Update on the Surgical Management of Fuchs Endothelial Corneal Dystrophy

The Role of Rho Kinase Inhibitors in Corneal Diseases

The cornea, as the outermost layer of the eye, plays a crucial role in vision by focusing light onto the retina. Various diseases and injuries can compromise its clarity, leading to impaired vision. This review aims to provide a thorough overview of the pharmacological properties, therapeutic potential and associated risks of Rho-associated protein kinase (ROCK) inhibitors in the management of corneal diseases. The article focuses on four key ROCK inhibitors: Y-27632, fasudil, ripasudil, and netarsudil, providing a comparative examination. Studies supporting the use of ROCK inhibitors highlight their efficacy across diverse corneal conditions. In Fuchs' endothelial corneal dystrophy, studies on the application of Y-27632, ripasudil, and netarsudil demonstrated noteworthy enhancements in corneal clarity, endothelial cell density, and visual acuity. In pseudophakic bullous keratopathy, the injection of Y-27632 together with cultured corneal endothelial cells into the anterior chamber lead to enhanced corneal endothelial cell density and improved visual acuity. Animal models simulating chemical injury to the cornea showed a reduction of neovascularization and epithelial defects after application of fasudil and in a case of iridocorneal endothelial syndrome netarsudil improved corneal edema. Addressing safety considerations, netarsudil and ripasudil, both clinically approved, exhibit adverse events such as conjunctival hyperemia, conjunctival hemorrhage, cornea verticillata, conjunctivitis, and blepharitis. Monitoring patients during treatment becomes crucial to balancing the potential therapeutic benefits with these associated risks. In conclusion, ROCK inhibitors, particularly netarsudil and ripasudil, offer promise in managing corneal diseases. The comparative analysis of their pharmacological properties and studies supporting their efficacy underscore their potential therapeutic significance. However, ongoing research is paramount to comprehensively understand their safety profiles and long-term outcomes in diverse corneal conditions, guiding their optimal application in clinical practice.

Association Between Fuchs Endothelial Corneal Dystrophy, Diabetes Mellitus, and Multimorbidity

PURPOSE

The aim of this study was to assess risk for demographic variables and other health conditions that are associated with Fuchs endothelial corneal dystrophy (FECD).

METHODS

We developed a FECD case-control algorithm based on structured electronic health record data and confirmed accuracy by individual review of charts at 3 Veterans Affairs (VA) Medical Centers. This algorithm was applied to the Department of VA Million Veteran Program cohort from whom sex, genetic ancestry, comorbidities, diagnostic phecodes, and laboratory values were extracted. Single-variable and multiple variable logistic regression models were used to determine the association of these risk factors with FECD diagnosis.

RESULTS

Being a FECD case was associated with female sex, European genetic ancestry, and a greater number of comorbidities. Of 1417 diagnostic phecodes evaluated, 213 had a significant association with FECD, falling in both ocular and nonocular conditions, including diabetes mellitus (DM). Five of 69 laboratory values were associated with FECD, with the direction of change for 4 being consistent with DM. Insulin dependency and type 1 DM raised risk to a greater degree than type 2 DM, like other microvascular diabetic complications.

CONCLUSIONS

Female sex, European ancestry, and multimorbidity increased FECD risk. Endocrine/metabolic clinic encounter codes and altered patterns of laboratory values support DM increasing FECD risk. Our results evoke a threshold model in which the FECD phenotype is intensified by DM and potentially other health conditions that alter corneal physiology. Further studies to better understand the relationship between FECD and DM are indicated and may help identify opportunities for slowing FECD progression.

