug Backscatter Imaging of the Fibrillar Layer in Fuchs Endothelial Corneal Dystrophy

A central collagen-rich subendothelial fibrillar layer (FL) correlates with areas of accentuated loss of corneal endothelial cells in advanced Fuchs endothelial corneal dystrophy (FECD). The present study sought to investigate whether the FL may be visualized by en face Scheimpflug backscatter imaging in vivo.

DESIGN

Retrospective analysis of a prospective observational case series.

METHODS

A total of 34 eyes (34 subjects) undergoing Descemet membrane endothelial keratoplasty (DMEK) surgery with preoperative high-quality Scheimpflug backscatter imaging data were included. The Descemet endothelium complex (DEC) was retrieved during DMEK surgery, and immunofluorescence staining was performed for collagens I, III, and IV. The FL morphology in en face Scheimpflug backscatter and immunofluorescence imaging was compared and agreement of FL parameters was analyzed using intraclass correlation coefficients (ICC) and Bland-Altman plots.

RESULTS

Scheimpflug backscatter imaging delineated the FL in 26 eyes and was FL negative in 8 eyes with deviation compared to immunofluorescence in 1 case and good agreement of morphology characteristics. Horizontal caliper diameter ± SD was 4.84 ± 0.85 mm, vertical caliper diameter was 3.92 ± 0.78 mm, maximum caliper diameter was 5.12 ± 0.82 mm, and surface area was 12.43 ± 4.74 mm². Compared to immunofluorescence imaging, mean difference (95% limits of agreement) and intraclass correlation coefficients were for horizontal caliper diameter 0.13 mm (-0.81 to 1.1 mm) and 0.88, vertical caliper diameter 0.23 mm (-0.76 to 1.2 mm) and 0.81, maximum caliper diameter 0.06 mm (-1.1 to 1.2 mm) and 0.86, and surface area 1.4 mm² (-3.9 to 6.7 mm²) and 0.85.

CONCLUSIONS

Scheimpflug backscatter imaging facilitates visualization of the FL in advanced FECD eyes, offering the potential to identify particularly diseased areas of the FECD endothelium in vivo.

Therapeutic contact lens for Fuchs endothelial corneal dystrophy: Monitoring with Scheimpflug tomopraphy

Purpose

This case report demonstrates the effectiveness of a combined unique soft contact lens design and hypertonic saline at reducing corneal edema symptoms. In addition, this case shows that using tomographic data is invaluable for detecting and monitoring of these presentations.

Observations

A 61 year old patient diagnosed with Fuchs endothelial corneal dystrophy (FECD) presented with complaints over the past year of intermittent blurry, foggy vision upon awakening and glare while driving. Slit lamp examination showed no signs of corneal edema. Data acquired from the Scheimpflug tomographer revealed subclinical signs, including increased corneal thickness, displacement of the thinnest point of the cornea, focal posterior depression, elevated densinometry, "camel's back" sign, irregular isopachs, and a plane slope of pachymetry progression in both eyes. The patient was fit with Therapeutic Hyper-CL™ soft contact lenses for eight days extended wear and instilled 5% sodium chloride six times a day. Visual acuity improved in the right and left eye from 0.5(-2) and 0.5(+1) to 0.4(+2) and 0.3(-1), respectively. Corneal thickness at the thinnest point decreased from 650μm to 632μm-632μm and 604μm in the right and left eye respectively and a significant decrease in total densinometry was noted from 34.7 to 33.8 standardized grayscale units (GSU) to 23.1 and 24 GSU, in the right and left eye respectively. The patient reported a decrease in symptoms and his 8-item Contact Lens Dry Eye Questionnaire (CLDEQ-8) score was 19 after treatment.

Conclusions and importance

Treatment for one week with Therapeutic Hyper-CL™ soft contact lenses combined with 5% sodium chloride decreased corneal edema signs and symptoms. Tomographic data facilitated diagnosis and monitoring of improvement.

