Retinal Artery Occlusion: Sudden ISCHEMIA in the RETINA due to blocked blood flow through the CENTRAL RETINAL ARTERY or its branches leading to sudden complete or partial loss of vision, respectively, in the eye.Retinal Artery: Central retinal artery and its branches. It arises from the ophthalmic artery, pierces the optic nerve and runs through its center, enters the eye through the porus opticus and branches to supply the retina.Retinal Vein: Central retinal vein and its tributaries. It runs a short course within the optic nerve and then leaves and empties into the superior ophthalmic vein or cavernous sinus.Ophthalmic Artery: Artery originating from the internal carotid artery and distributing to the eye, orbit and adjacent facial structures.Ophthalmodynamometry: Measurement of the blood pressure of the retinal vessels. It is used also for the determination of the near point of convergence (CONVERGENCE, OCULAR). (From Cline, et al., Dictionary of Visual Science, 4th ed)Arteries: The vessels carrying blood away from the heart.Ciliary Arteries: Three groups of arteries found in the eye which supply the iris, pupil, sclera, conjunctiva, and the muscles of the iris.Susac Syndrome: A rare disorder consisting of microangiopathy of brain, retina, and inner ear ARTERIOLES. It is characterized by the clinical triad of encephalopathy, BRANCH RETINAL ARTERY OCCLUSION and VERTIGO/hearing loss.Fluorescein Angiography: Visualization of a vascular system after intravenous injection of a fluorescein solution. The images may be photographed or televised. It is used especially in studying the retinal and uveal vasculature.Retinal Vessels: The blood vessels which supply and drain the RETINA.Ultrasonography, Doppler, Color: Ultrasonography applying the Doppler effect, with the superposition of flow information as colors on a gray scale in a real-time image. This type of ultrasonography is well-suited to identifying the location of high-velocity flow (such as in a stenosis) or of mapping the extent of flow in a certain region.Retinal DiseasesFundus Oculi: The concave interior of the eye, consisting of the retina, the choroid, the sclera, the optic disk, and blood vessels, seen by means of the ophthalmoscope. (Cline et al., Dictionary of Visual Science, 4th ed)Pulmonary Artery: The short wide vessel arising from the conus arteriosus of the right ventricle and conveying unaerated blood to the lungs.Retinal Vein Occlusion: Blockage of the RETINAL VEIN. Those at high risk for this condition include patients with HYPERTENSION; DIABETES MELLITUS; ATHEROSCLEROSIS; and other CARDIOVASCULAR DISEASES.Carotid Arteries: Either of the two principal arteries on both sides of the neck that supply blood to the head and neck; each divides into two branches, the internal carotid artery and the external carotid artery.Blood Flow Velocity: A value equal to the total volume flow divided by the cross-sectional area of the vascular bed.Orbit: Bony cavity that holds the eyeball and its associated tissues and appendages.Cerebral Arteries: The arterial blood vessels supplying the CEREBRUM.Renal Artery: A branch of the abdominal aorta which supplies the kidneys, adrenal glands and ureters.Femoral Artery: The main artery of the thigh, a continuation of the external iliac artery.Regional Blood Flow: The flow of BLOOD through or around an organ or region of the body.Mesenteric Arteries: Arteries which arise from the abdominal aorta and distribute to most of the intestines.Carotid Artery Diseases: Pathological conditions involving the CAROTID ARTERIES, including the common, internal, and external carotid arteries. ATHEROSCLEROSIS and TRAUMA are relatively frequent causes of carotid artery pathology.Carotid Artery, Internal: Branch of the common carotid artery which supplies the anterior part of the brain, the eye and its appendages, the forehead and nose.Basilar Artery: The artery formed by the union of the right and left vertebral arteries; it runs from the lower to the upper border of the pons, where it bifurcates into the two posterior cerebral arteries.Blindness: The inability to see or the loss or absence of perception of visual stimuli. This condition may be the result of EYE DISEASES; OPTIC NERVE DISEASES; OPTIC CHIASM diseases; or BRAIN DISEASES affecting the VISUAL PATHWAYS or OCCIPITAL LOBE.Amaurosis Fugax: Transient complete or partial monocular blindness due to retinal ischemia. This may be caused by emboli from the CAROTID ARTERY (usually in association with CAROTID STENOSIS) and other locations that enter the central RETINAL ARTERY. (From Adams et al., Principles of Neurology, 6th ed, p245)Arterial