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1.
The Role of Vitamin A in Retinal Diseases.
Sajovic, J, Meglič, A, Glavač, D, Markelj, Š, Hawlina, M, Fakin, A
International journal of molecular sciences. 2022;(3)
Abstract
Vitamin A is an essential fat-soluble vitamin that occurs in various chemical forms. It is essential for several physiological processes. Either hyper- or hypovitaminosis can be harmful. One of the most important vitamin A functions is its involvement in visual phototransduction, where it serves as the crucial part of photopigment, the first molecule in the process of transforming photons of light into electrical signals. In this process, large quantities of vitamin A in the form of 11-cis-retinal are being isomerized to all-trans-retinal and then quickly recycled back to 11-cis-retinal. Complex machinery of transporters and enzymes is involved in this process (i.e., the visual cycle). Any fault in the machinery may not only reduce the efficiency of visual detection but also cause the accumulation of toxic chemicals in the retina. This review provides a comprehensive overview of diseases that are directly or indirectly connected with vitamin A pathways in the retina. It includes the pathophysiological background and clinical presentation of each disease and summarizes the already existing therapeutic and prospective interventions.
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2.
The gut microbiota in retinal diseases.
Bringer, MA, Gabrielle, PH, Bron, AM, Creuzot-Garcher, C, Acar, N
Experimental eye research. 2022;:108867
Abstract
The gut microbiota is a complex ecosystem that inhabits the gastrointestinal tract and consists of archaea, fungi, viruses, and bacteria, with bacteria being dominant. From birth onwards, it coevolves dynamically together with the host. The composition of the gut microbiota is under the influence of a complex interplay between both host and environmental factors. Scientific advances in the past few decades have shown that it is essential in maintaining homeostasis and tipping the balance between health and disease. In addition to its role in food digestion, the gut microbiota is implicated in regulating multiple physiological processes in the host gut mucosa and in distant organs such as the brain. Persistent imbalance between gut microbial communities, termed "dysbiosis," has been associated with several inflammatory and metabolic diseases as well as with central nervous system disorders. In this review, we present the state of the art of current knowledge on an emerging concept, the microbiota-retina axis, and the potential role of its disturbance in the development of retinopathies. We also describe several microbiota-targeting strategies that could constitute preventive and therapeutic tools for retinopathies.
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A MULTITASK DEEP-LEARNING SYSTEM FOR ASSESSMENT OF DIABETIC MACULAR ISCHEMIA ON OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY IMAGES.
Yang, D, Sun, Z, Shi, J, Ran, A, Tang, F, Tang, Z, Lok, J, Szeto, S, Chan, J, Yip, F, et al
Retina (Philadelphia, Pa.). 2022;(1):184-194
Abstract
PURPOSE We aimed to develop and test a deep-learning system to perform image quality and diabetic macular ischemia (DMI) assessment on optical coherence tomography angiography (OCTA) images. METHODS This study included 7,194 OCTA images with diabetes mellitus for training and primary validation and 960 images from three independent data sets for external testing. A trinary classification for image quality assessment and the presence or absence of DMI for DMI assessment were labeled on all OCTA images. Two DenseNet-161 models were built for both tasks for OCTA images of superficial and deep capillary plexuses, respectively. External testing was performed on three unseen data sets in which one data set using the same model of OCTA device as of the primary data set and two data sets using another brand of OCTA device. We assessed the performance by using the area under the receiver operating characteristic curves with sensitivities, specificities, and accuracies and the area under the precision-recall curves with precision. RESULTS For the image quality assessment, analyses for gradability and measurability assessment were performed. Our deep-learning system achieved the area under the receiver operating characteristic curves >0.948 and area under the precision-recall curves >0.866 for the gradability assessment, area under the receiver operating characteristic curves >0.960 and area under the precision-recall curves >0.822 for the measurability assessment, and area under the receiver operating characteristic curves >0.939 and area under the precision-recall curves >0.899 for the DMI assessment across three external validation data sets. Grad-CAM demonstrated the capability of our deep-learning system paying attention to regions related to DMI identification. CONCLUSION Our proposed multitask deep-learning system might facilitate the development of a simplified assessment of DMI on OCTA images among individuals with diabetes mellitus at high risk for visual loss.
