Selective endothelial removal: A case series of a phase I/II surgical trial with long-term follow up.

Peters anomaly is a congenital condition which results in a central corneal opacity from birth. Selective Endothelial Removal (SER) is a novel surgical technique and a form of regenerative therapy, which encourages clearance of the central corneal opacity by the patient's own corneal endothelial cells, and it may potentially be beneficial for the treatment of Peters anomaly. We have performed a phase I/II surgical trial, evaluating the safety of SER in four eyes (three patients) with Peters Anomaly. These patients underwent SER at between 9 and 39 months of age, each demonstrating clearance of central corneal opacities and improvements in vision post-operatively. No complications occurred in any of these eyes, at a minimal post-operative follow-up duration of 48 months. We conclude that SER for Peters anomaly is a safe surgical procedure. While encouraging efficacy outcomes have been observed, these findings should be further evaluated in a larger scale Phase II/III surgical trial.

New Therapies for Corneal Endothelial Diseases: 2020 and Beyond.

ABSTRACT: Penetrating keratoplasty used to be the only surgical technique for the treatment of end-stage corneal endothelial diseases. Improvements in surgical techniques over the past decade have now firmly established endothelial keratoplasty as a safe and effective modality for the treatment of corneal endothelial diseases. However, there is a worldwide shortage of corneal tissue, with more than 50% of the world having no access to cadaveric tissue. Cell injection therapy and tissue-engineered endothelial keratoplasty may potentially offer comparable results as endothelial keratoplasty while maximizing the use of cadaveric donor corneal tissue. Descemet stripping only, Descemet membrane transplantation, and selective endothelial removal are novel therapeutic modalities that take this a step further by relying on endogenous corneal endothelial cell regeneration, instead of allogenic corneal endothelial cell transfer. Gene therapy modalities, including antisense oligonucleotides and clustered regularly interspaced short palindromic repeats-based gene editing, offer the holy grail of potentially suppressing the phenotypic expression of genetically determined corneal endothelial diseases at the asymptomatic stage. We now stand at the crossroads of exciting developments in medical technologies that will likely revolutionize the way we treat corneal endothelial diseases over the next 2 decades.

BACILLARY LAYER DETACHMENT BECAUSE OF MACULAR NEOVASCULARIZATION.

PURPOSE: To describe the clinical and multimodal imaging features of bacillary layer detachment (BD), and its response to intravitreal anti-vascular endothelial growth factor therapy, in eyes with macular neovascularization. METHODS: Retrospective, observational case series of 14 eyes (14 patients, 7 men) imaged with eyes (14 patients, 7 men) were imaged with spectral-domain optical coherence tomography, and either fluorescein angiography or optical coherence tomography angiography. Therapeutic response was monitored with serial imaging and best-corrected visual acuity assessments. RESULTS: The mean age was 75 ± 13 (range: 45-96) years, with mean follow-up duration of 27 ± 21 (range: 1-56) months. Neovascular age-related macular degeneration was found in 71% (10/14) eyes. Type 2 macular neovascularization lesions were associated with BD in all 14 eyes. Subretinal hemorrhage was noted in 79% (11/14) eyes. BD promptly resolved after intravitreal antivascular endothelial growth factor therapy in all eyes. The baseline best-corrected visual acuity improved from logarithm of the minimum angle of resolution 0.84 ± 0.32 (Snellen equivalent 20/138) to logarithm of the minimum angle of resolution 0.48 ± 0.31 (Snellen equivalent 20/60) at the last follow-up, with treatment of the macular neovascularization. CONCLUSION: Type 2 macular neovascularization and subretinal hemorrhage are associated with BDs, which may be due to a rapid influx of exudative fluid into the potential space between the external limiting membrane and ellipsoid zone. Intravitreal antivascular endothelial growth factor therapy results in rapid resolution of BDs and visual improvement in most eyes.

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.

Regenerative capacity of the corneal transition zone for endothelial cell therapy.

