opiates such as cocaineand morphine,
amfetamine drugs, and barbiturate drugs.
controlled trialA method of testing
the effectiveness of new treatments or
comparing different treatments. In a
typical controlled drug trial, 2 compara-
ble groups of patients suffering from
the same illness are given courses of
apparently identical treatment. However,
only one group receives the new treat-
ment; the second control group is given
a placebo. Alternatively, the control group
may be given an established drug that
is already known to be effective. After a
predetermined period, the 2 groups are
assessed medically. Controlled trials must
be conducted “blind’’ (the patients do not
know which treatment they are receiving).
In a “double-blind’’ trial, neither the pa-
tients nor the doctors who assess them
know who is receiving which treatment.
contusionBruising to the skin and
underlying tissues from an injury.
convalescenceThe recovery period fol-
lowing an illness or surgery during
which the patient regains strength
before returning to normal activities.
conversion disorderA psychological
disorder in which repressed emotions
appear to be unconsciously converted
into physical symptoms such as blind-
ness, loss of speech, or paralysis. The
condition, formerly known as hysteria,
is generally treated with psychotherapy.
convulsionSee seizure.
convulsion, febrileTwitching or jerking
of the limbs with loss of consciousness
that occurs in a child after a rapid rise
in temperature. Febrile convulsions are
common, usually affecting children be-
tween the ages of 6 months and 5 years.
Convulsions are caused by an immaturity
of the temperature-lowering mechanism
in the brain, allowing the temperature to
rise too rapidly in response to infections
such as measlesor influenza. Treatment
aims to lower the temperature by spong-
ing the child’s face and body with tepid
water and using a fan. Seizures can often
be prevented in susceptible children by
giving paracetamolat the first signs of
fever. Most children who have seizures
suffer no ill effects. The risk of developing
epilepsyis very small but is increased in
children with a pre-existing abnormality
of the brain or nervous system, or chil-
dren with a family history of epilepsy.
Cooley’s anaemiaSee thalassaemia.
COPD The abbreviation for chronic
obstructive pulmonary disease (see pul-
monary disease, chronic obstructive).
copperA metallic element that is an
essential part of several enzymes. Cop-
per is needed by the body only in
minute amounts (see trace elements).
Copper excess may result from the rare
inherited disorder Wilson’s disease.
co-proxamolAn analgesic drug con-
taining paracetamoland the weak opioid
analgesic dextropropoxyphene, widely
used to relieve mild to moderate pain
that has not responded to paracetamol
or other nonopioid analgesics alone. Side
effects are dizziness, drowsiness, con-
stipation, and nausea. The drug may be
habit-forming if taken over a long period.
cordotomyAn operation to divide bun-
dles of nerve fibres within the spinal
cordto relieve persistent pain that has
not responded to other treatment. Cor-
dotomy is most frequently performed
for pain in the lower trunk and legs,
especially in people with cancer.
cornA small area of thickened skin on a
toe, caused by the pressure of a tight-
fitting shoe. Treatment is with a spongy
ring or corn pad to ease the pressure on
the corn, or the thickened skin can be
removed by a chiropodist.
corneaThe transparent thin-walled dome
that forms the front of the eyeball. The
cornea is joined at its circumference to
the sclera(white of the eye); the black
pupil and the coloured iris are visible
beneath it. The main functions of the
cornea are to help focus light-rays on toCONTROLLED TRIAL CORNEA
C
CORNEAIrisLensConjunctivaCorneaRetina