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4.
Retinopathy and Systemic Disease Morbidity in Severe COVID-19.
Shantha, JG, Auld, SC, Anthony, C, Ward, L, Adelman, MW, Maier, CL, Price, KW, Jacob, JT, Fashina, T, Randleman, C, et al
Ocular immunology and inflammation. 2021;(4):743-750
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Abstract
PURPOSE To assess the prevalence of retinopathy and its association with systemic morbidity and laboratory indices of coagulation and inflammatory dysfunction in severe COVID-19. DESIGN Retrospective, observational cohort study. METHODS Adult patients hospitalized with severe COVID-19 who underwent ophthalmic examination from April to July 2020 were reviewed. Retinopathy was defined as one of the following: 1) Retinal hemorrhage; 2) Cotton wool spots; 3) Retinal vascular occlusion. We analyzed medical comorbidities, sequential organ failure assessment (SOFA) scores, clinical outcomes, and laboratory values for their association with retinopathy. RESULTS Thirty-seven patients with severe COVID-19 were reviewed, the majority of whom were female (n = 23, 62%), Black (n = 26, 69%), and admitted to the intensive care unit (n = 35, 95%). Fourteen patients had retinopathy (38%) with retinal hemorrhage in 7 (19%), cotton wool spots in 8 (22%), and a branch retinal artery occlusion in 1 (3%) patient. Patients with retinopathy had higher SOFA scores than those without retinopathy (8.0 vs. 5.3, p = .03), higher rates of respiratory failure requiring invasive mechanical ventilation and shock requiring vasopressors (p < .01). Peak D-dimer levels were 28,971 ng/mL in patients with retinopathy compared to 12,575 ng/mL in those without retinopathy (p = .03). Peak CRP was higher in patients with cotton wool spots versus those without cotton wool spots (354 mg/dL vs. 268 mg/dL, p = .03). Multivariate logistic regression modeling showed an increased risk of retinopathy with higher peak D-dimers (aOR 1.32, 95% CI 1.01-1.73, p = .04) and male sex (aOR 9.6, 95% CI 1.2-75.5, p = .04). CONCLUSION Retinopathy in severe COVID-19 was associated with greater systemic disease morbidity involving multiple organs. Given its association with coagulopathy and inflammation, retinopathy may offer insight into disease pathogenesis in patients with severe COVID-19.
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Findings from a Genotyping Study of Over 1000 People with Inherited Retinal Disorders in Ireland.
Whelan, L, Dockery, A, Wynne, N, Zhu, J, Stephenson, K, Silvestri, G, Turner, J, O'Byrne, JJ, Carrigan, M, Humphries, P, et al
Genes. 2020;(1)
Abstract
The Irish national registry for inherited retinal degenerations (Target 5000) is a clinical and scientific program to identify individuals in Ireland with inherited retinal disorders and to attempt to ascertain the genetic cause underlying the disease pathology. Potential participants first undergo a clinical assessment, which includes clinical history and analysis with multimodal retinal imaging, electrophysiology, and visual field testing. If suitable for recruitment, a sample is taken and used for genetic analysis. Genetic analysis is conducted by use of a retinal gene panel target capture sequencing approach. With over 1000 participants from 710 pedigrees now screened, there is a positive candidate variant detection rate of approximately 70% (495/710). Where an autosomal recessive inheritance pattern is observed, an additional 9% (64/710) of probands have tested positive for a single candidate variant. Many novel variants have also been detected as part of this endeavor. The target capture approach is an economic and effective means of screening patients with inherited retinal disorders. Despite the advances in sequencing technology and the ever-decreasing associated processing costs, target capture remains an attractive option as the data produced is easily processed, analyzed, and stored compared to more comprehensive methods. However, with decreasing costs of whole genome and whole exome sequencing, the focus will likely move towards these methods for more comprehensive data generation.
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An In-Vitro Cell Model of Intracellular Protein Aggregation Provides Insights into RPE Stress Associated with Retinopathy.
