Fuchs Endothelial Corneal Dystrophy Research Articles

Fourier Analysis on Regular and Irregular Astigmatism of Anterior and Posterior Corneal Surfaces in Fuchs Endothelial Corneal Dystrophy

To conduct Fourier analysis on regular and irregular astigmatism of the anterior and posterior corneal surfaces using anterior segment optical coherence tomography in patients with Fuchs endothelial corneal dystrophy (FECD) DESIGN: Observational case series. This study included 75 eyes of 43 FECD patients and 34 eyes of 34 healthy subjects in Osaka University Hospital. Corneal dioptric data from the central 6-mm zone of the anterior and posterior corneal surface were expanded into spherical, regular astigmatism, asymmetry, and higher-order irregularity components using Fourier analysis. We analyzed the association between each component and modified Krachmer grade. There were significant differences in regular astigmatism, asymmetry, and higher-order irregularity components of the anterior corneal surface, and spherical, regular astigmatism, asymmetry, and higher-order irregularity components of the posterior corneal surface among modified Krachmer grades (P= .036, <.001, <.001, <.001, <.001, <.001, and <.001, respectively). Asymmetry component of the anterior and posterior corneal surfaces gradually increased with FECD progression. Higher-order irregularity components of the anterior and posterior corneal surfaces drastically increased in Grade 6. Many eyes had an axis of 0°-180° for the asymmetry component of the anterior surface and 180°-360° for that of the posterior surface. Patients with severe FECD had a larger amount of asymmetry and higher-order irregularity components of the anterior and posterior corneal surfaces. Patients with FECD up to Grade 5 were characterized by anterior and posterior flattening in the inferior cornea, and those with Grade 6 showed irregularity in the anterior and posterior corneal surfaces.

Clinical outcomes of pre-loaded ultra-thin DSAEK and pre-loaded DMEK

ObjectiveTo compare clinical outcomes and complications between pre-loaded ultra-thin Descemet stripping automated endothelialkeratoplasty (pl-UT-DSAEK) and pre-loaded Descemet membrane endothelial keratoplasty (pl-DMEK).Methods and analysisComparative study in patients with endothelial dysfunction associated...

Descemet Membrane Endothelial Keratoplasty in Asian Eyes

Descemet membrane endothelial keratoplasty (DMEK) has become the treatment of choice for endothelial diseases such as Fuchs endothelial corneal dystrophy (FECD), especially in the United States and Europe. In this review, we give an overview of current knowledge about DMEK in Asian eyes and describe novel surgical modifications of this technique for these cases. Although many scientific reviews about DMEK in Caucasian eyes have already been published, there is still little knowledge about clinical outcomes of DMEK in Asian eyes. This is of particular importance, as there are substantial differences between DMEK in Asian and Caucasian eyes. Bullous keratopathy is the main indication for endothelial keratoplasty in Asia, whereas it is FECD in Caucasian countries. Considering etiological and anatomical differences, we have adapted DMEK for Asian eyes and have developed several technical modifications to improve clinical outcome. Our work might be helpful in performing successful DMEK in the Asian setting.

Fibrillar Layer as a Marker for Areas of Pronounced Corneal Endothelial Cell Loss in Advanced Fuchs Endothelial Corneal Dystrophy

We sought to assess the correlation of corneal endothelial cell (CEC) density to alterations of collagen composition of Descemet membrane (DM) in advanced Fuchs endothelial corneal dystrophy (FECD) and to image such changes by slit-lamp biomicroscopy invivo. Prospective, observational consecutive case series. Fifty eyes (50 subjects) with advanced FECD were enrolled. After slit-lamp biomicroscopy and corneal Scheimpflug imaging, the Descemet endothelium complex (DEC) was retrieved during DM endothelial keratoplasty (DMEK) surgery. The expression of collagens I, III, and IV (COL I, COL III, and COL IV) and corresponding CEC density were analyzed by immunofluorescence flat mount-staining. Presence, diameter and surface area of collagen expression, and CEC density served as the main outcome measures. Immunofluorescence staining revealed central coherent collagen positive areas (mean surface area= 10mm2 ± 6mm2) corresponding to a fibrillar layer burying the guttae of DM in 84% (42/50) of DECs. CEC density overlying the fibrillar layer compared with the periphery was significantly reduced (-54.8%, P< .0001) with a steep decline of CEC density at its borders. Subgroup analysis revealed that the fibrillar layer may be imaged by slit-lamp biomicroscopy invivo with significant positive correlation of mean maximum diameter detected by slit-lamp biomicroscopy (dSL max= 4.1mm ± 0.9mm) and by immunofluorescence staining (dIF max= 4.7mm ± 1.1mm; r= 0.76; P= .001). A fibrillar layer with a clear geographic pattern marks areas of pronounced loss of CEC density in advanced FECD eyes and may be imaged by slit-lamp biomicroscopy invivo.

