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Optical Coherence Tomography Angiography: Review of Current Technical Aspects and Applications in Chorioretinal Disease.
Wang, JC, Miller, JB
Seminars in ophthalmology. 2019;(4):211-217
Abstract
Optical coherence tomography angiography (OCT-A) has enabled fast, non-invasive, high-resolution visualization of vasculature within the eye. In the past few years, it has become increasingly utilized for a range of disorders including age-related macular degeneration, diabetic retinopathy, retinal vein occlusions, and uveitis among others. This article reviews technical aspects of OCT-A, its applications in chorioretinal disease, and known limitations of the technology.
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Implication of Deep-Vascular-Layer Alteration Detected by Optical Coherence Tomography Angiography for the Pathogenesis of Diabetic Retinopathy.
Dimitrova, G, Chihara, E
Ophthalmologica. Journal international d'ophtalmologie. International journal of ophthalmology. Zeitschrift fur Augenheilkunde. 2019;(4):179-182
Abstract
The aim of this narrative mini review is to analyze optical coherence tomography angiography (OCTA) parameters from reports that involved both superficial and deep vascular layers in patients with diabetes and to assess their relevance for the pathogenesis of diabetic retinopathy (DR). Papers published from January 2015 to August 2018 describing the use of OCTA in diabetes were identified and reviewed through a Medline/PubMed search. OCTA studies suggest that parameters are altered in patients with diabetes in all retinal vascular layers. From all included studies that evaluated both the superficial and the deep vascular layer, a number of studies suggested that the deep vascular layer was affected at an earlier stage of DR. OCTA parameter alterations were more prominent in the deep vascular layer than in the superficial vascular layer in patients with DR, and deep-vascular-layer alterations were most evident in patients with diabetic macular edema. Regarding that retinal venules originate from the deep vascular layer of the retina, alteration of OCTA parameters at the deep vascular layer in diabetic patients may imply a predominant affection of the venous side of the retinal vascular system in the pathogenesis of DR.
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Sickle cell retinopathy. A focused review.
Abdalla Elsayed, MEA, Mura, M, Al Dhibi, H, Schellini, S, Malik, R, Kozak, I, Schatz, P
Graefe's archive for clinical and experimental ophthalmology = Albrecht von Graefes Archiv fur klinische und experimentelle Ophthalmologie. 2019;(7):1353-1364
Abstract
PURPOSE To provide a focused review of sickle cell retinopathy in the light of recent advances in the pathogenesis, multimodal retinal imaging, management of the condition, and migration trends, which may lead to increased prevalence of the condition in the Western world. METHODS Non-systematic focused literature review. RESULTS Sickle retinopathy results from aggregation of abnormal hemoglobin in the red blood cells in the retinal microcirculation, leading to reduced deformability of the red blood cells, stagnant blood flow in the retinal precapillary arterioles, thrombosis, and ischemia. This may be precipitated by hypoxia, acidosis, and hyperosmolarity. Sickle retinopathy may result in sight threatening complications, such as paracentral middle maculopathy or sequelae of proliferative retinopathy, such as vitreous hemorrhage and retinal detachment. New imaging modalities, such as wide-field imaging and optical coherence tomography angiography, have revealed the microstructural features of sickle retinopathy, enabling earlier diagnosis. The vascular growth factor ANGPTL-4 has recently been identified as a potential mediator of progression to proliferative retinopathy and may represent a possible therapeutic target. Laser therapy should be considered for proliferative retinopathy in order to prevent visual loss; however, the evidence is not very strong. With recent development of wide-field imaging, targeted laser to ischemic retina may prove to be beneficial. Exact control of intraoperative intraocular pressure, including valved trocar vitrectomy systems, may improve the outcomes of vitreoretinal surgery for complications, such as vitreous hemorrhage and retinal detachment. Stem cell transplantation and gene therapy are potentially curative treatments, which may prevent retinopathy. CONCLUSIONS There is lack of evidence regarding the optimal management of sickle retinopathy. Further study is needed to determine if recent progress in the understanding of the pathophysiology and diagnosis of sickle retinopathy may translate into improved management and outcome.
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Application of optical coherence tomography angiography in diabetic retinopathy: a comprehensive review.
