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Arteriovenous Nicking
Arteriovenous nicking, also known as AV nicking, is the phenomenon where, on examination of the eye, a small artery (arteriole) is seen crossing a small vein (venule), which results in the compression of the vein with bulging on either side of the crossing. This is most commonly seen in eye disease caused by high blood pressure (hypertensive retinopathy). It is thought that, since the arteriole and venule share a common sheath, the arteriole's thicker walls push against those of the venule forcing the venule to collapse. This makes the venule form an hourglass shape around the arteriole. Other theories suggest that this results not from compression from the arteriole but from sclerotic thickening or glial cell proliferation at the site where the two vessels cross. Signs: #Gunn Gunn may refer to: Places * Gunn City, Missouri, a village * Gunn, Northern Territory, outer suburb of Darwin * Gunn, Alberta, Canada, a hamlet * Gunn Valley, a mountain valley in British Colum ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retina
The retina (; or retinas) is the innermost, photosensitivity, light-sensitive layer of tissue (biology), tissue of the eye of most vertebrates and some Mollusca, molluscs. The optics of the eye create a focus (optics), focused two-dimensional image of the visual world on the retina, which then processes that image within the retina and sends nerve impulses along the optic nerve to the visual cortex to create visual perception. The retina serves a function which is in many ways analogous to that of the photographic film, film or image sensor in a camera. The neural retina consists of several layers of neurons interconnected by Chemical synapse, synapses and is supported by an outer layer of pigmented epithelial cells. The primary light-sensing cells in the retina are the photoreceptor cells, which are of two types: rod cell, rods and cone cell, cones. Rods function mainly in dim light and provide monochromatic vision. Cones function in well-lit conditions and are responsible fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fundoscopy
Ophthalmoscopy, also called funduscopy, is a test that allows a health professional to see inside the fundus of the eye and other structures using an ophthalmoscope (or funduscope). It is done as part of an eye examination and may be done as part of a routine physical examination. It is crucial in determining the health of the retina, optic disc, and vitreous humor. The pupil is a hole through which the eye's interior can be viewed. For better viewing, the pupil can be opened wider (dilated; mydriasis) before ophthalmoscopy using medicated eye drops (dilated fundus examination). However, undilated examination is more convenient (albeit not as comprehensive), and is the most common type in primary care. An alternative or complement to ophthalmoscopy is to perform a fundus photography, where the image can be analysed later by a professional. Types There are two major types of ophthalmoscopy: * direct ophthalmoscopy, which produces an upright (unreversed) image of approximately ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arteriole
An arteriole is a small-diameter blood vessel in the microcirculation that extends and branches out from an artery and leads to capillary, capillaries. Arterioles have vascular smooth muscle, muscular walls (usually only one to two layers of smooth muscle cells) and are the primary site of vascular resistance. The greatest change in blood pressure and velocity of blood flow occurs at the transition of arterioles to capillaries. This function is extremely important because it prevents the thin, one-layer capillaries from exploding upon pressure. The arterioles achieve this decrease in pressure, as they are the site with the highest resistance (a large contributor to total peripheral resistance) which translates to a large decrease in the pressure. Structure In a healthy vascular system, the endothelium lines all blood-contacting surfaces, including arteries, arterioles, veins, venules, capillaries, and heart chambers. This healthy condition is promoted by the ample production of n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Venule
A venule is a very small vein in the microcirculation that allows blood to return from the capillary beds to drain into the venous system via increasingly larger veins. Post-capillary venules are the smallest of the veins with a diameter of between 10 and 30 micrometres (μm). When the post-capillary venules increase in diameter to 50μm they can incorporate smooth muscle and are known as muscular venules. Veins contain approximately 70% of total blood volume, while about 25% is contained in the venules. Many venules unite to form a vein. Structure Post-capillary venules have a single layer of endothelium surrounded by a basal lamina. Their size is between 10 and 30 micrometers and are too small to contain smooth muscle. They are instead supported by pericytes that wrap around them. When the post-capillary venules increase in diameter to 50μm they can incorporate smooth muscle and are known as muscular venules. They have an inner endothelium composed of squamous endothe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