Keeling, E, Culling, AJ, Johnston, DA, Chatelet, DS, Page, A, Tumbarello, DA, Lotery, AJ, Ratnayaka, JA
International journal of molecular sciences. 2020;(18)
Abstract
Impaired cargo trafficking and the aggregation of intracellular macromolecules are key features of neurodegeneration, and a hallmark of aged as well as diseased retinal pigment epithelial (RPE) cells in the eye. Here, photoreceptor outer segments (POS), which are internalized daily by RPE cells, were modified by UV-irradiation to create oxidatively modified POS (OxPOS). Oxidative modification was quantified by a protein carbonyl content assay. Human ARPE-19 cells were synchronously pulsed with POS or OxPOS to study whether oxidatively modified cargos can recapitulate features of RPE pathology associated with blinding diseases. Confocal immunofluorescence microscopy analysis showed that OxPOS was trafficked to LAMP1, LAMP2 lysosomes and to LC3b autophagy vacuoles. Whilst POS were eventually degraded, OxPOS cargos were sequestered in late compartments. Co-localization of OxPOS was also associated with swollen autolysosomes. Ultrastructural analysis revealed the presence of electron-dense OxPOS aggregates in RPE cells, which appeared to be largely resistant to degradation. Measurement of cellular autofluorescence, using parameters used to assess fundus autofluorescence (FAF) in age-related macular disease (AMD) patients, revealed that OxPOS contributed significantly to a key feature of aged and diseased RPE. This in vitro cell model therefore represents a versatile tool to study disease pathways linked with RPE damage and sight-loss.
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Noncompliance in Prospective Retina Clinical Trials: Analysis of Factors Predicting Loss to Follow-up.
Zhou, B, Mitchell, TC, Rusakevich, AM, Brown, DM, Wykoff, CC
American journal of ophthalmology. 2020;:86-96
Abstract
PURPOSE Noncompliance during prospective studies can bias results and limit conclusions. The current study retrospectively investigated the relationship between study subject characteristics and rates of noncompliance in interventional trials involving common causes of blindness. DESIGN Retrospective analysis of 10 randomized clinical trials. METHODS Subjects were enrolled in investigator-initiated trials studying proliferative diabetic retinopathy, neovascular age-related macular degeneration, diabetic macular edema, and retinal venous occlusive disease. Records were reviewed for hypothesized risk factors of noncompliance and rates of noncompliance, which were defined as at least 1 missed visit or exiting the study early. Demographic information, systemic medical history, and ocular medical history, including visual acuity and central retinal thicknesses, were examined retrospectively using Student t test, Pearson χ2 test, and logistic regression. RESULTS Of 390 subjects included, 212 (54.4%) were compliant with all scheduled study visits and 178 (45.6%) met criteria for noncompliance, with 53 (13.6%) subjects exiting early. Regression models identified 17 variables that were significant in determining subject noncompliance. Among those, distance, comorbidities, diabetic status, concomitant medications, previous clinic visits, length of study, disease under study, and severe adverse events were highly significant risk factors of noncompliance. CONCLUSION The current research identified a substantial proportion of subjects who met the criteria for noncompliance within the trials analyzed. The factors identified in the current work are consistent with published clinical observations and the results of previous clinical trials. These results highlight the importance of considering study design and medical history when designing prospective clinical trials in an attempt to minimize data loss.
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New Insights Into Immunological Therapy for Retinal Disorders.
Takeda, A, Yanai, R, Murakami, Y, Arima, M, Sonoda, KH
Frontiers in immunology. 2020;:1431
Abstract
In the twentieth century, a conspicuous lack of effective treatment strategies existed for managing several retinal disorders, including age-related macular degeneration; diabetic retinopathy (DR); retinopathy of prematurity (ROP); retinitis pigmentosa (RP); uveitis, including Behçet's disease; and vitreoretinal lymphoma (VRL). However, in the first decade of this century, advances in biomedicine have provided new treatment strategies in the field of ophthalmology, particularly biologics that target vascular endothelial growth factor or tumor necrosis factor (TNF)-α. Furthermore, clinical trials on gene therapy specifically for patients with autosomal recessive or X-linked RP have commenced. The overall survival rates of patients with VRL have improved, owing to earlier diagnoses and better treatment strategies. However, some unresolved problems remain such as primary or secondary non-response to biologics or chemotherapy, and the lack of adequate strategies for treating most RP patients. In this review, we provide an overview of the immunological mechanisms of the eye under normal conditions and in several retinal disorders, including uveitis, DR, ROP, RP, and VRL. In addition, we discuss recent studies that describe the inflammatory responses that occur during the course of these retinal disorders to provide new insights into their diagnosis and treatment.
