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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 - «O»:

  1. Opioid Opioid
    Opioid: 1. A synthetic narcotic that resembles the naturally occurring opiates. 2. Any substance that binds to or otherwise affects the opiate receptors on the surface of the cell....
  2. Opisthotonos Opisthotonos
    Opisthotonos: A great rigid spasm of the body with the back fully arched and the heels and head bent back. Opisthotonos occurs in meningitis, especially in infants, due to irritation of the membranes surrounding the brain and spinal cord. It also occurs with depressed brain function and injury to th...
  3. Opium Opium
    Opium: An addictive narcotic drug derived from the unripe seedpods of the opium poppy. Preparations of opium were called laudanum. Derivatives of laudanum include paregoric (a drug to treat diarrhea), morphine and heroin. For centuries, opium was used as a painkiller in the Middle and Far East. It...
  4. Opportunistic condition Opportunistic condition
    Opportunistic condition: A condition that occurs especially or exclusively in persons with a weak immune system due, for example, to AIDS, cancer or immunosuppressive drugs, such as corticosteroids or chemotherapy. An opportunistic condition may be an infection, such as toxoplasmosis or cytomega...
  5. Opportunistic infection Opportunistic infection
    Opportunistic infection: An infection that occurs because of a weakened immune system. Opportunistic infections are a particular danger for people with AIDS. The HIV virus itself does not cause death, but the opportunistic infections that occur because of its effect on the immune system can. S...
  6. Opportunistic microorganism Opportunistic microorganism
    Opportunistic microorganism: A bacteria, virus, or fungus that takes advantage of certain opportunities to cause disease. Those opportunities are called opportunistic conditions. These microorganisms are often ones that can lie dormant in body tissues for many years, such as the human herpes vi...
  7. Optic Optic
    Optic: Having to do with vision. ...
  8. Optic cup Optic cup
    Optic cup: The white, cup-like area in the center of the optic disc. The optic disk is the circular area at the back of the inside of the eye where the optic nerve connects to the retina....
  9. Optic disc Optic disc
    Optic disc: The circular area in the back of the inside of the eye where the optic nerve connects to the retina. Also called the optic nerve head....
  10. Optic glioma Optic glioma
    Optic glioma: A benign tumor on an optic nerve or the optic chiasm (the crossing of the two optic nerves). Optic gliomas are derived from glial cells and are classified as low-grade astrocytomas. They cause symptoms both by pressure and by destruction of normal optic nerve tissue. They may result i...
  11. Optic nerve Optic nerve
    Optic nerve: The optic nerve connects the eye to the brain. The optic nerve carries the impulses formed by the retina, the nerve layer that lines the back of the eye and senses light and creates impulses. These impulses are dispatched through the optic nerve to the brain, which interprets them...
  12. Optic nerve head Optic nerve head
    Optic nerve head: The circular area in the back of the inside of the eye where the optic nerve connects to the retina....
  13. Optic nerve pathways Optic nerve pathways
    Optic nerve pathways: The left and right branches of the optic nerves 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 ...
  14. Optic neuroma Optic neuroma
    Optic neuroma: A slow-growing benign tumor of the optic nerve. Optic gliomas are associated with neurofibromatosis type 1 (NF1), can lead to partial or complete loss of vision, painless bulging of the eye, and headache, and are treated by surgical excision (removal) or, if too extensive, by radiothe...
  15. Optician Optician
    Optician: A specialist in fitting eyeglasses and making lenses to correct vision problems. An optometrist performs eye examinations and writes prescriptions for corrective lenses; an optician fills that prescription....