High Blood Pressure
Hypertension, also known as high blood pressure, is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms itself. It is, however, a major risk factor for stroke, coronary artery disease, heart failure, atrial fibrillation, peripheral arterial disease, vision loss, chronic kidney disease, and dementia. Hypertension is a major cause of premature death worldwide. High blood pressure is classified as primary (essential) hypertension or secondary hypertension. About 90–95% of cases are primary, defined as high blood pressure due to non-specific lifestyle and genetic factors. Lifestyle factors that increase the risk include excess salt in the diet, excess body weight, smoking, physical inactivity and alcohol use. The remaining 5–10% of cases are categorized as secondary hypertension, defined as high blood pressure due to a clearly identifiable cause, such as chronic ki ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hypertensive Retinopathy
Hypertensive retinopathy is damage to the retina and retinal circulation due to high blood pressure (i.e. hypertension). Signs and symptoms Most patients with hypertensive retinopathy have no symptoms. However, some may report decreased or blurred vision, and headaches. Signs Signs of damage to the retina caused by hypertension include: * Arteriolar changes, such as generalized arteriolar narrowing, focal arteriolar narrowing, arteriovenous nicking, changes in the arteriolar wall (arteriosclerosis) and abnormalities at points where arterioles and venules cross. Manifestations of these changes include ''Copper wire arterioles'' where the central light reflex occupies most of the width of the arteriole and ''Silver wire arterioles'' where the central light reflex occupies all of the width of the arteriole, and "arterio-venular (AV) nicking" or "AV nipping", due to venous constriction and banking. * Advanced retinopathy lesions, such as microaneurysms, blot hemorrhages and/or flam ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sclerosis (medicine)
Sclerosis () is the stiffening of a tissue or anatomical feature, usually caused by a replacement of the normal organ-specific tissue with connective tissue. The structure may be said to have undergone sclerotic changes or display sclerotic lesions, which refers to the process of sclerosis. Common medical conditions whose pathology involves sclerosis include: * Amyotrophic lateral sclerosis—also known as Lou Gehrig's disease or motor neurone disease—a progressive, incurable, usually fatal disease of motor neurons. * Atherosclerosis, a deposit of fatty materials, such as cholesterol, in the arteries which causes hardening. * Focal segmental glomerulosclerosis is a disease that attacks the kidney's filtering system ( glomeruli) causing serious scarring and thus a cause of nephrotic syndrome in children and adolescents, as well as an important cause of kidney failure in adults. * Hippocampal sclerosis, a brain damage often seen in individuals with temporal lobe epilepsy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glial Cell
Glia, also called glial cells (gliocytes) or neuroglia, are non-neuronal cells in the central nervous system (the brain and the spinal cord) and in the peripheral nervous system that do not produce electrical impulses. The neuroglia make up more than one half the volume of neural tissue in the human body. They maintain homeostasis, form myelin, and provide support and protection for neurons. In the central nervous system, glial cells include oligodendrocytes (that produce myelin), astrocytes, ependymal cells and microglia, and in the peripheral nervous system they include Schwann cells (that produce myelin), and satellite cells. Function They have four main functions: * to surround neurons and hold them in place * to supply nutrients and oxygen to neurons * to insulate one neuron from another * to destroy pathogens and remove dead neurons. They also play a role in neurotransmission and synaptic connections, and in physiological processes such as breathing. While glia w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Robert Marcus Gunn
Robert Marcus Gunn (1850, Dunnet – 29 November 1909, Hindhead) was a Scotland, Scottish ophthalmologist remembered for AV nicking, Gunn's sign and the Marcus Gunn pupil. Early life and education Gunn went to school in Golspie, then studied medicine at the University of St Andrews and the University of Edinburgh, graduating with distinction Master of Arts (Scotland), M.A. in 1871 and Bachelor of Medicine, Bachelor of Surgery, M.B.,C.M. in 1873. He was influenced by James Syme, Joseph Lister, 1st Baron Lister, Joseph Lister and Douglas Argyll Robertson during his studies. He taught himself direct ophthalmoscopy, a skill for which he would later become particularly noted. Career Gunn was a Pre-registration house officer, house physician at Moorfields Eye Hospital and then worked in comparative anatomy at University College Hospital. He worked at the Perth District Asylum during the summers of 1874 and 1875, where he examined the fundus (eye), fundi of all the patients. He ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