Trinucleotide Repeat-Targeting dCas9 as a Therapeutic Strategy for Fuchs' Endothelial Corneal Dystrophy.

PurposeFuchs’ endothelial corneal dystrophy (FECD) is the leading indication for corneal transplantation. Seventy percent of cases are caused by an intronic CTG triplet repeat expansion in the TCF4 gene that results in accumulation of pathogenic expanded CUG repeat RNA (CUGexp) as nuclear foci in corneal endothelium. A catalytically dead Cas9 (dCas9) can serve as an effective guide to target genomic DNA or RNA transcripts. Here, we examined the utility of the clustered regularly interspaced short palindromic repeats (CRISPR)-dCas9 system to effectively target and reduce CUGexp.MethodsWe delivered dCas9 and repeat-targeting single guide RNA (sgRNA) expression plasmids to patient-derived endothelial cells using lipofection or lentiviral transduction. We used fluorescence in situ hybridization (FISH) and RNA dot-blot hybridization to quantify CUGexp foci and repeat RNA levels, respectively. TCF4 expression levels were assessed using quantitative PCR (qPCR).ResultsUsing FISH, we found that expression of both dCas9 and a (CAG)n sgRNA complementary to CUGexp are necessary to reduce foci. We observed a reduction in percentage of cells with foci from 59% to 5.6% and number of foci per 100 cells from 73.4 to 7.45 (P < 0.001) in cells stably expressing dCas9-(CAG)n sgRNA but saw no decrease in cells expressing dCas9-(CUG)n sgRNA or nontargeting control sgRNA. In cells with dCas9-(CAG)n sgRNA, we detected a reduction in CUGexp RNA by dot-blot without any reduction in TCF4 mRNA levels using qPCR.ConclusionsUsing CRISPR-dCas9 to target the trinucleotide repeat is a promising treatment for FECD contingent on effective in vivo delivery.Translational RelevanceThis work advances a gene therapy for a common age-related degenerative disorder.

Update on the Surgical Management of Fuchs Endothelial Corneal Dystrophy.

Fuchs endothelial corneal dystrophy (FECD) is the most common posterior corneal dystrophy and the leading indication for corneal transplantation in the United States. FECD is slowly progressive, and patients develop gradual corneal endothelial decompensation, eventually resulting in failure of the endothelium to maintain corneal deturgescence. Medical management consists of topical hyperosmotic agents to facilitate dehydration of the cornea, but surgical intervention is often required to regain corneal clarity. The surgical management of FECD has evolved over the past two decades as corneal transplantation techniques have allowed for more selective keratoplasty and replacement of only the diseased layers of the cornea. Prior surgical management consisted of penetrating keratoplasty (PK) that carried significant intraoperative risks associated with “open sky” as well as postoperative risks of graft rejection, wound dehiscence, postoperative astigmatism, and prolonged visual rehabilitation. In the past 15 years, endothelial keratoplasty (EK) has become the treatment of choice for endothelial disease, significantly reducing the risks associated with the surgical treatment of FECD. Here we discuss the current surgical management of FECD, including the introduction of Descemet stripping only (DSO), and highlight future investigative efforts.

Small Incision Lenticule Extraction (SMILE) in Patients with Corneal Guttae.