Occlusive Diseases: Pathological processes which result in the partial or complete obstruction of ARTERIES. They are characterized by greatly reduced or absence of blood flow through these vessels. They are also known as arterial insufficiency.Carotid Artery, External: Branch of the common carotid artery which supplies the exterior of the head, the face, and the greater part of the neck.Intraocular Pressure: The pressure of the fluids in the eye.Laser-Doppler Flowmetry: A method of non-invasive, continuous measurement of MICROCIRCULATION. The technique is based on the values of the DOPPLER EFFECT of low-power laser light scattered randomly by static structures and moving tissue particulates.Ganglionectomy: Removal of an autonomic or sensory ganglion by any means.Glaucoma, Neovascular: A form of secondary glaucoma which develops as a consequence of another ocular disease and is attributed to the forming of new vessels in the angle of the anterior chamber.Iliac Artery: Either of two large arteries originating from the abdominal aorta; they supply blood to the pelvis, abdominal wall and legs.Visual Acuity: Clarity or sharpness of OCULAR VISION or the ability of the eye to see fine details. Visual acuity depends on the functions of RETINA, neuronal transmission, and the interpretative ability of the brain. Normal visual acuity is expressed as 20/20 indicating that one can see at 20 feet what should normally be seen at that distance. Visual acuity can also be influenced by brightness, color, and contrast.Vertebral Artery: The first branch of the SUBCLAVIAN ARTERY with distribution to muscles of the NECK; VERTEBRAE; SPINAL CORD; CEREBELLUM; and interior of the CEREBRUM.Coronary Artery Bypass: Surgical therapy of ischemic coronary artery disease achieved by grafting a section of saphenous vein, internal mammary artery, or other substitute between the aorta and the obstructed coronary artery distal to the obstructive lesion.Optic Disk: The portion of the optic nerve seen in the fundus with the ophthalmoscope. It is formed by the meeting of all the retinal ganglion cell axons as they enter the optic nerve.Eye: The organ of sight constituting a pair of globular organs made up of a three-layered roughly spherical structure specialized for receiving and responding to light.Radial Artery: The direct continuation of the brachial trunk, originating at the bifurcation of the brachial artery opposite the neck of the radius. Its branches may be divided into three groups corresponding to the three regions in which the vessel is situated, the forearm, wrist, and hand.Sneddon Syndrome: A systemic non-inflammatory arteriopathy primarily of middle-aged females characterized by the association of livedo reticularis, multiple thrombotic CEREBRAL INFARCTION; CORONARY DISEASE, and HYPERTENSION. Elevation of antiphospholipid antibody titers (see also ANTIPHOSPHOLIPID SYNDROME), cardiac valvulopathy, ISCHEMIC ATTACK, TRANSIENT; SEIZURES; DEMENTIA; and chronic ischemia of the extremities may also occur. Pathologic examination of affected arteries reveals non-inflammatory adventitial fibrosis, thrombosis, and changes in the media. (From Jablonski, Dictionary of Syndromes & Eponymic Diseases, 2d ed; Adams et al., Principles of Neurology, 6th ed, p861; Arch Neurol 1997 Jan;54(1):53-60)Mammary Arteries: Arteries originating from the subclavian or axillary arteries and distributing to the anterior thoracic wall, mediastinal structures, diaphragm, pectoral muscles and mammary gland.Myography: The recording of muscular movements. The apparatus is called a myograph, the record or tracing, a myogram. (From Stedman, 25th ed)Subclavian Artery: Artery arising from the brachiocephalic trunk on the right side and from the arch of the aorta on the left side. It distributes to the neck, thoracic wall, spinal cord, brain, meninges, and upper limb.Vasodilation: The physiological widening of BLOOD VESSELS by relaxing the underlying VASCULAR SMOOTH MUSCLE.Paracentesis: A procedure in which fluid is withdrawn from a body cavity or organ via a trocar and cannula, needle, or other hollow instrument.Retinal Neurons: Nerve cells of the RETINA in the pathway of transmitting light signals to the CENTRAL NERVOUS SYSTEM. They include the outer layer of PHOTORECEPTOR CELLS, the intermediate layer of RETINAL BIPOLAR CELLS and AMACRINE CELLS, and the internal layer of RETINAL GANGLION CELLS.Choroid: The thin, highly vascular membrane covering most of the posterior of the eye between the RETINA and SCLERA.Eye Diseases: Diseases affecting the eye.Blood Pressure: PRESSURE of the BLOOD on the ARTERIES and other BLOOD VESSELS.Optic