Imaging Fuchs Endothelial Corneal Dystrophy in Clinical Practice and Clinical Trials

ABSTRACT

Corneal tomography has an emerging role in the assessment of Fuchs endothelial corneal dystrophy (FECD) in clinical practice and potentially for future clinical trials. Posterior elevation and pachymetry maps derived from elevation based Scheimpflug tomography can detect early corneal edema, even at a subclinical stage, enabling clinicians to better counsel patients about their vision and the risk of disease progression with and without cataract surgery. Tomographic imaging provides a functional assessment of corneal endothelial health, and could enable objective assessment of FECD progression, or regression, in response to novel therapeutic interventions. Clinicians and investigators should adopt Scheimpflug imaging for the assessment of FECD over traditional morphologic imaging modalities.

Demographic profile and clinical course of Fuchs endothelial corneal dystrophy in Mexican patients

PURPOSE

To describe the demographic characteristics and clinical course of Fuchs endothelial corneal dystrophy (FECD) in a Mexican-mestizo population.

METHODS

A retrospective observational and longitudinal study was performed in consecutive patients with the clinical diagnosis of Fuchs endothelial corneal dystrophy seen at our institution. Initial and last follow-up best-corrected visual acuity, slit-lamp findings, and specular microscopy endothelial morphometric parameters were analyzed.

RESULTS

One hundred and two eyes belonging to 51 patients were included in the analysis. Median age at the time of diagnosis was 69 years (range, 25-87 years) with a female-to-male ratio of 3.3:1. Visual loss (40%) followed by glare (13.3%) and fluctuating matutine vision loss (13.3%) was the most common complaints at presentation. Regarding FECD staging, 65 (63.7%) were classified as stage-I FECD, 21 (20.6%) stage-II, and 15 (14.7%) as stage-III. A high percentage of eyes (44.1%) presented visual impairment ( ≤ 20/50) at presentation, and the presence of isolated corneal guttata was the most common stage of presentation (64%) at slit-lamp examination. While fifty-nine (57.8%) eyes did not require any medical or surgical management, 17 (16.7%) eyes were managed with hypertonic saline eyedrops alone or in combination with bandage contact lens, and 18 (17.6%) required corneal transplantation. Penetrating keratoplasty alone (8 eyes, 44.4%), or in combination with cataract extraction and intraocular lens implantation (3 eyes, 16.7%), was the most frequent surgical technique performed.

CONCLUSION

Demographical characteristics of Fuchs dystrophy regarding age at presentation, gender distribution, and clinical stage at the time of diagnosis did not differ significantly from other international reports. Almost 20% of these patients will require keratoplasty during the disease, emphasizing the need for safer and more reproducible keratoplasty techniques.

A Risk Prediction Model for Endothelial Keratoplasty After Uncomplicated Cataract Surgery in Fuchs Endothelial Corneal Dystrophy

PURPOSE

To develop a risk prediction model for endothelial keratoplasty (EK) after uncomplicated cataract surgery in Fuchs endothelial corneal dystrophy (FECD) using Scheimpflug imaging.

DESIGN

Prospective, observational cohort study.

METHODS

The study was conducted at the Ramón y Cajal University Hospital (Madrid, Spain) on 127 eyes from 93 consecutive patients with vision loss, FECD, and cataracts.

OBSERVATION

We assessed the corneas using Scheimpflug imaging pachymetry and elevation maps for loss of regular isopachs, displacement of the thinnest point, and posterior surface depression according to the Mayo Clinic subclinical corneal edema classification. We also recorded other preoperative data. Primary Endpoints: The primary endpoint was the need for EK after uncomplicated phacoemulsification within 2 years (median duration, 18 months). We calculated the risk using hazard ratios and the Kaplan-Meier cumulative incidence risk.

RESULTS

Forty-four participants required EK, and those eyes with 1, 2, or all 3 tomographic features had a hazard risk of 21.8, 57.2, and 76.5, respectively (P < .005), compared with those eyes with normal tomographic patterns. The best predictive model was based on the number of tomographic features simultaneously present in an eye and the central corneal thickness (CCT) at the pupillary center. We aimed to develop a risk score from 0 to 8. The cumulative risk for EK ranged from virtually 0 for risk scores <4 to almost 100% for those with a score of 8.

CONCLUSIONS

The combination of CCT values and tomographic features can be employed to make valid predictions of the risk of requiring EK after phacoemulsification.