PurposeTo report 12-month results of small incision lenticule extraction (SMILE) in the treatment of myopia with corneal guttae (CG).MethodsWe conducted a retrospective analysis of 12 eyes from six patients who had preoperative CG without clinical sign of Fuchs’ endothelial corneal dystrophy (FECD) and had SMILE for correction of myopia. Preoperative and 12-month postoperative measurements included uncorrected distance visual acuity (UDVA), spherical equivalent (SE), endothelial cell density (ECD), the coefficient of variation (CV), the percentage of hexagonal cells (HEX), and central corneal thickness (CCT). The changes in ECD, CV, HEX, and CCT after SMILE were subjected to statistical analysis.ResultsTwelve months postoperatively, the mean SE was −0.10 ± 0.32 D and all eyes had a UDVA of 0 logMAR or better. No eyes developed corneal edema or other complication during the follow-up period. There were no significant changes in the ECD, CV, or HEX at 12 months (all p>0.05).ConclusionSMILE yielded improvement in visual acuity and no adverse effects to corneal endothelial cells were found when correcting myopia or myopic astigmatism in patients with CG. However, studies with a greater number of patients and longer follow-up periods are needed to establish the long-term outcomes and safety.

Descemet Stripping Only Supplemented With Topical Ripasudil for Fuchs Endothelial Dystrophy 12-Month Outcomes of the Sydney Eye Hospital Study.

To report early safety and efficacy of Descemet stripping only (DSO) supplemented with ripasudil. A pre-post clinical trial with a historical control group for time to heal and cell count parameters. The study received ethics approval and was conducted with oversight of a data safety monitoring board. All enrolled patients had a superior endothelial cell count of >1000 cells/mm2 and were symptomatic from the presence of central guttata degrading vision and/or producing glare. DSO was carried out with a peeling technique and not combined with any other intervention. Ripasudil 0.4% was applied topically from day 1 postoperatively at a dose of 6 times/d until corneal clearance. Cases with relapse of edema were permitted to restart on ripasudil at a reduced dose of 2 drops/d for a further 2 weeks. Stopping rules with progression to a corneal graft were established. Baseline ocular and systemic investigations were carried out and repeated at varying intervals to monitor for local and systemic adverse events. Twenty-three eyes of 23 patients met the inclusion criteria and underwent DSO. Twenty-two of 23 eyes achieved corneal clearance at a mean time of 4.1 weeks. In all patients achieving clearance, improvement in vision was recorded. Improvement in mean uncorrected visual acuity was 0.20 Logarithm of the minimum angle of resolution (LogMar), and improvement in mean best spectacle corrected visual acuity was 0.156 LogMar. One patient failed to clear and underwent Descemet membrane endothelial keratoplasty at week 12. Twenty-one of 22 patients achieving corneal clearance expressed satisfaction with the procedure. The commonest systemic side effect of topical ripasudil was gastrointestinal upset (24%), and the commonest local side effect was ocular irritation (43%). No patient experienced a serious adverse event in the course of the trial. Thirty-nine percent of patients experienced a relapse of edema on ceasing ripasudil, with clearance again on recommencing. This trial of DSO supplemented with ripasudil included local and systemic safety analysis. We judge that this treatment option is emerging as a reliable intervention for select patients with Fuchs' Endothelial Corneal Dystrophy (FECD) with an acceptable safety profile. The observation of relapse edema is strong evidence of a drug effect. The longevity of these results remains unknown.

TCF4-mediated Fuchs endothelial corneal dystrophy: Insights into a common trinucleotide repeat-associated disease.

Fuchs endothelial corneal dystrophy (FECD) is a common cause for heritable visual loss in the elderly. Since the first description of an association between FECD and common polymorphisms situated within the transcription factor 4 (TCF4) gene, genetic and molecular studies have implicated an intronic CTG trinucleotide repeat (CTG18.1) expansion as a causal variant in the majority of FECD patients. To date, several non-mutually exclusive mechanisms have been proposed that drive and/or exacerbate the onset of disease. These mechanisms include (i) TCF4 dysregulation; (ii) toxic gain-of-function from TCF4 repeat-containing RNA; (iii) toxic gain-of-function from repeat-associated non-AUG dependent (RAN) translation; and (iv) somatic instability of CTG18.1. However, the relative contribution of these proposed mechanisms in disease pathogenesis is currently unknown. In this review, we summarise research implicating the repeat expansion in disease pathogenesis, define the phenotype-genotype correlations between FECD and CTG18.1 expansion, and provide an update on research tools that are available to study FECD as a trinucleotide repeat expansion disease. Furthermore, ongoing international research efforts to develop novel CTG18.1 expansion-mediated FECD therapeutics are highlighted and we provide a forward-thinking perspective on key unanswered questions that remain in the field.