The corneal endothelium located on the posterior corneal surface is responsible for regulating stromal hydration. This is contributed by a monolayer of corneal endothelial cells (CECs), which are metabolically active in a continuous fluid-coupled efflux of ions from the corneal stroma into the aqueous humor, preventing stromal over-hydration and preserving the orderly arrangement of stromal collagen fibrils, which is essential for corneal transparency. Mature CECs do not have regenerative capacity and cell loss due to aging and diseases results in irreversible stromal edema and a loss of corneal clarity. The current gold standard of treatment for this worldwide blindness caused by corneal endothelial failure is the corneal transplantation using cadaveric donor corneas. The top indication is Fuchs corneal endothelial dystrophy/degeneration, which represents 39% of all corneal transplants performed. However, the global shortage of transplantable donor corneas has restricted the treatment outcomes, hence instigating a need to research for alternative therapies. One such avenue is the CEC regeneration from endothelial progenitors, which have been identified in the peripheral endothelium and the adjacent transition zone. This review examines the evidence supporting the existence of endothelial progenitors in the posterior limbus and summarizes the existing knowledge on the microanatomy of the transitional zone. We give an overview of the isolation and ex vivo propagation of human endothelial progenitors in the transition zone, and their growth and differentiation capacity to the corneal endothelium. Transplanting these bioengineered constructs into in vivo models of corneal endothelial degeneration will prove the efficacy and viability, and the long-term maintenance of functional endothelium. This will develop a novel regenerative therapy for the management of corneal endothelial diseases.

Nrf2: A unifying transcription factor in the pathogenesis of Fuchs' endothelial corneal dystrophy.

Nuclear factor, erythroid 2 like 2 (Nrf2), is an oxidative stress induced transcription factor that regulates cytoprotective gene expression. Thus, Nrf2 is essential for cellular redox homeostasis. Loss or dysregulation of Nrf2 expression has been implicated in the pathogenesis of degenerative diseases, including diseases of the cornea. One of the most common diseases of the cornea in which Nrf2 is implicated is Fuchs' endothelial cornea dystrophy (FECD). FECD is the leading indication for corneal transplantation; and is associated with a loss of corneal endothelial cell (CEC) function. In this review, we propose that Nrf2 is an essential regulator of CEC function. Furthermore, we demonstrate that deficiency of Nrf2 function is a hallmark of FECD. In addition, we advocate that pharmacological targeting of Nrf2 as a possible therapy for FECD.

Intravitreal Injection with a Conjunctival Injection Device: A Single-Center Experience.

Purpose: To evaluate the clinical performance of the intravitreal injection assistant device (InVitria) compared with the conventional freehand technique for delivering intravitreal injections. Methods: Seventy patients were randomized to receive intravitreal injections via the conventional freehand technique while 70 received injections using the InVitria. Half of all procedures in each group were performed by junior surgeons, while the rest were performed by senior surgeons. Results: Mean injections times were 90.0 ± 23.3 seconds and 64.9 ± 26.8 seconds for conventional versus InVitria (P < 0.001). Mean injection times with the conventional technique were 85.5 ± 23.0 seconds vs. 94.2 ± 23.0 seconds for senior versus junior surgeons (P = 0.120). Mean injection times with the InVitria were 56.1 ± 26.1 seconds vs. 66.3 ± 26.9 seconds (P = 0.211) for senior versus junior surgeons. There were no significant differences in pain scores regardless of technique (conventional versus In Vitria: 2.03 ± 1.73 vs. 2.13 ± 2.20, P = 0.770). Conclusions: In our experience, the InVitria is a comparable alternative to the conventional freehand technique of delivering intravitreal injections, with the potential for faster injection times and without compromising on patient comfort. Translational Relevance: The study provides evidence to suggest that the InVitria may be deployed effectively in clinical practice.

Effects of Induced Astigmatism on Spectral Domain-OCT Angiography Quantitative Metrics.

PURPOSE: To analyze the effect of induced astigmatism on en-face spectral-domain optical coherence tomography angiography quantitative metrics. DESIGN: Prospective crossover study. METHODS: Normal eyes without astigmatism and with 0.75, 1.75, and 2.75 diopters (D) of with-the-rule (WTR) astigmatism were imaged using a 3 × 3-mm scan pattern SD-OCTA CIRRUS 5000 HD-OCT with AngioPlex (Carl Zeiss Meditec, Dublin, CA, USA). Quantitative parameters, including foveal avascular zone metrics, parafoveal vessel length density (VD), and perfusion density (PD) were corrected for magnification secondary to axial length and analyzed. Univariate linear regressions were performed within each eye to correlate quantitative metrics to the level of an induced astigmatic cylinder. RESULTS: Fifteen eyes from 15 patients were imaged. Every 1-D increase in induced WTR astigmatism was associated with a statistically significant decrease in VD and PD within all Early Treatment Diabetic Retinopathy Study inner ring quadrants; however, especially more so nasally (VD: 0.63; P < .001; PD: 0.0089; P = .001). For every 1-D increase in induced astigmatism, the resulting decrease in the inner ring superior quadrant was 12% greater for VD and 16% greater for PD versus that in the inferior quadrant. The resulting decrease in the inner ring nasal quadrant was 40% greater for VD and 48% greater for PD versus that in the temporal quadrant. CONCLUSIONS: Increasing levels of induced WTR astigmatism correlated with globally diminishing VD and PD, was more symmetrical for vertical than horizontal quadrants, and was most pronounced nasally. This may be due to a high prevalence of horizontally oriented vessels nasally and the horizontal optical defocus induced by WTR astigmatism.