Akil, H, Karst, S, Heisler, M, Etminan, M, Navajas, E, Maberley, D
Canadian journal of ophthalmology. Journal canadien d'ophtalmologie. 2019;(5):519-528
Abstract
Optical coherence tomography angiography (OCTA) is a noninvasive method that enables visualization of blood flow within retinal vessels down to the size of capillaries by detecting motion contrast from moving blood cells. OCTA provides a fast and safe procedure to assess retinal microvasculature with higher contrast and resolution than conventional fluorescence angiography. The different capillary plexuses are displayed separately and their perfusion density can be quantified. Imaging capabilities such as these have led to an emerging field of clinical application for OCTA in vascular diseases such as diabetic retinopathy (DR). Evaluation of parameters such as parafoveal capillary perfusion density could be a biomarker for disease diagnosis and progression. Typical microvascular changes in DR such as capillary nonperfusion, microaneurysms, intraretinal microvascular abnormalities, and neovascularization can be reliably detected in optical coherence tomography angiograms, characterized in detail and attributed to the different capillary plexuses. Monitoring of these lesions in vivo gives potential novel insight into the pathophysiology in DR. The aim of this article is to summarize the potential applications/utility of OCTA in DR reported in the literature.
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New insights into diabetic retinopathy by OCT angiography.
Liu, G, Xu, D, Wang, F
Diabetes research and clinical practice. 2018;:243-253
Abstract
Diabetic retinopathy (DR) is one of the most common diabetic complications, which has become a leading cause for vision loss, mainly because of macular edema and vitreous hemorrhage. Optical coherence tomography (OCT) angiography is a novel technique to visualize vascular changes including microaneurysm, non-perfusion area, intraretinal microvascular abnormalities, and neovascularization. Recently, it is possible to quantify vascular density, foveal avascular zone area, non-perfusion area objectively using OCT angiography. In addition, OCT angiography also provides an alternative method to evaluate the effect of anti-vascular endothelial growth factor (VEGF) treatments by providing high resolution images of macular microcirculatory abnormalities. Thus OCT angiography is an effective method to investigate the vascular changes of the disease, and can also be potentially applied in the diagnosis, treatment, and follow up of DR.
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Multimodal imaging of diabetic retinopathy.
Tran, K, Pakzad-Vaezi, K
Current opinion in ophthalmology. 2018;(6):566-575
Abstract
PURPOSE OF REVIEW Diabetic retinopathy is the most common microvascular complication of diabetes mellitus and a leading cause of blindness throughout the world. Ocular imaging continues to play a vital role in the diagnosis, management and monitoring of diabetic retinopathy. Major technological advancements in imaging over the past decade have improved our understanding and knowledge of diabetic retinopathy and therefore a multimodal approach to imaging has become the standard of care. RECENT FINDINGS Updates to traditional technologies such as digital fundus photography along with recent advancements in optical coherence tomography (OCT) and OCT angiography (OCTA) have provided clinicians with new information and improved efficiency. SUMMARY In this review, we describe the benefits and clinical applications of several imaging techniques in diabetic retinopathy including color photography, fluorescein angiography, OCT, OCTA and adaptive optics. Understanding the indications and limitations of each technology allows clinicians to gain the most information from each modality and thereby optimize patient care.
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Near-Infrared Fluorescence Imaging for Real-Time Intraoperative Guidance in Anastomotic Colorectal Surgery: A Systematic Review of Literature.
van den Bos, J, Al-Taher, M, Schols, RM, van Kuijk, S, Bouvy, ND, Stassen, LPS
Journal of laparoendoscopic & advanced surgical techniques. Part A. 2018;(2):157-167
Abstract
PURPOSE The aims of this review are to determine the feasibility of near-infrared fluorescence (NIRF) angiography in anastomotic colorectal surgery and to determine the effectiveness of the technique in improving imaging and quantification of vascularization, thereby aiding in decision making as to where to establish the anastomosis. METHODS A systematic literature search of PubMed and EMBASE was conducted. Searching through the reference lists of selected articles identified additional studies. All English language articles presenting original patient data regarding intraoperative NIRF angiography were included without restriction of type of study, except for case reports, technical notes, and video vignettes. The intervention consisted of intraoperative NIRF angiography during anastomotic colorectal surgery to assess perfusion of the colon, sigmoid, and/or rectum. Primary outcome parameters included ease of use, added surgical time, complications related to the technique, and costs. Other relevant outcomes were whether this technique changed intraoperative decision making, whether effort was taken by the authors to quantify the signal and the incidence of postoperative complications. RESULTS Ten studies were included. Eight of these studies make a statement about the ease of use. In none of the studies complications due to the use of the technique occurred. The technique changed the resection margin in 10.8% of all NIRF cases. The anastomotic leak rate was 3.5% in the NIRF group and 7.4% in the group with conventional imaging. Two of the included studies used an objective quantification of the fluorescence signal and perfusion, using ROIs (Hamamatsu Photonics) and IC-CalcĀ® respectively. CONCLUSIONS Although the feasibility of the technique seems to be agreed on by all current research, large clinical trials are mandatory to further evaluate the added value of the technique.
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8.
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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Abstract
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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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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Abstract
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.