Automated Clinical Assessment of Corneal Guttae in Fuchs Endothelial Corneal Dystrophy

To describe the validation and implementation of an automated system for the detection and quantification of guttae in Fuchs endothelial corneal dystrophy (FECD). Observational reliability study. 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. Compared to manual segmentation, the automated system was reasonably accurate in identifying the correct number of guttae (mean count of 78 guttae per 1× 1mm test frame, overestimation:+10 per frame), but had a tendency to significantly overestimate guttae size (mean guttae size 1073μm2, overestimation:+255μm2). 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 40μm (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. 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.

Energy Shortage in Human and Mouse Models of SLC4A11-Associated Corneal Endothelial Dystrophies.

PurposeTo elucidate the molecular events in solute carrier family 4 member 11 (SLC4A11)-deficient corneal endothelium that lead to the endothelial dysfunction that characterizes the dystrophies associated with SLC4A11 mutations, congenital hereditary endothelial dystrophy (CHED) and Fuchs endothelial corneal dystrophy 4.MethodsComparative transcriptomic analysis (CTA) was performed in primary human corneal endothelial cells (pHCEnC) and murine corneal endothelial cells (MCEnC) with normal and reduced levels of SLC4A11 (SLC4A11 KD pHCEnC) and Slc4a11 (Slc4a11−/− MCEnC), respectively. Validation of differentially expressed genes was performed using immunofluorescence staining of CHED corneal endothelium, as well as western blot and quantitative PCR analysis of SLC4A11 KD pHCEnC and Slc4a11−/− MCEnC. Functional analyses were performed to investigate potential functional changes associated with the observed transcriptomic alterations.ResultsCTA revealed inhibition of cell metabolism and ion transport function as well as mitochondrial dysfunction, leading to reduced adenosine triphosphate (ATP) production, in SLC4A11 KD pHCEnC and Slc4a11−/− MCEnC. Co-localization of SNARE protein STX17 with mitochondria marker COX4 was observed in CHED corneal endothelium, as was activation of AMPK–p53/ULK1 in both SLC4A11 KD pHCEnC and Slc4a11−/− MCEnC, providing additional evidence of mitochondrial dysfunction and mitophagy. Reduced Na+-dependent HCO3− transport activity and altered NH4Cl-induced membrane potential changes were observed in Slc4a11−/− MCEnC.ConclusionsReduced steady-state ATP levels and subsequent activation of the AMPK–p53 pathway provide a link between the metabolic functional deficit and transcriptome alterations, as well as evidence of insufficient ATP to maintain the Na+/K+-ATPase corneal endothelial pump as the cause of the edema that characterizes SLC4A11-associated corneal endothelial dystrophies.

Corneal optical density in Fuchs endothelial dystrophy determined by anterior segment optical coherence tomography.

In this study, we propose a method to grade corneal stromal opacity using optical density measurements by anterior segment optical coherence tomography (AS-OCT) and validate the approach in Fuchs endothelial corneal dystrophy (FECD). A retrospective analysis of human corneal OCT scans was performed on 48 eyes of 32 patients with FECD and 33 control eyes of 21 patients using the Carl Zeiss Cirrus HD-OCT 5000. In addition, corneal edema in fresh rabbit cadaver eyes was artificially induced by distilled water and imaged with the Thorlabs TELESTO-II spectral domain OCT at different time points during saturation. The increase of opacity due to corneal edema was proposed to directly correlate with enhanced reflectivity sites in the OCT images, corresponding to higher optical density. The increase was determined as the image area above a statistically established gray-scale value using ImageJ and correlated with other disease characteristics. Optical densities in human corneas showed significant differences between FECD patients and the control group (p = 0.002). The increased optical densities determined in FECD corneas correlated well with other disease characteristics such as corneal pachymetry or visual acuity. Likewise, rabbit corneas showed a time dependent increase in thickness and in corneal optical density during soaking in distilled water. This study presents corneal optical density by AS-OCT as an objective value for corneal changes in FECD. Complementing other diagnostic tools in FECD the assessment of corneal optical density may identify progression of FECD, gauge novel therapeutic strategies and support risk and benefit analyses for corneal surgery.

