Medical Dictionary Definitions A-Z List
Medical Dictionary Definitions A - Z - «P»:
Photocoagulation: The coagulation (clotting) of tissue using a laser which produces light in the visible green wavelength that is selectively absorbed by hemoglobin, the pigment in red blood cells, in order to seal off bleeding blood vessels.
Photocoagulation has diverse uses such as, for example, ...
Photodynamic therapy: A form of cancer treatment using an photosensitizing agent administered intravenously which concentrates selectively in tumor cells, followed by exposure of the tumor tissue to a special red laser light, in order to destroy as much of the tumor as possible.
Photokeratitis: A burn of the cornea (the clear front surface of the eye) by ultraviolet B rays (UVB). Also called radiation keratitis or snowblindness.
The condition typically occurs at high altitudes on highly reflective snow fields or, less often, with a solar eclipse. Artificial sources of UVB ...
Photophobia: Painful oversensitivity to
light. For example, there is photophobia in measles (rubeola).
Keeping the lights dim or the room darkened may be useful. Sunglasses
may also help.
Whereas most phobias are abnormal, excessive, and irrational,
Photophobia is usually an appropriate rational...
Photorefractive keratectomy (PRK)
Photorefractive keratectomy (PRK): A kind of
laser eye surgery designed to
change the shape of the cornea to eliminate (or reduce) the
need for glasses
and contact lenses. The laser is used to remove the outer
layer of the
and flatten the cornea. The flattening of the cornea is
Photosensitivity: In medicine, increased sensitivity of the skin to light and other sources of UV.
Photosensitivity commonly causes reddening
and blistering of the skin with
exposure to sunlight and, in time, it heightens the risk of skin cancer.
A number of diseases make for photosensitivity, as ...
Phototherapy: Treatment with light. For example, a newborn with
jaundice may be "put under the lights." ...
Phrenic pacing: See: Diaphragm pacing....
Phrenology: The study of variations in size, shape, and proportion of the cranium. Phrenology was a pseudoscience of the 18th and 19th centuries based on the belief that a person's character could be learned by looking with care at the shape of their head and noting each and every bump and depressio...
PHS:The Public Health Service, the agency responsible for the public health of the American people. The Public Health Service (PHS) administers a number of critically important health agencies including the Food and Drug Administration (FDA), the Centers for Disease Control (CDC), and the National I...
Phthisis: A good trivia or crossword item. An over-consonanted Greek word meaning "a dwindling or wasting away." Pronounced TIE-sis.
Phthisis is an archaic name for tuberculosis. A person afflicted with tuberculosis in the old days was destined to dwindle and waste away like Mimi, the heroine of P...
Phylogenetics: The study of the relationships between organisms based on how closely they are related to each other. In phylogenetics, the most convenient way of visually presenting evolutionary relationships among a group of organisms is through illustrations called phylogenetic trees. See also: Mo...
Physiatrist: A physician specializing in physical
medicine and rehabilitation. Physiatrists specialize in restoring optimal function to
people with injuries to the muscles, bones, tissues, and nervous system (such as stroke
Physical child abuse
Physical child abuse: Next to child neglect, physical abuse
is the second most frequently reported form of child abuse,
accounting for 25% of all cases of child abuse.
Physical child abuse is physical injury inflicted upon the child
with cruel and/or malicious intent. Physical abuse can be the ...
Physical growth: See: Normal growth....