Medications

Vitamin B12: A vitamin important for the normal formation of red blood cells and the health of the nerve tissues. Undetected and untreated vitamin B12 deficiency can lead to anemia and permanent nerve and brain damage. Pernicious anemia is a...

Vitamin B1 deficiency, infantile - Medical

Vitamin B1 deficiency, infantile: See: Infantile beriberi.Last Editorial Review: 11/18/2003Infantile beriberi: Disease in infants due to deficiency of thiamine. This disease is well-known in undeveloped countries among malnourished infants but it i...

Vitamin B1 - Medical

Vitamin B1: Thiamine. Vitamin B1 (thiamine) acts as a coenzyme in the metabolism of the body. Deficiency of thiamine leads to the disease beriberi, a disease affecting the heart and nervous system. The word "vitamin" was coined in 1911 by the W...

Vitamin B -- pantothenic acid - Medical

Vitamin B -- pantothenic acid: This is one of the less well known B vitamins, perhaps because it is widely distributed in nature. Pantothenic acid is virtually ubiquitous. It is present in foods as diverse as poultry, soybeans, yogurt, and sweet pot...

Vitamin B -- nicotinic acid - Medical

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 sp...

Vitamin B -- niacin - Medical

Vitamin B -- niacin: Deficiency of niacin, one of the B-complex vitamins, causes pellagra. See: Pellagra. Last Editorial Review: 8/12/2003Pellagra: A disease due to deficiency of niacin, a B-complex vitamin. Pellagra is the "disease of the four...

Vitamin A deficiency - Medical

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 i...

Vitamin A - Medical

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 sensati...

Vital bodily function - Medical

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 vita...

Vital - Medical

Vital: Necessary to maintain life. Breathing is a vital function.Last Editorial Review: 4/27/2011 5:27:15 PM...

Visual receptor - Medical

Visual receptor: The layer of rods and cones that are the visual cells of the retina.Last Editorial Review: 11/30/1999 7:50:00 PM...

Visual pathway glioma - Medical

Visual pathway glioma: A slow-growing benign tumor of the eye. Last Editorial Review: 1/10/2003...

Visual nerve pathways - Medical

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 th...

Visual field test - Medical

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 th...

Visual field - Medical

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...

Visual evoked response - Medical

Visual evoked response: VER. A type of electrophysiologic retinal testing done to measure the electrical potential resulting from a visual stimulus. Last Editorial Review: 4/18/2004 Electrophysiologic retinal testing: Testing done to diagnose speci...

Visual contrast sensitivity - Medical

Visual contrast sensitivity: The ability to perceive differences between an object and its background.Last Editorial Review: 9/24/1999 9:03:00 AM...

Visual acuity test - Medical

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,...

Visual acuity - Medical

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. Last...

Vision, tunnel - Medical

Vision, tunnel: See: Tunnel vision.Last Editorial Review: 10/1/2003 Tunnel vision: Loss of peripheral vision with retention of central vision, resulting in a constricted circular tunnel-like field of vision. And, by extension, any very narrow point...

Vision, tubular - Medical

Vision, tubular: See: Tubular vision; Tunnel vision. Last Editorial Review: 10/1/2003 Tubular vision: A centrally constricted field of vision that is like what you can see through a tube. Also called tunnel vision. See: Tunnel vision.Last Editori...

Vision, peripheral - Medical

Vision, peripheral: See: Peripheral vision. Last Editorial Review: 10/1/2003 Peripheral vision: Side vision. The ability to see objects and movement outside of the direct line of vision. Peripheral vision is the work of the rods, nerve cells loca...

Vision, macular - Medical

Vision, macular: The macula is a special area in the center of the retina, the light-sensitive layer of tissue at the back of the eye. As we read, light is focused onto our macula. There, millions of cells change the light into nerve signals that tel...

Vision, low - Medical

Vision, low: Visual loss that cannot be corrected with eyeglasses or contact lenses and that interferes with daily living activities.Last Editorial Review: 9/26/1999 7:27:00 PM...

Vision, central - Medical

Vision, central: See: Central vision.Last Editorial Review: 4/27/2011 5:27:15 PM Central vision: Straight-ahead vision. Central vision is the work of the macula, a small area in the center of the retina that contains a rich collection of cones. (The...

Vision, blurred - Medical

Vision, blurred: See: Blurred vision.Last Editorial Review: 1/14/2004 Blurred vision: Lack of sharpness of vision with, as a result, the inability to see fine detail. Blurred vision can occur when a person who wears corrective lens is without them....

Vision, binocular - Medical

Vision, binocular: See: Binocular vision.Last Editorial Review: 5/5/2003 Binocular vision: The ability to maintain visual focus on an object with both eyes, creating a single visual image. Lack of binocular vision is normal in infants. Adults...

Vision therapy - Medical

Vision therapy: The use of special eye exercises to address eye defects, such as strabismus. Some vision therapists also claim that eye exercises can help people with neurological or learning disabilities. This approach is not proven for the ...

Viscus - Medical

Viscus: An internal organ of the body, specifically one within the chest (as the heart or lungs) or abdomen (as the liver, pancreas or intestines). "Viscus" is the Latin word for "an organ of the body." The plural of "viscus" is "viscera."Last Edito...

Visceral pericardium - Medical

Visceral pericardium: The inner layer of the pericardium, a conical sac of fibrous tissue that surrounds the heart and the roots of the great blood vessels. The pericardium has outer and inner coats. The outer coat is tough and thickened, loo...