Three-Year Outcomes of Tri-Folded Endothelium-In Descemet Membrane Endothelial Keratoplasty With Pull-Through Technique

To assess the 3-year outcomes of tri-folded endothelium-in Descemet membrane endothelial keratoplasty (DMEK) using bimanual pull-through delivery technique. Interventional case series. In this single-center study, we included 153 consecutive eyes that underwent DMEK for various indications (Fuchs endothelial corneal dystrophy [FECD]: n= 111; bullous keratopathy [BK]: n= 24; and failed graft: n= 18). DMEK grafts were loaded into a disposable cartridge in a tri-folded, endothelium-in configuration and delivered using bimanual pull-through technique. Main outcome measures were graft preparation and unfolding times, best spectacle-corrected visual acuity (BSCVA), endothelial cell density (ECD), and graft survival. Mean graft preparation time was 5.9 ± 1.1minutes; and mean graft unfolding time was 2.9 ± 0.9minutes. Excluding eyes with comorbidities, logarithm of minimum angle of resolution BSCVA improved significantly from baseline preoperative values of 0.92 ± 0.58 to 0.02 ± 0.07 at 1 year (P < .001) and remained stable up to 3 years. Mean postoperative ECD decreased significantly (P < .001) from eye bank values to 1,818 ± 362, 1,675 ± 372, and 1,580 ± 423 cells/mm2 at 1, 2, and 3 years, respectively. No significant differences in ECD were observed between eyes with FECD and BK, but ECD was significantly lower in eyes with previous failed graft (P < .05). Three-year cumulative graft survival rate was significantly (P < .001) lower for eyes with previous failed graft (71%) than for FECD (97%) and BK (92%). Tri-folded endothelium-in DMEK requires minimal time for graft unfolding, which is the surgical step considered most challenging by corneal surgeons. Visual outcomes and complication rates are not adversely affected by the modification of the surgical technique.

Regenerative medicine in Fuchs' endothelial corneal dystrophy.

The management of Fuchs' endothelial corneal dystrophy (FECD) has evolved rapidly since the introduction of endothelial keratoplasty (EK). In recent years, advances in our understanding of endothelial cell biology, in particular with respect to the regenerative capacity of endothelial cells, have opened the door to novel therapeutic options that stray from the traditional paradigm of allograft transplantation. We review the development of descemetorhexis without EK (DWEK) as a primary treatment for FECD and discuss the lessons learned to date about the mechanism of wound healing, surgical technique, patient selection, and refractive outcomes. Multiple randomized clinical trials are currently underway to evaluate the potential for pharmacological supplementation with rho-associated kinase inhibitors to increase the success rate of corneal clearance following DWEK. Biologic supplementation with intracameral endothelial cell injection and acellular Descemet's membrane transplantation are other avenues of adjuvant therapy. DWEK is a promising surgical option for management of a subset of FECD patients.

Analyzing pre-symptomatic tissue to gain insights into the molecular and mechanistic origins of late-onset degenerative trinucleotide repeat disease

How genetic defects trigger the molecular changes that cause late-onset disease is important for understanding disease progression and therapeutic development. Fuchs’ endothelial corneal dystrophy (FECD) is an RNA-mediated disease caused by a trinucleotide CTG expansion in an intron within the TCF4 gene. The mutant intronic CUG RNA is present at one–two copies per cell, posing a challenge to understand how a rare RNA can cause disease. Late-onset FECD is a uniquely advantageous model for studying how RNA triggers disease because: (i) Affected tissue is routinely removed during surgery; (ii) The expanded CTG mutation is one of the most prevalent disease-causing mutations, making it possible to obtain pre-symptomatic tissue from eye bank donors to probe how gene expression changes precede disease; and (iii) The affected tissue is a homogeneous single cell monolayer, facilitating accurate transcriptome analysis. Here, we use RNA sequencing (RNAseq) to compare tissue from individuals who are pre-symptomatic (Pre_S) to tissue from patients with late stage FECD (FECD_REP). The abundance of mutant repeat intronic RNA in Pre_S and FECD_REP tissue is elevated due to increased half-life in a corneal cells. In Pre_S tissue, changes in splicing and extracellular matrix gene expression foreshadow the changes observed in advanced disease and predict the activation of the fibrosis pathway and immune system seen in late-stage patients. The absolute magnitude of splicing changes is similar in pre-symptomatic and late stage tissue. Our data identify gene candidates for early drivers of disease and biomarkers that may represent diagnostic and therapeutic targets for FECD. We conclude that changes in alternative splicing and gene expression are observable decades prior to the diagnosis of late-onset trinucleotide repeat disease.