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Mitochondrial Dysfunction as a Novel Target for Neuroprotective Nutraceuticals in Ocular Diseases.
Huang, CP, Lin, YW, Huang, YC, Tsai, FJ
Nutrients. 2020;(7)
Abstract
The eyes require a rich oxygen and nutrient supply; hence, the high-energy demand of the visual system makes it sensitive to oxidative stress. Excessive free radicals result in mitochondrial dysfunction and lead to retinal neurodegeneration, as an early stage of retinal metabolic disorders. Retinal cells are vulnerable because of their coordinated interaction and intricate neural networks. Nutraceuticals are believed to target multiple pathways and have shown neuroprotective benefits by scavenging free radicals and promoting mitochondrial gene expression. Furthermore, encouraging results demonstrate that nutraceuticals improve the organization of retinal cells and visual functions. This review discusses the mitochondrial impairments of retinal cells and the mechanisms underlying the neuroprotective effects of nutraceuticals. However, some unsolved problems still exist between laboratory study and clinical therapy. Poor bioavailability and bioaccessibility strongly limit their development. A new delivery system and improved formulation may offer promise for health care applications.
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Impact of LDL Cholesterol on Microvascular Versus Macrovascular Disease: A Mendelian Randomization Study.
Emanuelsson, F, Nordestgaard, BG, Tybjærg-Hansen, A, Benn, M
Journal of the American College of Cardiology. 2019;(11):1465-1476
Abstract
BACKGROUND Low-density lipoprotein cholesterol (LDL-C) is causally associated with a high risk of coronary artery disease. Whether this also holds for a spectrum of peripheral vascular diseases is unknown. OBJECTIVES The purpose of this study was to determine whether high LDL-C causally relates to risk of retinopathy, neuropathy, chronic kidney disease (CKD), and peripheral arterial disease (PAD) in the general population. METHODS One-sample Mendelian randomization (MR) of 116,419 Danish individuals, 2-sample MR on summary-level data from the Global Lipid Genetics Consortium (GLGC) (n = 94,595) and the UK Biobank (n = 408,455), and meta-analysis of randomized statin trials (n = 64,134) were performed. RESULTS Observationally, high LDL-C did not associate with high risk of retinopathy or neuropathy. There were stepwise increases in risk of CKD and PAD with higher LDL-C (both p for trend <0.001), with hazard ratios of 1.05 (95% confidence interval [CI]: 0.97 to 1.13) for CKD, and 1.41 (95% CI: 1.23 to 1.62) for PAD in individuals with LDL-C above the 95th percentile versus below the 50th percentile. In genetic, causal analyses in the Copenhagen studies, the risk ratio of disease for a 1 mmol/l higher LDL-C was 1.06 (95% CI: 0.24 to 4.58) for retinopathy, 1.05 (95% CI: 0.64 to 1.72) for neuropathy, 3.83 (95% CI: 2.00 to 7.34) for CKD, and 2.09 (95% CI: 1.30 to 2.38) for PAD. Summary-level data from the GLGC and the UK Biobank for retinopathy, neuropathy, and PAD gave similar results. For CKD, a 1-mmol/l lower LDL-C conferred a higher eGFR of 1.95 ml/min/1.73 m2 (95% CI: 1.88 to 2.02 ml/min/1.73 m2) observationally, 5.92 ml/min/1.73 m2 (95% CI: 4.97 to 6.86 ml/min/1.73 m2) genetically, and 2.69 ml/min/1.73 m2 (95% CI: 1.48 to 3.94 ml/min/1.73 m2) through statin therapy. CONCLUSIONS High LDL-C was not causally associated with risk of retinopathy and neuropathy; however, high LDL-C was observationally and genetically associated with high risks of PAD and CKD, suggesting that LDL-C is causally involved in the pathogenesis of these diseases.