Corneal dystrophies.

Corneal dystrophies are broadly defined as inherited disorders that affect any layer of the cornea and are usually progressive, bilateral conditions that do not have systemic effects. The 2015 International Classification of Corneal Dystrophies classifies corneal dystrophies into four classes: epithelial and subepithelial dystrophies, epithelial-stromal TGFBI dystrophies, stromal dystrophies and endothelial dystrophies. Whereas some corneal dystrophies may result in few or mild symptoms and morbidity throughout a patient's lifetime, others may progress and eventually result in substantial visual and ocular disturbances that require medical or surgical intervention. Corneal transplantation, either with full-thickness or partial-thickness donor tissue, may be indicated for patients with advanced corneal dystrophies. Although corneal transplantation techniques have improved considerably over the past two decades, these surgeries are still associated with postoperative risks of disease recurrence, graft failure and other complications that may result in blindness. In addition, a global shortage of cadaveric corneal graft tissue critically limits accessibility to corneal transplantation in some parts of the world. Ongoing advances in gene therapy, regenerative therapy and cell augmentation therapy may eventually result in the development of alternative, novel treatments for corneal dystrophies, which may substantially improve the quality of life of patients with these disorders.

Deep learning in estimating prevalence and systemic risk factors for diabetic retinopathy: a multi-ethnic study.

In any community, the key to understanding the burden of a specific condition is to conduct an epidemiological study. The deep learning system (DLS) recently showed promising diagnostic performance for diabetic retinopathy (DR). This study aims to use DLS as the grading tool, instead of human assessors, to determine the prevalence and the systemic cardiovascular risk factors for DR on fundus photographs, in patients with diabetes. This is a multi-ethnic (5 races), multi-site (8 datasets from Singapore, USA, Hong Kong, China and Australia), cross-sectional study involving 18,912 patients (n = 93,293 images). We compared these results and the time taken for DR assessment by DLS versus 17 human assessors - 10 retinal specialists/ophthalmologists and 7 professional graders). The estimation of DR prevalence between DLS and human assessors is comparable for any DR, referable DR and vision-threatening DR (VTDR) (Human assessors: 15.9, 6.5% and 4.1%; DLS: 16.1%, 6.4%, 3.7%). Both assessment methods identified similar risk factors (with comparable AUCs), including younger age, longer diabetes duration, increased HbA1c and systolic blood pressure, for any DR, referable DR and VTDR (p > 0.05). The total time taken for DLS to evaluate DR from 93,293 fundus photographs was ~1 month compared to 2 years for human assessors. In conclusion, the prevalence and systemic risk factors for DR in multi-ethnic population could be determined accurately using a DLS, in significantly less time than human assessors. This study highlights the potential use of AI for future epidemiology or clinical trials for DR grading in the global communities.

The future of keratoplasty: cell-based therapy, regenerative medicine, bioengineering keratoplasty, gene therapy.

PURPOSE OF REVIEW: To provide an update on the state of development of novel therapeutic modalities for the treatment of corneal diseases. RECENT FINDINGS: Novel corneal therapeutics may be broadly classified as cell therapy, regenerative medicine, bioengineered corneal grafts and gene therapy. Cell therapy encompasses cultivation of cells, such as corneal endothelial cells (CECs) and keratocytes to replenish the depleted native cell population. Regenerative medicine is mainly applicable to the corneal endothelium, and is dependent on the ability of native, healthy CECs to restore the corneal endothelium following trauma or descemetorhexis; this approach may be effective for the treatment of Peter's anomaly and Fuchs endothelial corneal dystrophy (FECD). Bioengineered corneal grafts are synthetic constructs designed to replace cadaveric corneal grafts; tissue-engineered endothelial-keratoplasty grafts and bioengineered stromal grafts have been experimented in animal models with favourable results. Gene therapy with antisense oligonucleotide and CRISPR endonucleases, including deactivated Cas9, may potentially be used to treat FECD and TGFBI-related corneal dystrophies. SUMMARY: These novel therapeutic modalities may potentially supersede keratoplasty as the standard of care in the future.

Trinucleotide repeat expansion length as a predictor of the clinical progression of Fuchs' Endothelial Corneal Dystrophy.