Fuchs endothelial corneal dystrophy: The vicious cycle of Fuchs pathogenesis.

Fuchs endothelial corneal dystrophy (FECD) is the most common primary corneal endothelial dystrophy and the leading indication for corneal transplantation worldwide. FECD is characterized by the progressive decline of corneal endothelial cells (CECs) and the formation of extracellular matrix (ECM) excrescences in Descemet's membrane (DM), called guttae, that lead to corneal edema and loss of vision. FECD typically manifests in the fifth decades of life and has a greater incidence in women. FECD is a complex and heterogeneous genetic disease where interaction between genetic and environmental factors results in cellular apoptosis and aberrant ECM deposition. In this review, we will discuss a complex interplay of genetic, epigenetic, and exogenous factors in inciting oxidative stress, auto(mito)phagy, unfolded protein response, and mitochondrial dysfunction during CEC degeneration. Specifically, we explore the factors that influence cellular fate to undergo apoptosis, senescence, and endothelial-to-mesenchymal transition. These findings will highlight the importance of abnormal CEC-DM interactions in triggering the vicious cycle of FECD pathogenesis. We will also review clinical characteristics, diagnostic tools, and current medical and surgical management options for FECD patients. These new paradigms in FECD pathogenesis present an opportunity to develop novel therapeutics for the treatment of FECD.

Endothelial Cell Density Changes in the Corneal Center Versus Paracentral Areas After Descemet Membrane Endothelial Keratoplasty.

To analyze whether endothelial cell density (ECD) differs between central and paracentral areas after Descemet membrane endothelial keratoplasty (DMEK) and to identify the locations of the highest and lowest ECD. In this retrospective cohort study, central and paracentral ECDs of 30 eyes of 30 patients who underwent DMEK for Fuchs endothelial corneal dystrophy were evaluated. Central, superonasal, superotemporal, and inferior specular microscopic images were analyzed at 1, 3, 6, 9, and 12 months after DMEK. Changes in ECD by location and over time and changes in location for the highest and lowest ECD were evaluated. When compared with the preoperative donor ECD, the central ECD decreased by 32 (±11)% at 12 months postoperatively. ECD decline between 1 and 12 months postoperatively in the central, inferior, superonasal, and superotemporal location were 7%, 12%, 16%, and 13%, respectively (P < 0.0001 for all locations). Mean ECD was the highest in the center between the 3- to 12-month follow-up, whereas mean ECD was the lowest in the paracentral superonasal area at all time points (P < 0.001). Mean ECD of the highest and lowest density locations differed at all follow-up time points (P < 0.003). Postoperative ECD was not found to be uniform across the graft. Contrary to the density distribution in the normal endothelium, paracentral area ECDs were found to be consistently lower than in the central area. These differences were most prominent in the superonasal area and persisted 12 months postoperatively. Central ECD after DMEK might, thus, not represent an accurate proxy for cell density of the entire graft.

Descemet Membrane Endothelial Keratoplasty: Development of Contrast Sensitivity and Color Vision in Patients With Fuchs Endothelial Corneal Dystrophy.

To assess the developments in contrast sensitivity, color vision, and subjective perception after Descemet membrane endothelial keratoplasty (DMEK) in patients with Fuchs endothelial corneal dystrophy (FECD). Included in this study were pseudophakic, unilateral DMEK patients with bilateral FECD having a follow-up period of 6 months (n = 23). The mean age at surgery was 70 years (range: 52-81 years). Pseudophakic eyes without history of other ocular pathology or surgery served as a control (n = 10). Pelli-Robson contrast sensitivity and Panel-D15 color vision tests were used. Best-corrected visual acuity, modified visual functioning questionnaire-25, central corneal thickness, and endothelial cell density were assessed. We visualized the subjective impression of patients with bilateral FECD after unilateral DMEK in a subgroup using Photoshop CS6. Contrast sensitivity improved significantly from 1.35 ± 0.26 to 1.64 ± 0.17 (P = 0.002; control eyes: 1.92 ± 0.09). No difference in the color vision error score was observed for preoperative and postoperative eyes (P = 0.063). The best-corrected visual acuity improved significantly after surgery (P = 0.001). The average values in the Logarithm of the Minimum Angle of Resolution were 0.59 ± 0.42 preoperatively and 0.1 ± 0.10 postoperatively (control eyes: 0.01 ± 0.03). Examinations revealed a decrease of the central corneal thickness and endothelial cell density after surgery (P = 0.001; P = 0.001, respectively). Scores in the general and the driving questionnaire were significantly higher after surgery (P = 0.001; P = 0.005, respectively). This study showed significant improvement in subjective patient satisfaction and contrast sensitivity. Spontaneous subjective color vision improvement might be explained by significantly improved contrast sensitivity. Contrast sensitivity might be considered as a parameter in preoperative decision-making and evaluation of surgical outcome.