Separate Detection of Stromal and Epithelial Corneal Edema on Optical Coherence Tomography Using a Deep Learning Pipeline and Transfer Learning

The accurate detection of corneal edema has become a topic of growing interest with the generalization of endothelial keratoplasty. Despite recent advances in deep learning for corneal edema detection, the problem of minimal edema remains challenging. Using transfer learning and a limited training set of 11 images, we built a model to segment the corneal epithelium, which is part of a three-model pipeline to detect corneal edema. A second and a third model are used to detect edema on the stroma alone and on the epithelium. A validation set of 233 images from 30 patients consisting of three groups (Normal, Minimal Edema and important Edema) was used to compare the results of our new pipeline to our previous model. The mean edema fraction (EF), defined as the number of pixels detected as edema divided by the total number of pixels of the cornea, was calculated for each image. With our previous model, the mean EF was not statistically different between the Normal and Minimal Edema groups (p = 0.24). With the current pipeline, the mean EF was higher in the Minimal Edema group compared to the Normal group (p < 0.01). The described pipeline constitutes an adjustable framework for the detection of corneal edema based on optical coherence tomography and yields better performances in cases of minimal or localized edema.

Corneal Edema Visualization With Optical Coherence Tomography Using Deep Learning: Proof of Concept

PURPOSE

Optical coherence tomography (OCT) is essential for the diagnosis and follow-up of corneal edema, but assessment can be challenging in minimal or localized edema. The objective was to develop and validate a novel automated tool to detect and visualize corneal edema with OCT.

METHODS

We trained a convolutional neural network to classify each pixel in the corneal OCT images as "normal" or "edema" and to generate colored heat maps of the result. The development set included 199 OCT images of normal and edematous corneas. We validated the model's performance on 607 images of normal and edematous corneas of various conditions. The main outcome measure was the edema fraction (EF), defined as the ratio between the number of pixels labeled as edema and those representing the cornea for each scan. Overall accuracy, sensitivity, specificity, and area under the receiver operating characteristic curve were determined to evaluate the model's performance.

RESULTS

Mean EF was 0.0087 ± 0.01 in the normal scans and 0.805 ± 0.26 in the edema scans (P < 0.0001). Area under the receiver operating characteristic curve for EF in the diagnosis of corneal edema in individual scans was 0.994. The optimal threshold for distinguishing normal from edematous corneas was 6.8%, with an accuracy of 98.7%, sensitivity of 96.4%, and specificity of 100%.

CONCLUSIONS

The model accurately detected corneal edema and distinguished between normal and edematous cornea OCT scans while providing colored heat maps of edema presence.

New severity grading system for Fuchs endothelial corneal dystrophy using anterior segment optical coherence tomography

PURPOSE

To report a new severity grading system for Fuchs endothelial corneal dystrophy (FECD) using anterior segment optical coherence tomography (AS-OCT).

METHODS

This observational case series included 75 eyes of 43 patients with FECD and 33 eyes of 33 healthy subjects. Pachymetry and posterior elevation maps were used to determine the AS-OCT-based grading scores. FECD severity was graded from 0-3 as follows: 0, normal; 1, guttae only; 2, stromal oedema; and 3, epithelial and stromal oedema. We further investigated the central corneal thickness (CCT), thinnest corneal thickness (TCT), anterior and posterior best-fit spheres (BFS), and the distance between the central cornea and the thinnest point.

RESULTS

Thirty-three eyes were graded as 0, four as 1, thirteen as 2, fourteen as 3, twenty-nine as 4, eleven as 5 and four as 6 by the modified Krachmer grade. Thirty-three, 41, 30 and 4 eyes were graded as 0, 1, 2 and 3, respectively, by the AS-OCT-based grading system. The inter-observer agreement was 100% for the AS-OCT-based grading system. The CCT, TCT, posterior BFS, and distance between the central cornea and thinnest point were significantly different between AS-OCT-based grades (p = 0.0001, 0.0001, 0.0036 and 0.0001, respectively). Anterior BFS was not significantly different with the AS-OCT-based grades (p = 0.1184).

CONCLUSION

We devised a new severity grading using only objective evaluation and quantitatively demonstrated corneal thickening, predominant flattening of the posterior corneal surface compared with the anterior surface, and displacement of the thinnest point away from the central cornea with FECD progression.

