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Impact of Arterial Hypertension on the Eye: A Review of the Pathogenesis, Diagnostic Methods, and Treatment of Hypertensive Retinopathy.
Dziedziak, J, Zaleska-Żmijewska, A, Szaflik, JP, Cudnoch-Jędrzejewska, A
Medical science monitor : international medical journal of experimental and clinical research. 2022;:e935135
Abstract
The number of patients with arterial hypertension is continually increasing. Hypertension can cause organ complications, called hypertension-mediated organ damage (HMOD). One example is hypertensive retinopathy, in which high blood pressure (BP) damages both the retinal microcirculation and the retinal nerve fiber layer (RNFL). This can result in progressive and painless vision deterioration in some groups of patients. Unlike anywhere else in the human body, the microvasculature of the retina can be observed in vivo, and the progression of changes can be closely monitored. The harmful effect of increased BP on the eye is not only limited to hypertensive retinopathy, but can also lead to an exacerbation of diabetic retinopathy (DR) and to an increase in intraocular pressure (IOP), and it can also trigger the formation of thromboembolic lesions. This review presents an update on the pathogenesis of hypertensive retinopathy and the use of adaptive optics (AO) combined with optical coherence tomography (OCT) to evaluate the retinal microvasculature. The latest progress and directions of research in the field of hypertensive retinopathy are also discussed.
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OCT imaging of rod mitochondrial respiration in vivo.
Berkowitz, BA, Qian, H
Experimental biology and medicine (Maywood, N.J.). 2021;(20):2151-2158
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There remains a need for high spatial resolution imaging indices of mitochondrial respiration in the outer retina that probe normal physiology and measure pathogenic and reversible conditions underlying loss of vision. Mitochondria are involved in a critical, but somewhat underappreciated, support system that maintains the health of the outer retina involving stimulus-evoked changes in subretinal space hydration. The subretinal space hydration light-dark response is important because it controls the distribution of vision-critical interphotoreceptor matrix components, including anti-oxidants, pro-survival factors, ions, and metabolites. The underlying signaling pathway controlling subretinal space water management has been worked out over the past 30 years and involves cGMP/mitochondria respiration/pH/RPE water efflux. This signaling pathway has also been shown to be modified by disease-generating conditions, such as hypoxia or oxidative stress. Here, we review recent advances in MRI and commercially available OCT technologies that can measure stimulus-evoked changes in subretinal space water content based on changes in the external limiting membrane-retinal pigment epithelium region. Each step within the above signaling pathway can also be interrogated with FDA-approved pharmaceuticals. A highlight of these studies is the demonstration of first-in-kind in vivo imaging of mitochondria respiration of any cell in the body. Future examinations of subretinal space hydration are expected to be useful for diagnosing threats to sight in aging and disease, and improving the success rate when translating treatments from bench-to-bedside.
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Correlation of OCT Angiography Vessel Densities and the Early Treatment Diabetic Retinopathy Study Grading Scale.
Mehta, NS, Lee, JG, Gupta, L, Zhou, DB, Andrade Romo, JS, Castanos, MV, Jansen, M, Ping Chui, TY, Rosen, RB
Ophthalmology. Retina. 2021;(7):714-715
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Role of Inflammation in Classification of Diabetic Macular Edema by Optical Coherence Tomography.
Chung, YR, Kim, YH, Ha, SJ, Byeon, HE, Cho, CH, Kim, JH, Lee, K
Journal of diabetes research. 2019;:8164250
Abstract
Diabetic macular edema (DME) is the abnormal accumulation of fluid in the subretinal or intraretinal spaces in the macula in patients with diabetic retinopathy and leads to severely impaired central vision. Technical developments in retinal imaging systems have led to many advances in the study of DME. In particular, optical coherence tomography (OCT) can provide longitudinal and microstructural analysis of the macula. A comprehensive review was provided regarding the role of inflammation using OCT-based classification of DME and current and ongoing therapeutic approaches. In this review, we first describe the pathogenesis of DME, then discuss the classification of DME based on OCT findings and the association of different types of DME with inflammation, and finally describe current and ongoing therapeutic approaches using OCT-based classification of DME. Inflammation has an important role in the pathogenesis of DME, but its role appears to differ among the DME phenotypes, as determined by OCT. It is important to determine how the different DME subtypes respond to intravitreal injections of steroids, antivascular endothelial growth factor agents, and other drugs to improve prognosis and responsiveness to treatment.
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Optical coherence tomography angiography (OCTA) flow speed mapping technology for retinal diseases.
Arya, M, Rashad, R, Sorour, O, Moult, EM, Fujimoto, JG, Waheed, NK
Expert review of medical devices. 2018;(12):875-882
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INTRODUCTION Optical coherence tomography angiography (OCTA) is a noninvasive imaging modality for depth-resolved visualization of retinal vasculature. Angiographic data couples with structural data to generate a cube scan, from which en-face images of vasculature can be obtained at various axial positions. OCTA has expanded understanding of retinal vascular disorders and has primarily been used for qualitative analysis. AREAS COVERED Recent studies have explored the quantitative properties of OCTA, which would allow for objective assessment and follow-up of retinal pathologies. Various quantitative metrics have been developed, such as foveal avascular zone area and vessel density. However, quantitative assessment of the characteristics of retinal blood flow remains limited, as OCTA provides an image depicting either the presence or absence of flow at a particular region without information of relative velocities. The development of variable interscan time analysis (VISTA) overcomes this limitation. The VISTA algorithm generates a color-coded map of relative blood flow speeds. VISTA has already demonstrated utility in furthering our understanding of various retinal pathologies, such as geographic atrophy, choroidal neovascularization, aneurysmal type 1 neovascularization, and diabetic retinopathy. EXPERT COMMENTARY VISTA, an OCTA flow speed mapping technique, may have a role in developing the utility of OCTA as a screening tool.
