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Drugs and diseases reference index

Drugs and diseases reference index
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Medical Dictionary Definitions A-Z List

Medical Dictionary Definitions A - Z - «V»:

  1. Visual acuity Visual acuity
    Visual acuity: The clarity or clearness of the vision, a measure of how well a person sees. The ability to distinguish details and shapes of objects; also called central vision. The word "acuity" comes from the Latin "acuitas" = sharpness....
  2. Visual acuity test Visual acuity test
    Visual acuity test: This test measures how well you see at various distances. It is the familiar eye chart test. The eye chart itself -- the usual one is called Snellen's chart -- is imprinted with block letters that line-by-line decrease in size, corresponding to the distance at which that line o...
  3. Visual contrast sensitivity Visual contrast sensitivity
    Visual contrast sensitivity: The ability to perceive differences between an object and its background....
  4. Visual evoked response Visual evoked response
    Visual evoked response: VER. A type of electrophysiologic retinal testing done to measure the electrical potential resulting from a visual stimulus....
  5. Visual field Visual field
    Visual field: The entire area that can be seen when the eye is directed forward, including that which is seen with peripheral vision. The visual field can be tested to measure the extent and distribution of the field of vision. The test may be done by a number of methods including what are terme...
  6. Visual field test Visual field test
    Visual field test: A test which measures the extent and distribution of the field of vision. The visual field test may be done by a number of methods including what are termed confrontation, tangent screen exam and automated perimetry. Although the test may seem tedious, it is not painful or uncomf...
  7. Visual nerve pathways Visual nerve pathways
    Visual nerve pathways: The optic nerves serving the eyes join behind the eyes just in front of the pituitary gland to form a cross-shaped structure called the optic chiasma. Within the optic chiasma some of the nerve fibers cross. The fibers from the nasal (inside) half of each retina cross over, bu...
  8. Visual pathway glioma Visual pathway glioma
    Visual pathway glioma: A slow-growing benign tumor of the eye....
  9. Visual receptor Visual receptor
    Visual receptor: The layer of rods and cones that are the visual cells of the retina....
  10. Vital Vital
    Vital: Necessary to maintain life. Breathing is a vital function....
  11. Vital bodily function Vital bodily function
    Vital bodily function: 1. An essential bodily function. 2. A key function for life. 3. A function required by most, if not all, people. The definition of vital bodily functions is prerequisite to the determination of death. But what are the vital bodily functions? Do they include cerebral function...
  12. Vitamin A Vitamin A
    Vitamin A: Vitamin A is retinol. Carotene compounds (found, for example, in egg yolk, butter and cream) are gradually converted by the body to vitamin A (retinol). A form of vitamin A called retinal is responsible for transmitting light sensation in the retina of the eye. Deficiency of vitamin A...
  13. Vitamin A deficiency Vitamin A deficiency
    Vitamin A deficiency: A lack of vitamin A. Vitamin A deficiency (VAD) occurs where diets contain insufficient vitamin A for meeting the needs associated with growth and development, physiological functions, and periods of added stress due to illness. Infections such as measles may precipitate a c...
  14. Vitamin B -- niacin Vitamin B -- niacin
    Vitamin B -- niacin: Deficiency of niacin, one of the B-complex vitamins, causes pellagra. See: Pellagra....
  15. Vitamin B -- nicotinic acid Vitamin B -- nicotinic acid
    Vitamin B -- nicotinic acid: Deficiency of nicotinic acid (also known as niacin), one of the B-complex vitamins, causes pellagra. Pellagra was known as the "disease of the four D's" -- dermatitis, diarrhea, dementia and death. The disease is specifically characterized by: Dermatitis: A rash on ...