Neuropathy, Ischemic: Ischemic injury to the OPTIC NERVE which usually affects the OPTIC DISK (optic neuropathy, anterior ischemic) and less frequently the retrobulbar portion of the nerve (optic neuropathy, posterior ischemic). The injury results from occlusion of arterial blood supply which may result from TEMPORAL ARTERITIS; ATHEROSCLEROSIS; COLLAGEN DISEASES; EMBOLISM; DIABETES MELLITUS; and other conditions. The disease primarily occurs in the sixth decade or later and presents with the sudden onset of painless and usually severe monocular visual loss. Anterior ischemic optic neuropathy also features optic disk edema with microhemorrhages. The optic disk appears normal in posterior ischemic optic neuropathy. (Glaser, Neuro-Ophthalmology, 2nd ed, p135)Retina: The ten-layered nervous tissue membrane of the eye. It is continuous with the OPTIC NERVE and receives images of external objects and transmits visual impulses to the brain. Its outer surface is in contact with the CHOROID and the inner surface with the VITREOUS BODY. The outer-most layer is pigmented, whereas the inner nine layers are transparent.Splenic Artery: The largest branch of the celiac trunk with distribution to the spleen, pancreas, stomach and greater omentum.Brachial Artery: The continuation of the axillary artery; it branches into the radial and ulnar arteries.Methyldopa: An alpha-2 adrenergic agonist that has both central and peripheral nervous system effects. Its primary clinical use is as an antihypertensive agent.Eisenmenger Complex: A condition associated with VENTRICULAR SEPTAL DEFECT and other congenital heart defects that allow the mixing of pulmonary and systemic circulation, increase blood flow into the lung, and subsequent responses to low oxygen in blood. This complex is characterized by progressive PULMONARY HYPERTENSION; HYPERTROPHY of the RIGHT VENTRICLE; CYANOSIS; and ERYTHROCYTOSIS.Vasoconstriction: The physiological narrowing of BLOOD VESSELS by contraction of the VASCULAR SMOOTH MUSCLE.Hepatic Artery: A branch of the celiac artery that distributes to the stomach, pancreas, duodenum, liver, gallbladder, and greater omentum.Carotid Artery, Common: The two principal arteries supplying the structures of the head and neck. They ascend in the neck, one on each side, and at the level of the upper border of the thyroid cartilage, each divides into two branches, the external (CAROTID ARTERY, EXTERNAL) and internal (CAROTID ARTERY, INTERNAL) carotid arteries.Muscle, Smooth, Vascular: The nonstriated involuntary muscle tissue of blood vessels.Coronary Vessels: The veins and arteries of the HEART.Embolism: Blocking of a blood vessel by an embolus which can be a blood clot or other undissolved material in the blood stream.Celiac Artery: The arterial trunk that arises from the abdominal aorta and after a short course divides into the left gastric, common hepatic and splenic arteries.Endothelium, Vascular: Single pavement layer of cells which line the luminal surface of the entire vascular system and regulate the transport of macromolecules and blood components.Vasodilator Agents: Drugs used to cause dilation of the blood vessels.Nitroarginine: An inhibitor of nitric oxide synthetase which has been shown to prevent glutamate toxicity. Nitroarginine has been experimentally tested for its ability to prevent ammonia toxicity and ammonia-induced alterations in brain energy and ammonia metabolites. (Neurochem Res 1995:200(4):451-6)Mesenteric Artery, Superior: A large vessel supplying the whole length of the small intestine except the superior part of the duodenum. It also supplies the cecum and the ascending part of the colon and about half the transverse part of the colon. It arises from the anterior surface of the aorta below the celiac artery at the level of the first lumbar vertebra.Carotid Stenosis: Narrowing or stricture of any part of the CAROTID ARTERIES, most often due to atherosclerotic plaque formation. Ulcerations may form in atherosclerotic plaques and induce THROMBUS formation. Platelet or cholesterol emboli may arise from stenotic carotid lesions and induce a TRANSIENT ISCHEMIC ATTACK; CEREBROVASCULAR ACCIDENT; or temporary blindness (AMAUROSIS FUGAX). (From Adams et al., Principles of Neurology, 6th ed, pp 822-3)Umbilical Arteries: Specialized arterial vessels in the umbilical cord. They carry waste and deoxygenated blood from the FETUS to the mother via the PLACENTA. In humans, there are usually two umbilical arteries but sometimes one.Ophthalmoscopy: Examination of the interior of the eye with an ophthalmoscope.Middle Cerebral Artery: The largest of the cerebral arteries. It