PURPOSE: To determine if CTG18.1 TNR expansion length prognosticates the clinical progression of Fuchs' Endothelial Corneal Dystrophy (FECD). METHODS: This was a prospective cohort study. A total of 51 patients with newly diagnosed FECD were recruited and followed-up over a period of 12 years, from November 2004 to April 2016. Baseline clinical measurements included central corneal thickness (CCT), endothelial cell density (ECD) and CTG18.1 TNR expansion length from peripheral leukocytes, with yearly repeat measurements of CCT and ECD. A patient was defined to have experienced significant clinical progression and to have developed Threshold Disease if any of these criteria were fulfilled in either eye: a) CCT increased to >700µm, b) ECD decreased to <700 cells/mm2, or c) underwent keratoplasty for treatment of FECD. RESULTS: Patients were categorized as having at least one allele whose maximum allele length was equal to or greater than 40 repeats (L≥40, n = 22, 43.1%), or having both alleles shorter than 40 repeats (L<40). Threshold Disease rates at the 5-year time point were 87.5% for the L≥40 group and 47.8% for the L<40 group (p = 0.012). This difference narrowed and was no longer statistically significant at the 8-years (92.9% vs 78.9%, p = 0.278) and 10-years (92.9% vs 84.2%, p = 0.426) time points. CONCLUSIONS: L≥40 patients are at greater risk of FECD progression and development of Threshold Disease within the first 5 years following diagnosis.

Regenerative Therapy for Fuchs Endothelial Corneal Dystrophy.

PURPOSE: Fuchs endothelial corneal dystrophy (FECD) is an acquired corneal endotheliopathy and is one of the most common indications for corneal transplantation surgery worldwide. Endothelial keratoplasty (EK) is the most popular form of corneal transplantation for FECD. In standard EK surgery, the patient's corneal endothelium and basement membrane [ie, Descemet membrane (DM)] are first removed, followed by transplantation of donor tissue that comprises allogenic corneal endothelial cells, DM, and corneal stroma of variable thickness. We hypothesized that in lieu of EK, transplantation of acellular DM (ie, Descemet membrane transplantation, DMT) may similarly restore anatomical and functional integrity of the corneal endothelium, by stimulating centripetal migration of peripheral host corneal endothelial cells. METHODS: A case report of a first-in-human trial of DMT for treatment of FECD is presented. RESULTS: A patient with FECD was successfully treated with DMT. Her preoperative best-corrected Snellen visual acuity (BCVA) was 6/18, central corneal thickness was 603 nm, and central corneal endothelial cell density was unrecordable. By postoperative month 6, her best-corrected Snellen visual acuity had improved to 6/7.5, central corneal thickness was 569 nm, and central corneal endothelial cell density was 889 cells/mm. She remained stable despite complete cessation of all medications including immunosuppressants. No significant postoperative complications have been encountered. CONCLUSIONS: DMT may be effective for treatment of FECD. Achievement of endothelial regeneration without allogenic corneal endothelial cell transplantation and exposure to the attendant risks of graft rejection and chronic immunosuppression represents a significant improvement from the current paradigm of EK.

Selective Endothelial Removal for Peters Anomaly.

PURPOSE: Peters anomaly is the most common cause of congenital corneal opacities. Although conservative management is often ineffective except in mild cases, surgical intervention in the form of penetrating keratoplasty is fraught with unpredictability and often has unacceptable postoperative outcomes. As such, there is a need to explore alternative surgical interventions that may possibly improve the postoperative visual prognosis in these patients. In this report, we present a case of type 1 Peters anomaly treated by selective endothelial removal without corneal tissue transplantation. METHODS: A case report with literature review. RESULTS: A 21-month-old child, who presented with unilateral type 1 Peters anomaly, underwent selective endothelial removal without corneal tissue transplantation for the treatment of her condition. The patient demonstrated excellent anatomical and visual recovery after the procedure over a 1-year period. Her visual acuity had improved from 20/960 preoperatively to 20/30 during the latest review. Postoperative recovery was not complicated by the development of any sight-threatening complications, and she has been successfully weaned off all topical and systemic medications. CONCLUSIONS: Selective endothelial removal can potentially be used to treat cases of type 1 Peters anomaly.

Evolving therapies for Fuchs' endothelial dystrophy.