Corneal pachymetry by AS-OCT after Descemet's membrane endothelial keratoplasty

Corneal thickness (pachymetry) maps can be used to monitor restoration of corneal endothelial function, for example after Descemet’s membrane endothelial keratoplasty (DMEK). Automated delineation of the corneal interfaces in anterior segment optical coherence tomography (AS-OCT) can be challenging for corneas that are irregularly shaped due to pathology, or as a consequence of surgery, leading to incorrect thickness measurements. In this research, deep learning is used to automatically delineate the corneal interfaces and measure corneal thickness with high accuracy in post-DMEK AS-OCT B-scans. Three different deep learning strategies were developed based on 960 B-scans from 50 patients. On an independent test set of 320 B-scans, corneal thickness could be measured with an error of 13.98 to 15.50 μm for the central 9 mm range, which is less than 3% of the average corneal thickness. The accurate thickness measurements were used to construct detailed pachymetry maps. Moreover, follow-up scans could be registered based on anatomical landmarks to obtain differential pachymetry maps. These maps may enable a more comprehensive understanding of the restoration of the endothelial function after DMEK, where thickness often varies throughout different regions of the cornea, and subsequently contribute to a standardized postoperative regime.

Incidence and Risk Factors of Corneal Endothelial Failure after Phacoemulsification in Patients with Fuchs Endothelial Corneal Dystrophy: A 13-Year Retrospective Cohort

Objective

To evaluate the incidence of corneal endothelial failure (CEF) and determine the risk factors of developing CEF after phacoemulsification in patients with Fuchs endothelial corneal dystrophy (FECD).

Methods

A retrospective chart review of 2873 patients who underwent phacoemulsification with intraocular lens (IOL) implantation was conducted at Ramathibodi Hospital, Bangkok, Thailand from January 2007 to December 2019. Patient baseline characteristics, underlying diseases, levels of nuclear cataract, pre-operative specular microscopic parameters, intraoperative information (cumulative dissipated energy [CDE], mode of phacoemulsification, and complications), and occurrence of CEF were collected. Data were analyzed using Kaplan–Meier (KM) method and Cox proportional hazard model.

Results

Ninety-four patients diagnosed with FECD at follow-up time of more than 6 months were included for analysis. Mean age was 70.3 ± 7.7 years with female predominance (81.91%). Median follow-up time was 3.2 years. Nine (9.57%) patients developed CEF during follow-up period. The overall incidence rate of CEF after phacoemulsification was 26 per 1000 person years (95% confidence interval [CI]; 14 to 49 per 1000 person years). Only intraoperative complications showed significant association with CEF at hazard ratio (HR) of 6.03 (95% CI 1.50 to 26.50). No significant association was found among age, gender, underlying diseases, level of nuclear sclerosis and pre-operative specular microscopic parameters.

Conclusion

Intraoperative complications should be considered as an important risk factor for developing post-operative CEF in FECD patients. Apart from assessing pre-operative parameters, surgeons should also consider the possibility of and try to avoid any intra-operative complications, which could potentially result in CEF after phacoemulsification for each individual patient.

Collagen Remodeling Plays a Pivotal Role in Endothelial Corneal Dystrophies

Purpose

To elucidate the collagen structure in the Descemet membrane (DM) of the human cornea and to characterize its rearrangement in patients with endothelial corneal dystrophies.

Methods

Corneas from nine human donors and dystrophic DMs removed from 16 affected eyes of 13 patients by endothelial keratoplasty (DMEK) were investigated using a correlative RT-qPCR and label-free two-channel multiphoton microscopy (MPM) setup. Although collagen formation was visualized by second harmonic generation, the cellular structure was determined by autofluorescence.

Results

The DM of the human donor cornea was characterized by a consistent pattern of fine hexagonal collagen structures that form a supportive scaffold for the endothelial cells. Accordingly, network-forming collagens (8A1 and 8A2) but less fibrillar collagens (only 1A2) were expressed. DMEK resulted in significant (P < 0.0001) improvement of best-corrected visual acuity. In the removed dystrophic DMs, MPM analyses revealed collagen rearrangement in addition to loss of endothelial cells and the development of guttae. MPM analyses of the whole patient's DM demonstrated this collagen remodeling in its entirety and facilitated correlation to Scheimpflug corneal tomography. In most DMs a unique honeycomb collagen network was identified, with distinct bundles surrounding the guttae and correlating with expression of fibrillar collagens (1A1). Conversely, some DMs showed either reduced collagen on MPM and RT-qPCR analysis or diffuse thickening and storage of extracellular matrix.