trifurcates into temporal, frontal, and parietal branches supplying blood to most of the parenchyma of these lobes in the CEREBRAL CORTEX. These are the areas involved in motor, sensory, and speech activities.Renal Artery Obstruction: Narrowing or occlusion of the RENAL ARTERY or arteries. It is due usually to ATHEROSCLEROSIS; FIBROMUSCULAR DYSPLASIA; THROMBOSIS; EMBOLISM, or external pressure. The reduced renal perfusion can lead to renovascular hypertension (HYPERTENSION, RENOVASCULAR).Glaucoma, Open-Angle: Glaucoma in which the angle of the anterior chamber is open and the trabecular meshwork does not encroach on the base of the iris.Thoracic Arteries: Arteries originating from the subclavian or axillary arteries and distributing to the anterior thoracic wall, mediastinal structures, diaphragm, pectoral muscles, mammary gland and the axillary aspect of the chest wall.Prospective Studies: Observation of a population for a sufficient number of persons over a sufficient number of years to generate incidence or mortality rates subsequent to the selection of the study group.Temporal Arteries: Arteries arising from the external carotid or the maxillary artery and distributing to the temporal region.Retrospective Studies: Studies used to test etiologic hypotheses in which inferences about an exposure to putative causal factors are derived from data relating to characteristics of persons under study or to events or experiences in their past. The essential feature is that some of the persons under study have the disease or outcome of interest and their characteristics are compared with those of unaffected persons.Glaucoma: An ocular disease, occurring in many forms, having as its primary characteristics an unstable or a sustained increase in the intraocular pressure which the eye cannot withstand without damage to its structure or impairment of its function. The consequences of the increased pressure may be manifested in a variety of symptoms, depending upon type and severity, such as excavation of the optic disk, hardness of the eyeball, corneal anesthesia, reduced visual acuity, seeing of colored halos around lights, disturbed dark adaptation, visual field defects, and headaches. (Dictionary of Visual Science, 4th ed)Muscle Relaxation: That phase of a muscle twitch during which a muscle returns to a resting position.Bronchial Arteries: Left bronchial arteries arise from the thoracic aorta, the right from the first aortic intercostal or the upper left bronchial artery; they supply the bronchi and the lower trachea.Fibrinolytic Agents: Fibrinolysin or agents that convert plasminogen to FIBRINOLYSIN.Treatment Outcome: Evaluation undertaken to assess the results or consequences of management and procedures used in combating disease in order to determine the efficacy, effectiveness, safety, and practicability of these interventions in individual cases or series.Popliteal Artery: The continuation of the femoral artery coursing through the popliteal fossa; it divides into the anterior and posterior tibial arteries.Ulnar Artery: The larger of the two terminal branches of the brachial artery, beginning about one centimeter distal to the bend of the elbow. Like the RADIAL ARTERY, its branches may be divided into three groups corresponding to their locations in the forearm, wrist, and hand.Injections: Introduction of substances into the body using a needle and syringe.Follow-Up Studies: Studies in which individuals or populations are followed to assess the outcome of exposures, procedures, or effects of a characteristic, e.g., occurrence of disease.Vision Disorders: Visual impairments limiting one or more of the basic functions of the eye: visual acuity, dark adaptation, color vision, or peripheral vision. These may result from EYE DISEASES; OPTIC NERVE DISEASES; VISUAL PATHWAY diseases; OCCIPITAL LOBE diseases; OCULAR MOTILITY DISORDERS; and other conditions (From Newell, Ophthalmology: Principles and Concepts, 7th ed, p132).Uterine Artery: A branch arising from the internal iliac artery in females, that supplies blood to the uterus.Electroretinography: Recording of electric potentials in the retina after stimulation by light.Optic Nerve: The 2nd cranial nerve which conveys visual information from the RETINA to the brain. The nerve carries the axons of the RETINAL GANGLION CELLS which sort at the OPTIC CHIASM and continue via the OPTIC TRACTS to the brain. The largest projection is to the lateral geniculate nuclei; other targets include the SUPERIOR COLLICULI and the SUPRACHIASMATIC NUCLEI. Though known as the second cranial nerve, it is considered part of the CENTRAL NERVOUS SYSTEM.