Shotgun proteomics identification of proteins expressed in the Descemet's membrane of patients with Fuchs endothelial corneal dystrophy

Fuchs endothelial corneal dystrophy (FECD) is a slowly evolving, bilateral disease of the corneal endothelium, characterized by an abnormal accumulation of extracellular matrix (ECM) in the basement membrane (Descemet's membrane, DM). This results in the formation of small round excrescences, called guttae, and a progressive disappearance of endothelial cells. In the intermediate stage, the numerous guttae create significant optical aberrations, and in the late stage, the loss of endothelial function leads to permanent corneal edema. The molecular components of guttae have not been fully elucidated. In the current study, we conducted shotgun proteomics of the DMs, including guttae, obtained from patients with FECD and revealed that 32 proteins were expressed only in the FECD-DMs but not in the DMs of control subjects. Subsequent enrichment analyses identified associations with multiple ECM-related pathways. Immunostaining of flat-mounted DMs confirmed that 4 of the top 5 identified proteins (hemoglobin α, SRPX2, tenascin-C, and hemoglobin γδεβ) were expressed in FECD-DMs but not in non-FECD-DMs. Fibrinogen α was strongly expressed in FECD-DMs, but weakly expressed in non-FECD-DMs. We also demonstrated that matrix-assisted laser desorption ionization imaging mass spectrometry (MALDI-IMS) can display the in situ spatial distribution of biomolecules expressed in the DM, including the guttae.

Unintentional Descemet Cleft Introduces Novel Mechanism of Maintenance of Corneal Clarity

PURPOSE

The purpose of this study was to report a case of corneal transparency for 7 months after the formation and persistence of a Descemet fluid cleft.

METHODS

We report the case of a 64-year-old woman undergoing anterior chamber reformation 2 months after Baerveldt implantation of the right eye. During the procedure, the ophthalmic viscoelastic was inadvertently injected into the posterior stroma, nearly isolating the corneal endothelial cell layer, and creating a Descemet fluid cleft filled with viscoelastic. The patient was managed conservatively and monitored near monthly for corneal decompensation.

RESULTS

The cornea remained centrally clear for 207 days after the initial anterior chamber reformation until the collapse of the viscoelastic cleft. When the cleft completely collapsed, the cornea became diffusely edematous, and the patient underwent cataract removal and intraocular lens placement without need for Descemet stripping endothelial keratoplasty to maintain vision. During these 7 months, the patient's best-corrected visual acuity remained stable at 20/25 +2 or better. Intraocular pressure was also stable, averaging 18.2 mm Hg.

CONCLUSIONS

We hypothesize that corneal transparency can be maintained in the absence of endothelial cell function provided that aqueous humor cannot reach the cornea and disrupt the arrangement of the interfibrillar space.

Evaluating Keratoplasty for Fuchs' Endothelial Corneal Dystrophy: A Literature Review

Fuchs' endothelial corneal dystrophy (FECD) is progressive corneal endothelium dysfunction, characterised by corneal oedema, and potential blindness if left untreated. Keratoplasty is the only definitive treatment to restore vision in FECD, with different surgical techniques being described. The corneal transplant has been described as the most commonly performed and most successful allogenic transplant globally; therefore, it is crucial to dissect it further since a large proportion of the population worldwide is likely to be impacted. We feel that an updated literature review is both very relevant and necessary at present and aim to amalgamate more recent data on the topic (including meta-analyses, systematic reviews, and randomised control trials (RCTs), among others). We acknowledge that the paucity of reliable data limits progress for FECD and that there are existing ethical complexities in performing prospective trials on patients.  Traditionally, the surgery for FECD was limited to penetrating keratoplasty (PK), yet recent developments have introduced more advanced procedures and adapted the existing ones, to provide treatment specific to the disease-affected corneal layers. The questions we will address encompass: how does the severity of FECD govern the treatment options available, what are the differences between PK and types of endothelial keratoplasty (EK), what are the expected clinical outcomes of each of these operations, what are the potential concerns with the idealistic descemetorhexis surgery, and what do we envisage for times to come? Besides this, novel minimally-invasive pharmacological techniques are now being trialled, such as Rho kinase (ROCK) inhibition and cultured endothelial cells (CECs), which may drastically improve the dependence on corneal donors. We examine and critically appraise the literature to explore the understanding of FECD, and the treatment options that exist: historically, currently, and those anticipated for the future.