Conclusions

The collagen structure of the DM and its adaptive remodeling in endothelial corneal dystrophies has been characterized for the first time here and will facilitate individual therapeutic approaches.

Endothelial Keratoplasty Update 2020

ABSTRACT

Endothelial keratoplasty has revolutionized the treatment of corneal endothelial dysfunction and lowered the threshold for treatment by providing rapid visual rehabilitation and setting a high standard for safety and efficacy. Over time, endothelial keratoplasty techniques have evolved toward the use of thinner tissue to optimize visual outcomes; refinements have facilitated donor tissue preparation, handling, and attachment; and adaptations have expanded utilization in eyes with challenging ocular anatomy. Despite early concerns about graft longevity, emerging 10-year endothelial cell loss and graft survival data have been encouraging. A shortage of human donor corneas restricts utilization in many areas of the world and is driving a search for keratoplasty alternatives. Further work is needed to expand the donor supply, minimize impediments to adoption, optimize graft survival, and improve refractive predictability.

Predicting Edema Resolution After Descemet Membrane Endothelial Keratoplasty for Fuchs Dystrophy Using Scheimpflug Tomography

Importance

Predicting the extent of corneal edema resolution after Descemet membrane endothelial keratoplasty (DMEK) may help in preoperative decision-making by identifying patients who may benefit from restoring endothelial function.

Objective

To develop and validate a predictive model for edema resolution after DMEK using Scheimpflug tomographic imaging.

Design, Setting, and Participants

Two prospective studies recruited participants with advanced Fuchs dystrophy at a university-based tertiary referral center between July 1, 2017, and August 31, 2019. Analyses were designed in November 2019 and completed on June 30, 2020. Development of a predictive model using linear least absolute shrinkage and selection operator regression was conducted in a derivation cohort (100 eyes). Overall performance, discrimination, and calibration were tested in the separate validation cohort (32 eyes).

Exposures

Preoperative Scheimpflug parameters and patient-reported visual disability were considered as potential predictors of edema resolution: (1) tomographic features (irregularity of lines of equal corneal thickness, displacement of the thinnest point of corneal thickness from the inferior-temporal quadrant, and absolute amount of focal posterior corneal depression), (2) standardized anterior and posterior corneal backscatter, (3) preoperative central corneal thickness, and (4) Fuchs dystrophy-specific visual disability.

Main Outcomes and Measures

Decrease in central corneal thickness after DMEK indicative of edema resolution.

Results

Of the 88 patients included in the analysis, 54 were women (61%); median age was 68 years (interquartile range [IQR], 59-76 years). A median of 13 months after DMEK (IQR, 9-16 months), median corneal thickness was 77 μm lower (IQR, 51-94 μm) in the derivation cohort and 75 μm lower in the validation cohort (IQR, 54-96 μm) than before surgery. Per 10-μm edema resolution, eyes gained 0.66 Early Treatment Diabetic Retinopathy Study letters (95% CI, 0.09-1.23) in best-corrected visual acuity. Three tomographic features were present in 68 of 100 eyes (68%) in the derivation cohort and in 18 of 32 eyes (56%) in the validation cohort before DMEK and in only 1 of 132 eyes (1%) after DMEK. To predict edema resolution after DMEK based on preoperative assessment, 5 variables were selected by the statistical learning algorithm: nonparallel isopachs, focal posterior depression, anterior and posterior corneal backscatter, and central corneal thickness. In the separate validation cohort, the model showed high overall performance, discrimination, and calibration.

Conclusions and Relevance

These post hoc analyses of prospective cohorts support a model for use in the prediction of edema resolution after DMEK using Scheimpflug measurement to identify patients benefitting most from DMEK.

