الفهرس 
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Abstract
Hypertension is the fourth leading cause of mortality globally and a key risk factor for cardiovascular disease. Hypertension is a risk factor for systemic diseases and can lead to target organ damage. Specifically, high blood pressure can cause a variety of adverse reactions in the eyes, inevitably leading to retinopathy, optic neuropathy, and choroidal disease. Hypertensive retinopathy (HR) is a condition in which the retinal vessels are damaged as a result of high blood pressure. There is substantial evidence that hypertensive retinopathy is a predictor of target-organ damage TOD-related systemic morbidity and death. Optical coherence tomography (OCT) is a non-invasive highresolution optical imaging method that uses interference between a signal from an item under examination and a nearby reference signal to produce images. OCT can generate a cross-section picture of an object in real time, i.e., a two-dimensional image in space (lateral coordinate, axial coordinate). Optical coherence tomography angiography (OCTA) is a noninvasive imaging technique that uses motion contrast imaging to produce angiographic pictures in seconds utilizing high-resolution volumetric blood flow data. A map of blood flow is constructed by comparing the decorrelation signal (differences in the backscattered OCT signal intensity or amplitude) across successive OCT b-scans obtained at the same crosssection. Our research was implemented in order to study to investigate sensitivity of Optical coherence tomography (OCT) and Optical coherence tomography angiography (OCT-A) metrics in grading hypertensive retinopathy in comparison with the gold standard colour fundus photographs for HTR grading. This study included 120 eyes. Hypertensive and control groups were recruited from the Ophthalmology department in Tanta university hospital and asked to participate in this study. This study was designed as a prospective cross-sectional controlled study in the period from 11/2020 to 11/2021. Study Subjects: Eyes were divided into 2 groups: 1- Hypertension patients‟ group: include 45 patients with hypertensive retinopathy diagnosed clinically and by fundus examination and including the 3 HTN grades (15 patients in each group) 2- Control group: include 15 age-matched subjects. symptoms and signs of hypertension were ruled out clinically and by fundus examination in the control group. We defined hypertension according to World Health Organization WHO-ISH guidelines as chronically elevated blood pressure as systolic greater than 140 mmHg and diastolic greater than 90 mmHg. The controls (group N) had normal blood pressure. Hypertensive Retinopathy was graded into grade I, grade II, grade III as Keith -Wagner- Barker classification. Image acquisition with colour fundus Photographs for the central part of the fundus, SS-OCT and OCT angiography. All study participants did a swept-source (SS)-OCT examination (DRI Triton, Topcon, Tokyo, Japan), which employs a swept light source with a wavelength of 1,050-nm and a scanning speed of 100,000 A-scans/second. Optical coherence topography OCT was used to obtain: - a- A six-line radial pattern scan focused on the fovea from each eye was used to determine retinal thickness at the fovea. b- Choroidal thickness assessed at 2 mm from the fovea (nasal, temporal, superior, and inferior). from each eye, we received a six-line radial pattern scan (1,024 Ascans) focused on the fovea. The vertical distance between the posterior margin of the hyper-reflective retinal pigment epithelium and the choroid/sclera junction was used to define choroidal thickness. Optical coherence topography angiography OCTA was used to obtain: - To study (qualitatively and quantitatively) a) Quantitative measurement of the Foveal Avascular Zone (FAZ) at SCP using the (6x6 mm scan) On OCT angiography pictures at the SCP, we manually defined the FAZ region and boundary along the innermost capillaries. b) Superficial capillary plexus (SCP) and Deep capillary plexus (DCP) at the parafoveal region (6x6 mm scan) export as images Angio 1 & Angio 2. c) Measuring the density map of choroidal vessels in the (6x6 mm scan) (export as images Angio 4). d) Peripapillary area vessel density in the (4.5 x 4.5 mm scan) export as images Angio 3. All images were collected and the areas were calculated using Image J software The findings revealed that: The central foveal thickness showed a decrease in participants with hypertensive retinopathy grade I compared to normal controls, while an increase in thickness in participants with hypertensive retinopathy grade II & III. The sub foveal choroidal thickness show decrease in participants with hypertensive retinopathy grade I & grade II compared to normal controls, whereas there is a significant increase in the sub foveal choroidal thickness in participants with hypertensive retinopathy grade III. The foveal avascular zone is a significant increase in the participants with hypertensive retinopathy grades I, II, III compared to normal controls. There is decrease in vessel density, skeletonized vessel density of superficial capillary plexus, and deep capillary plexus in the different stages of hypertensive retinopathy. The peripapillary capillary density showed a decrease in participants with hypertensive retinopathy grade I, II compared to normal controls.