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

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

Experimental Oxidative Stress Breaks Down the Barrier Function of the Corneal Endothelium

Purpose: The fluid pump and barrier functions of the corneal endothelium maintain stromal deturgescence required for corneal transparency. The effect of oxidative stress, a hallmark of Fuchs endothelial corneal dystrophy (FECD), on the endothelial barrier function has been investigated. Methods: The endothelium of porcine corneas ex vivo was exposed to (1) membrane permeable oxidants (H₂O₂, 100 μM, 1 h; tert-butyl-hydroperoxide, 100 μM, 1 h), or (2) ultraviolet A (UVA) with photosensitizers for 15 min, riboflavin (50 μM) or tryptophan (Trp) (100 μM). The effects on the apical junction complex were analyzed by (1) immunostaining the perijunctional actomyosin ring (PAMR) and ZO-1 and (2) assessment of paracellular flux of fluorescein isothiocyanate (FITC)-avidin across cultured endothelial cells grown on biotinylated-gelatin film. The extent of oxidative stress was quantified by changes in intracellular reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) in addition to lipid peroxidation and release of lactate dehydrogenase (LDH). Results: Both methods of oxidative stress led to the disruption of PAMR and ZO-1 concurrent with changes in ROS levels, depolarization of MMP, increased lipid peroxidation, elevated LDH release, and increased permeability of FITC-avidin. The effects of direct oxidants were opposed by SB-203580 [p38 mitogen-activating protein (MAP) kinase inhibitor; 10 μM]. The damage by UVA+photosensitizers was blocked by extracellular catalase (10,000 U/mL). Conclusions: (1) Acute oxidative stress breaks down the barrier function through destruction of PAMR in a p38 MAP kinase-dependent manner. (2) UVA+photosensitizers elicit the breakdown of PAMR via type I reactions, involving H₂O₂ release. (3) Blocking the oxidative stress prevents loss of barrier function, which could be helpful in the therapeutics of FECD.

Descemetorhexis Without Endothelial Keratoplasty in Fuchs Endothelial Corneal Dystrophy: A Systematic Review and Meta-Analysis

PURPOSE

Descemetorhexis without endothelial keratoplasty (DWEK) is an innovative corneal intervention and potentially effective against Fuchs endothelial corneal dystrophy (FECD). We aimed to conduct a systematic review and meta-analysis on the outcomes of DWEK, associated or not with phacoemulsification (PKE) and rho-kinase inhibitor (RHOKI) in FECD.

METHOD

PubMed, Cochrane Library, Embase, ClinicalTrials.gov , and Science Direct were searched for studies until November 29, 2020. We performed random-effects meta-analyses and meta-regressions, stratified by the type of intervention and descemetorhexis size (PROSPERO CRD42020167566).

RESULTS

We included 11 articles (mainly case series, both prospective and retrospective), representing 127 eyes of 118 patients. DWEK globally improved visual acuity (effect size = -1.11, 95% confidence interval, -1.70 to -0.52, P < 0.001) and pachymetry (-1.25, -1.92 to -0.57, P < 0.001), without significant effects on endothelial cell count (-0.59, -2.00 to 0.83, P = 0.419). The 3 types of interventions (ie, DWEK ± RHOKI, DWEK ± PKE, and DWEK ± PKE ± RHOKI) improved visual acuity and pachymetry in FECD. A descemetorhexis size ≤4 mm improved visual acuity (-0.72, -1.29 to -0.14, P < 0.001) and pachymetry (-0.68, -0.98 to -0.38, P < 0.001), whereas >4 mm did not. Overall, DWEK failure (ie, the prevalence of EK after DWEK) was 17% (7%-27%, P < 0.001), with 4% (0%-8%, P = 0.08) for a descemetorhexis size ≤4 mm.

CONCLUSIONS

Despite the lack of comparative studies, DWEK seemed to improve visual acuity and pachymetry in early stages of FECD. A descemetorhexis size ≤4 mm was associated with the best visual outcomes and pachymetry.

Assessment of the Quality and Reliability of YouTube Videos on Fuchs Endothelial Corneal Dystrophy

Objectives

The aim of the study was to assess the quality and reliability of videos on Fuchs endothelial corneal dystrophy (FECD) on YouTube.

Methods

A search of YouTube was performed for the term "FECD" without any changes to the website's standard search preferences. The first 100 videos were recorded. A total of 71 videos were evaluated regarding the DISCERN score (min-max: 16-75), Journal of the American Medical Association (JAMA) score (min-max: 0-4), and Global Quality Scale (GQS) score (min-max: 0-5).