Corneal Analysis with Swept Source Optical Coherence Tomography in Patients with Coexisting Cataract and Fuchs Endothelial Corneal Dystrophy

This study focused on defining the characteristic features of keratometry and pachymetry elevation maps based on swept source optical coherence tomography (SS OCT) in Fuchs endothelial corneal dystrophy (FECD) eyes with a coexisting cataract. 70 eyes of 35 patients diagnosed with FECD and a coexisting cataract and 70 control eyes were included in this prospective, controlled, observational, cross-sectional study. Features characteristic of intermediately affected eyes included an increased corneal thinnest thickness (CTT) (p = 0.01), 3 and 6 mm asymmetry (p < 0.0001), higher order Fourier indices (p < 0.05 and p ≤ 0.0001, respectively), chord µ, and a posterior Ectasia Screening Index (pESI) (p < 0.01). The lack of agreement between the anterior and posterior elevation map and a significant area of negative values in the posterior map were detected. In advanced FECD eyes, our study additionally revealed decreased posterior keratometry steep (Ks), keratometry flat (Kf), keratometry average (AvgK), eccentricity (Ecc), an increased corneal apex thickness (CAT), and decreased 3 and 6 mm posterior spherical indices (p < 0.0001 for all of the above). Characteristic features of subclinical FECD, independent of the corneal thickness, can be detected by SS OCT and should be considered during the preoperative assessment of patients with a coexisting cataract.

Automated Clinical Assessment of Corneal Guttae in Fuchs Endothelial Corneal Dystrophy

PURPOSE

To describe the validation and implementation of an automated system for the detection and quantification of guttae in Fuchs endothelial corneal dystrophy (FECD).

DESIGN

Observational reliability study.

METHODS

Patients with FECD underwent retroillumination corneal photography, followed by determination of the distributions and sizes of corneal guttae by an automated image analysis algorithm. Performance of the automated system was assessed via (1) validation against manual guttae segmentation, (2) reproducibility studies to ensure consistency, and (3) evaluation for agreement with the Krachmer scale. It was then deployed to perform large-scale guttae assessment with anatomic subregion analysis in a batch of 40 eyes.

RESULTS

Compared to manual segmentation, the automated system was reasonably accurate in identifying the correct number of guttae (mean count of 78 guttae per 1 × 1 mm test frame, overestimation: +10 per frame), but had a tendency to significantly overestimate guttae size (mean guttae size 1073 μm², overestimation: +255 μm²). Automated measurements of guttae counts and sizes were reproducible within a 1% discrepancy range across repeat intra-eye assessments. Automated guttae counts, interguttae distances, and density of interguttae gaps lesser than 40 μm (ie, D40 density) were highly correlated with the Krachmer scale (P < .001 for all). Large-scale guttae assessment demonstrated the automated system's potential to selectively identify a region of the corneal endothelium most affected by densely packed guttae.

CONCLUSIONS

Automated guttae assessment facilitates the precise identification and quantification of guttae characteristics in FECD patients. This can be used clinically as a personalized descemetorrhexis zone for Descemet stripping only and/or Descemet membrane transplantation.

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

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

Repeatability of Scheimpflug Tomography for Assessing Fuchs Endothelial Corneal Dystrophy

PURPOSE

To determine if agreement between subjective interpretations of Scheimpflug tomography maps of corneas with Fuchs endothelial corneal dystrophy (FECD) is affected by daily and hourly changes in corneal edema.

DESIGN

Reliability analysis.

METHODS

Scheimpflug imaging pachymetry and posterior elevation maps of corneas with a range of severity of FECD were evaluated in a randomized manner for the presence of 3 tomographic features of edema. Agreement between interpretations of 1 masked observer was assessed (percentage, and κ-statistic with 95% confidence interval) for images taken within minutes on the same day, for images taken at a similar time on a different day, and for images taken over the course of a morning. Intra- and interobserver agreement was also assessed.

RESULTS

Interpretations for individual tomographic features agreed for ≥88% of images (κ ≥ 0.75) taken within minutes on the same day; complete disagreement (ie, disagreement for all 3 tomographic features in an image) occurred in ≤3% of images. Interpretations agreed for ≥77% of images (κ ≥ 0.52) taken at a similar time on a different day; complete disagreement did not occur. Interpretations agreed for ≥81% of images (κ ≥ 0.61) taken over the course of a morning; complete disagreement occurred in ≤6% of images. Intraobserver agreement was ≥93% (κ ≥ 0.83) and interobserver agreement was ≥93% (κ ≥ 0.66); complete disagreement did not occur.

CONCLUSIONS

Subjective interpretation of Scheimpflug images in FECD is highly repeatable for disease classification. Although small variations in interpretations resulted from pathophysiologic changes in corneal hydration and other factors, clinically significant disagreements in interpretation were uncommon and therefore unlikely to affect clinical decision-making.