Fuchs' endothelial dystrophy (FED) is characterized by corneal endothelial dysfunction and guttate excrescences on the posterior corneal surface, and is the leading indication for corneal transplantation in developed countries. In severe cases, keratoplasty is considered as the gold standard of treatment. However, there have been significant developments in our understanding of FED over the past decade. Attempts have been made to treat this disease with regenerative therapy techniques such as primary descemetorhexis without an endothelial graft or with a tissue-engineering approach. The discovery of a strong association between the CTG18.1 trinucleotide repeat expansion sequence and FED may pave the way for gene therapy strategies in the future. In this review, we evaluate these novel therapeutic modalities as possible alternatives to keratoplasty as the standard of care for FED.

Corneal lenticule storage before reimplantation.

Purpose: To explore the optimal lenticule storage conditions that maintain lenticule integrity and clarity. Methods: A total of 99 lenticules obtained from myopic patients undergoing small incision lenticule extraction (SMILE) were divided into four combinations for short-term storage conditions: PBS, Dulbecco's Modified Eagle's Medium (DMEM), Optisol GS, or anhydrous glycerol. Two thirds of the lenticules were further stored for 4 weeks under eight different conditions. Clarity evaluation with transmittance measurements, cell-death assays with terminal deoxynucleotidyl transferase-mediated nick end labeling assay (TUNEL), collagen fibril spacing and necrotic response assessed with transmission electron microscopy (TEM), and immunohistochemistry analysis for human leukocyte antigens (HLAs) and CD45 for immunogenicity, and matrix metalloproteinase (MMP)-2 for keratocyte response, were undertaken at baseline, 48 h (short term), and 4 weeks (long term). Results: The TUNEL and immunogenicity results were comparable among the groups. The mean percentage of TUNEL-positive cells across all groups was 24.3% ± 11.8% and 62.9% ± 20.7% at the 48 h and 4 week time points, respectively. HLA-ABC+, HLA-DR+, and CD45+ cells were extremely rare, and MMP-2 expression ranged from non-detectable to minimal, under all conditions at all time points. Transmittance at 4 weeks was significantly different among groups with the greatest maintenance of clarity seen in the lenticules stored initially in DMEM at 4 °C for 48 h followed by cryopreservation in serum-free medium or glycerol at 4 °C followed by storage at room temperature. At TEM analysis at 4 weeks, the lenticules cryopreserved in liquid nitrogen, regardless of storage solutions, had significantly narrower inter-fibrillar distance than controls, while glycerol-preserved lenticules, at either room temperature or -80 °C, maintained the inter-fibrillar distance. Conclusions: Clarity, structural integrity, and low immunogenicity under various conditions, at 4 °C or room temperature for short-term storage, offer encouragement for lenticule storage. It can be undertaken without access to s specialized and potentially expensive laboratory setup at least within the first 48 h before transportation to larger facilities for long-term storage.

Improving the rates of electronic results acknowledgement at a tertiary eye care centre.

BACKGROUND: Hundreds of thousands of tests are performed annually in hospitals worldwide. Safety Issues arise when abnormal results are not recognized promptly resulting in delayed treatment and increased morbidity and mortality. As a result Singapore's largest healthcare group, Singhealth introduced an electronic result acknowledgement system. This system was adopted by the Singapore National Eye Centre (SNEC) in February 2016. Baseline measurements show that weekly numbers of unacknowledged results ranged from 193 to 617. The current standards of electronic results acknowledgement posts a significant patient safety hazard. METHODS: Root cause analysis was performed to identify contributory factors. Pareto principle was then used by the authors to identify the main contributory factors. We employed the rapid cycle improvement Plan-do-study-act (PDSA) strategy to test and evaluate implemented changes. Changes are implemented for 2 weeks and data collected prospectively. The data is analyzed the week after and the following PDSA actions are decided and instituted the following week. 3 PDSA cycles were undertaken in total. RESULTS: The first PDSA cycle focused on raising awareness of the problem at hand, the number of unacknowledged results drastically decreased during the 1stweek of implementation of our PDSA from 617 to 254. The second PDSA cycle targeted the lack of knowledge of doctors involved in the electronic result acknowledgement process. There was a trend downwards near the end of the cycle which continued through the week after. The third PDSA cycle targeted individual doctors and provided individual remedial training. Second line doctors were also equipped to better handle abnormal results. There was significant improvement with the number of unacknowledged abnormal results dropping to <5 a week. CONCLUSIONS: Multiple factors were identified to contribute to the low compliance to electronic acknowledgement of results. The role doctors play in the issue at hand was paramount and required careful handling in a professional manner with multiple reminders and emphasis on the importance of acknowledging and acting on the results.A significant improvement in the rates of acknowledgement of abnormal results was demonstrated with clear benefits to patient safety. Interventions can be replicated when implementing similar systems to other areas of healthcare.