Chronology of cellular events related to mitochondrial burnout leading to cell death in Fuchs endothelial corneal dystrophy

Fuchs endothelial corneal dystrophy (FECD) is a degenerative eye disease characterized by corneal endothelial cell (CEC) death and the formation of guttae, an abnormal thickening of CEC’s basement membrane. At the tissue level, an oxidative stress causing mitochondrial damage and CEC death have been described to explain FECD pathogenesis. At the cellular level, our group has previously observed significant variability in the mitochondrial mass of FECD CECs. This led us to hypothesize that mitochondrial mass variability might play a key role in the chronology of events eventually leading to CEC death in FECD. We thus used different fluorescent markers to assess mitochondrial health and functionality as a function of mitochondrial mass in FECD corneal endothelial explants, namely, intra-mitochondrial calcium, mitochondrial membrane potential, oxidation level and apoptosis. This has led us to describe for the first time a sequence of events leading to what we referred to as a mitochondrial burnout, and which goes as follow. FECD CECs initially compensate for endothelial cell losses by incorporating mitochondrial calcium to help generating more ATP, but this leads to increased oxidation. CECs then resist the sustained need for more ATP by increasing their mitochondrial mass, mitochondrial calcium and mitochondrial membrane potential. At this stage, CECs reach their maximum capacity and start to cope with irreversible oxidative damage, which leads to mitochondrial burnout. This burnout is accompanied by a dissipation of the membrane potential and a release of mitochondrial calcium, which in turn leads to cell death by apoptosis.

Disease‐Causing Mutations Shift the pK of the pH‐Sensitive H+‐Conductor Slc4a11

SLC4A11 is a H+‐conducting membrane protein that is sensitive to changes in both intracellular and extracellular pH. It is expressed in corneal endothelial cells (CECs) where it functions alongside other acid/base transporters such as MCT1 and NBCe1. These proteins function to maintain the osmotic balance and clarity of the cornea. Mutations in SLC4A11 cause congenital hereditary endothelial dystrophy (CHED) and Fuchs’ endothelial corneal dystrophy (FECD). Signs of these corneal dystrophies include loss of normal CEC morphology and corneal edema. Previously—using the Xenopus oocyte expression system, two‐electrode voltage clamp circuitry (to monitor conductance), and H+‐selective microelectrodes (to monitor intracellular pH)—we determined that the intracellular pK of wild‐type (WT) mouse Slc4a11 activity is 7.15 ± 0.04 (n=13, SD, pHe=8.5). In this study we use the same experimental setup to explore whether disease‐causing mutations can affect the intracellular‐pH dependence (pK) of Slc4a11.We chose FECD mutation E399K and CHED mutations T401K and R804H for comparison to WT due to the loss or gain of a titratable residue. We find that Slc4a11‐‘E399K’ exhibits a pK value of 7.02 ± 0.03 (n = 6, SD) and that Slc4a11‐‘T401K’ exhibits a pK value of 7.09 ± 0.03 (n = 6, SD); both significantly acid‐shifted compared to WT. On the other hand, ‘R804H’‐Slc4a11 exhibits a significantly alkali‐shifted pK value of 7.29 ± 0.04 (n = 6, SD) [Statistics are the result of two‐tailed unpaired t‐tests with Bonferroni correction].Thus we describe three disease‐causing mutations that cause a shift in the intracellular pK value of Slc4a11. If the pH‐dependence of the H+ conductance mediated by Slc4a11 is critical to the physiological role of Slc4a11, these shifts in pK could contribute towards the etiology of corneal dystrophy.Support or Funding InformationThis work was supported by NIH R01‐EY028580 to MDP.