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Use of OCTA, FA, and Ultra-Widefield Imaging in Quantifying Retinal Ischemia: A Review.
Or, C, Sabrosa, AS, Sorour, O, Arya, M, Waheed, N
Asia-Pacific journal of ophthalmology (Philadelphia, Pa.). 2018;(1):46-51
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As ischemia remains a key prognostic factor in the management of various diseases including diabetic retinopathy, an increasing amount of research has been dedicated to its quantification as a potential biomarker. Advancements in the quantification of retinal ischemia have been made with the imaging modalities of fluorescein angiography (FA), ultra-widefield imaging (UWF), and optical coherence tomography angiography (OCTA), with each imaging modality offering certain benefits over the others. FA remains the gold standard in assessing the extent of ischemia. UWF imaging has allowed for the assessment of peripheral ischemia via FA. It is, however, OCTA that offers the best visualization of retinal vasculature with its noninvasive depth-resolved imaging and therefore has the potential to become a mainstay in the assessment of retinal ischemia. The primary purpose of this article is to review the use of FA, UWF, and OCTA to quantify retinal ischemia and the various methods described in the literature by which this is achieved.
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Optical coherence tomography angiography.
Spaide, RF, Fujimoto, JG, Waheed, NK, Sadda, SR, Staurenghi, G
Progress in retinal and eye research. 2018;:1-55
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Optical coherence tomography (OCT) was one of the biggest advances in ophthalmic imaging. Building on that platform, OCT angiography (OCTA) provides depth resolved images of blood flow in the retina and choroid with levels of detail far exceeding that obtained with older forms of imaging. This new modality is challenging because of the need for new equipment and processing techniques, current limitations of imaging capability, and rapid advancements in both imaging and in our understanding of the imaging and applicable pathophysiology of the retina and choroid. These factors lead to a steep learning curve, even for those with a working understanding dye-based ocular angiography. All for a method of imaging that is a little more than 10 years old. This review begins with a historical account of the development of OCTA, and the methods used in OCTA, including signal processing, image generation, and display techniques. This forms the basis to understand what OCTA images show as well as how image artifacts arise. The anatomy and imaging of specific vascular layers of the eye are reviewed. The integration of OCTA in multimodal imaging in the evaluation of retinal vascular occlusive diseases, diabetic retinopathy, uveitis, inherited diseases, age-related macular degeneration, and disorders of the optic nerve is presented. OCTA is an exciting, disruptive technology. Its use is rapidly expanding in clinical practice as well as for research into the pathophysiology of diseases of the posterior pole.
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Optical Coherence Tomography Angiography in Healthy Subjects and Diabetic Patients.
Coscas, G, Lupidi, M, Coscas, F, Chhablani, J, Cagini, C
Ophthalmologica. Journal international d'ophtalmologie. International journal of ophthalmology. Zeitschrift fur Augenheilkunde. 2018;(2-3):61-73
Abstract
Fluorescein angiography and indocyanine green angiography provide information about the normal retinal and choroidal vascular perfusion. They allow the evaluation of different diseases and increase the capability to define and diagnose several pathological conditions. Fluorescein angio graphy is the "gold standard" in imaging the retinal vascular bed and its changes, although not all the different layers of the capillary network can be visualized in a bidimensional examination. Optical coherence tomography angiography allows a depth-resolved visualization of the retinal and choroidal microvasculature, by calculating the difference (decorrelation) between static and nonstatic tissue. Given that the main moving elements in the eye fundus are contained in vessels, determining a vascular decorrelation signal permits a three-dimensional visualization of the retinal and choroidal vascular network without the administration of an intravenous dye. Moreover, a complete morphofunctional assessment may help in defining both the origin and the clinical activity of different vascular diseases such as diabetic retinopathy.
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Viewing the choroid: where we stand, challenges and contradictions in diabetic retinopathy and diabetic macular oedema.
Campos, A, Campos, EJ, Martins, J, Ambrósio, AF, Silva, R
Acta ophthalmologica. 2017;(5):446-459
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Diabetic macular oedema (DMO) is the leading cause of vision loss in the working-age population. Blood-retinal barrier (BRB) dysfunction in diabetic retinopathy (DR), mainly at the level of the retinal vessels, has long been related with leakage and fluid accumulation, leading to macular oedema. However, the nourishment of the macula is provided by the choroid and a diabetic choroidopathy has been described. Therefore, there has been a growing interest in studying the role of the choroid in the pathophysiology of DR and DMO, mainly by optical coherence tomography (OCT). Nevertheless, there are conflicting results in the different studies. We summarize the results from the available studies, describe the limitations and confounding factors and discuss future procedures to avoid bias.
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The neurovascular unit and the pathophysiologic basis of diabetic retinopathy.
Gardner, TW, Davila, JR
Graefe's archive for clinical and experimental ophthalmology = Albrecht von Graefes Archiv fur klinische und experimentelle Ophthalmologie. 2017;(1):1-6
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PURPOSE To relate the concept of the retinal neurovascular unit and its alterations in diabetes to the pathophysiology of diabetic retinopathy. METHODS Case illustrations and conceptual frameworks are presented that illustrate adaptive and maladaptive "dis-integration" of the retinal neurovascular unit with the progression of diabetes. RESULTS Retinopathy treatment should address pathophysiologic processes rather than pathologic lesions as is current practice. CONCLUSIONS Future improvements in the treatment of diabetic retinopathy requires deeper understanding of the cellular and molecular changes induced by diabetes, coupled with the use of quantitative phenotyping methods that assess the pathophysiologic processes.