Results

The mean DISCERN score was 40.1±15.6 (moderate), the mean JAMA score was 2.01±0.7 (poor), the mean GQS score was 2.5±1.3 (moderate), and the mean video power index score was 106.8±135.7. Twenty-three of the videos (32.4%) were uploaded by physicians, 25 (35.2%) by universities/private hospitals, and 21 (29.6%) by health channels. Thirty-six videos (50.7%) contained information about the disease, 24 (33.8%) discussed surgical techniques, and 11 (15.5%) were about patient experience.

Conclusion

YouTube provides only moderate-quality health information on FECD. Physicians and professional organizations should be aware of and embrace this evolving technology to raise awareness about FECD.

Cost Burden of Endothelial Keratoplasty in Fuchs Endothelial Dystrophy: Real-World Analysis of a Commercially Insured US Population (2014–2019)

Purpose

To assess the incremental burden of corneal transplant surgery for US commercially insured patients with Fuchs endothelial corneal dystrophy (FECD) treated with endothelial keratoplasty (EK) compared to controls.

Methods

The study design was retrospective cohort using IBM^® MarketScan^® claims (January 2014–September 2019) and included EK-treated (N=1562) and control patients (N=23,485) having ≥12 months’ enrollment before and after diagnosis, who were subsequently matched on select characteristics. The index date was the beginning of the pre-operative period (3 months before EK); synthetic EK index was assigned for controls. All-cause, eye-disease, and complication-related healthcare resource utilization (HCRU) and costs were compared up to 36 months post index. For a small subset of patients, patient data were linked to the Health and Productivity Management supplemental database, which integrates data on productivity loss and disability payments.

Results

Matched cohorts included 804 EK-treated and 1453 controls with average age 65.7 years, 1383 (61%) female. Over 12 months of follow-up, all-cause ($41,199 vs $20,222, p<0.001) and eye-disease related costs ($22,951 vs $1389, p<0.001) were higher among EK-treated patients than controls. The cost differential increased additionally by $1000–$2000 per annum by 36 months of follow-up. While balanced at baseline, over follow-up EK-treated patients had higher prevalence of glaucoma, elevated intraocular pressure, cataract, cataract surgery, diagnosis of cornea transplant rejection, retinal edema. By 36 month of follow-up, EK-treated patients had 9 more short-term disability days, resulting in $2992 additional burden of disability payments.

Conclusion

This study found a higher cost burden among FECD patients receiving EK treatment versus those who did not. With a shift in management of FECD, cost burden estimates generated in this study could serve as an important benchmark for future studies.

Endophthalmitis secondary to donor to host infection in posterior lamellar keratoplasties: A systematic review

Donor to host transmission of infectious agents is a well-recognized entity, more commonly related to Endothelial Keratoplasty (EK) than to Penetrating Keratoplasty (PK), that involves complications ranging from interface keratitis to endophthalmitis. A systematic review of the literature was conducted to identify the published articles until December 2020 reporting cases of endophthalmitis secondary to corneal graft contamination in posterior lamellar keratoplasties (DSAEK and DMEK) along with donor characteristics, microbiological profile, treatment and outcomes. Each identified article was assessed to meet donor to host infection criteria, defined as a post-procedural infection in which the same microbiological agent was identified in both the donor corneoscleral rim or preservation medium and receptor ocular tissue. From 23 research articles, eight reports of endophthalmitis in nine patients following DSAEK or DMEK secondary to donor to host infection fulfilled the inclusion criteria. The majority were male and the median age was 72.0 (45.0-81.0) years old. Indications of surgery were primarily pseudophakic bullous keratopathy and Fuchs dystrophy. A fungal pathogen was identified in eight of nine patients. All the cases underwent surgical management with lenticule removal or endothelial plaque aspiration. The final corrected distance visual acuity (CDVA) in all cases was 20/200 or better. Endophthalmitis after an EK procedure is a rare complication whose outcome depends on the aggressive and precocious treatment. Identification of early signs of interface keratitis and lenticule removal seems mandatory in patients undergoing DSAEK or DMEK to prevent further involvement of the globe.

