An algorithm called optical angiography (OAG) technique, and later an algorithm known as ultrahigh sensitive optical microangiography (OMAG) have been developed to distinguish blood flow from background ( 11, 12) By analyzing the spatial and temporal statistics of speckle patterns, Enfield et al. Angiography of complex OCT signal is captured by the related changes between signal frequency and phase, mainly by the Doppler Effect and backscattering. The intrinsic principles of OCT angiography are based on complex OCT signal, amplitude of OCT signal, or phase of OCT signal ( 9, 10). OCTA not only inherits the non-invasive depth-resolved features in living tissues with high resolution of traditional OCT, but also can identify retinal vascular abnormalities which traditional OCT is unable to do ( 8). Considering the commonly use of OCT system in ophthalmology, researchers have improved contrast to identify the signal of blood flow from periphery tissues and explored the traditional OCT to the OCT angiography (OCTA) successfully. However, these techniques are restricted for widely clinical use because of the poor reproducibility, difficulty of application and large variation in parameters of blood flow among human beings. In order to visualize vascular structures, many techniques have been devised to measure blood flow, such as ultrasound technique, blue field entoptoscopy, and laser Doppler velocimetry ( 6, 7). However, it cannot display and identify retinal vascular abnormalities. Without ionizing radiation, OCT has been widely used to obtain detailed morphology of the retina ( 5). Optical coherence tomography (OCT) provides instant, depth-resolved and direct imaging of live eye tissue based on low-coherence interferometry. However, FA is invasive and requires intravenous dye injection, which can cause anaphylaxis side effects. Fluorescein angiography (FA) can visualize leakage, nonperfusion and vessel abnormalities to guide treatments. It is easy, cheap, non-invasive, but fails to show vessel leakage and nonperfusion area. As we all know, fundus photography (FP) is most commonly used to grade DR severity (ETDRS study). The grading of DR severity can be based on certain fundus images and the pathological changes of DR are now better visualized than before. Monitoring the severity scales of DR guides treatment and indicates prognosis. According to the severity and clinical progress, DR can be graded into two periods, nonproliferative diabetic retinopathy (NPDR) and proliferative diabetic retinopathy (PDR) characterized by the presence of neovascularization ( 4). Therefore, the early diagnosis, prompt prevention and treatment are very important for patients with DR. According to WHO 2002 census, 1.8 million blindness cases have been reported due to DR ( 2).ĭR is the most common cause of blindness in the working-age population ( 3). Diabetic retinopathy (DR) is one of the most common complications of type 1 or type 2 diabetes. There will be 30 million diabetic patients in USA and more than 40 million in China in 2030 ( 1). The estimated cases of diabetes will keep on rising and almost double in year 2030 compared to year 2000. Received: 16 March 2017 Accepted: 07 June 2017 Published: 11 July 2017.ĭiabetes is one of the most common diseases in the world and affects about 6% of the world’s population. Keywords: Diabetic retinopathy optical coherence tomography (OCT) angiography optical coherence tomography angiography (OCTA) Policy of Dealing with Allegations of Research Misconduct.Policy of Screening for Plagiarism Process.
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