Descemet Stripping Only for Fuchs Endothelial Corneal Dystrophy: Will It Become the Gold Standard?

ABSTRACT

Descemet stripping only (DSO) has become a viable treatment option for certain cases of Fuchs Endothelial Corneal Dystrophy (FECD). This article describes the history of the development of DSO, its current status, and what successful DSO tells us about the pathophysiology of FECD. Remaining questions and future directions are also highlighted.

To compare corneal confocal microscopy of eyes with Fuchs' endothelial corneal dystrophy after two different endothelial surgeries

PURPOSE

To study the features of corneal confocal microscopy of eyes with Fuchs' endothelial corneal dystrophy (FECD) after successful Descemet stripping automated endothelial keratoplasty (DSAEK) versus Descemet membrane endothelial keratoplasty (DMEK).

METHODS

Thirty-two eyes affected by FECD with corneal oedema requiring a corneal graft were treated with DSAEK (15 eyes) or DMEK (17 eyes). All patients underwent in vivo corneal confocal microscopy (IVCCM) at 6 months postoperatively. We evaluated preoperative and postoperative corrected distance visual acuity (CDVA) and the correlation with IVCCM characteristics.

RESULTS

Using IVCCM, Z-scan curve analysis showed similar subepithelial reflectivity peaks between the two groups (DSAEK 1256 SU ± 514 vs DMEK 1118 SU ± 408, p = 0.411), while the interface reflectivity was significantly higher in the DMEK group (1511 SU ± 357) than in the DSAEK group (1029 SU ± 413, p = 0.002).

CONCLUSION

Comparing the corneal confocal microscopic characteristics after DMEK with those after DSAEK and their correlation with visual outcome at 6 months, we hypothesized that the presence of a third reflectivity peak in the Z-scan curves of DSAEK patients could justify the poorer visual outcome with this endothelial surgery than with DMEK.

Potential Functional Restoration of Corneal Endothelial Cells in Fuchs Endothelial Corneal Dystrophy by ROCK Inhibitor (Ripasudil)

PURPOSE

Rho-associated kinase (ROCK) inhibitors have been successfully used as a rescue strategy in eyes that failed to clear after descemetorhexis without endothelial graft for treatment of Fuchs endothelial corneal dystrophy (FECD). The functional mechanisms by which ROCK inhibitors modulate corneal endothelial cell regeneration in FECD patients have, however, not been clarified. Here, we analyzed the effect of the ROCK inhibitor ripasudil on corneal endothelial cells of FECD patients and normal donors using ex vivo tissue and in vitro cellular models.

DESIGN

Experimental study: laboratory investigation.

METHODS

This institutional study used endothelial cell-Descemet membrane lamellae from FECD patients (n = 450) undergoing Descemet membrane endothelial keratoplasty (FECD ex vivo model), normal research-grade donor corneas (n = 30) after scraping off central endothelial cells (ex vivo wound healing model), normal donor corneas (n = 20) without endothelial injury, and immortalized cell lines (n = 3) generated from FECD patients (FECD in vitro model). Descemet membrane lamellae were dissected into halves and incubated for 24-72 hours in storage medium with or without a single dose of 30 μM ripasudil. The effects of ripasudil on expression of genes and proteins related to endothelial cell proliferation, migration, functionality, and endothelial-to-mesenchymal transition were analyzed and complemented by functional assays on FECD cell lines.

RESULTS

A single dose of ripasudil induced significant upregulation of genes and proteins related to cell cycle progression, cell-matrix adhesion and migration, as well as endothelial barrier and pump function up to 72 hours, whereas classical markers of endothelial-to-mesenchymal transition were downregulated in both FECD and normal specimens compared to unstimulated controls ex vivo. In addition to stimulation of proliferation and migration, ripasudil-induced changes in expression of functional signature genes could be also verified in FECD cell lines in vitro.

CONCLUSIONS

These data support the concept that inhibition of ROCK signaling represents a potent tool in regenerative therapies in FECD patients through reactivation of cell proliferation and migration as well as restoration of endothelial pump and barrier function without inducing adverse phenotypic changes.