CONTACT LENSES
TYPES AND SYMPTOMS
There are two common types: infective
conjunctivitis,
caused by bacteria or
viruses; and allergic conjunctivitis, an
allergic response to substances such as
cosmetics and pollen. Both types may
have
sim ilar
symptoms.
In
infective
conjunctivitis, the discharge contains
pus and may result in the eyelids being
stuck together on waking in the m orn-
ings.
In
allergic
conjunctivitis,
the
discharge is clear and the eyelids are
often swollen and itchy.
Other forms of conjunctivitis that
occur less commonly include neonatal
ophthalmia
(infective
eye
disease
in
newborns),
keratoconjunctivitis
(inflam -
mation of both the conjunctiva and the
cornea), and
trachoma
(a serious form
of chlamydial infection).
TREATMENT
Bacterial infections
are
treated with
eyedrops or ointment containing an
antibiotic drug.
Viral conjunctivitis often
disappears without the need for treat-
ment. Allergic conjunctivitis may be
treated with eyedrops that contain cro-
moglicate,
an
antihistamine,
or
a
corticosteroid drug.
connective tissue
The material that supports, binds, or
separates the various structures of the
body.
Tendons
and
cartilage
are made up
of connective tissue. This type of tissue
also forms the matrix (basic substance)
of
bone
and the nonmuscular structures
of
arteries
and
veins.
connective tissue diseases
Certain
autoimmune disorders
(disorders
in w hich the immune system attacks
the
body’s
own
tissues)
that
often
affect blood vessels and produce sec-
ondary
damage
to
connective tissue
.
Connective
tissue
diseases
include
rheumatoid arthritis
,
polyarteritis nodosa
,
systemic
lupus erythematosus
,
systemic
sclerosis
,
and
dermatomyositis
.
Conn’s syndrome
A disorder caused by the secretion of
excessive
amounts
of the
hormone
aldosterone
.
The overproduction of this
hormone is caused by a noncancerous
tumour of one of the
adrenal glands
.
(See also
aldosteronism
. )
consciousness
A state of alertness in w hich a person is
fully aware of his or her thoughts, sur-
roundings, and intentions.
consent
Also sometimes referred to as informed
consent, the legal term describing a
patient’s agreement to a doctor per-
form ing an operation, arranging drug
treatment, or carrying out a diagnostic
test. The patient’s consent is also need-
ed before a doctor supplies confidential
information to an insurance company,
an employer, or a lawyer.
Consent is valid only if the patient
has been fully informed about the pur-
pose of that particular procedure, the
likely outcome, and any complications
and side effects. Consent cannot be
given by young children or by people
w ho are not considered to be com-
petent,
but
a relative
may
give
or
withhold consent on their behalf.
constipation
The infrequent or difficult passing of
hard, dry
faeces
.
Constipation may be
uncomfortable but in the short term is
usually harmless.
CAUSES
The most common cause of constipa-
tion is insufficient fibre in the diet (see
fibre, dietary
) ,
because fibre assists the
propulsion of waste matter through the
colon
.
Other common causes include
lack of regular bowel movements due
to poor toilet-training in childhood or
repeatedly ignoring the urge to move
the
bowels.
Constipation
in
elderly
people may be due to im m obility or to
weakness of the muscles of the abdo-
men and the pelvic floor.
Occasionally, constipation is a symp-
tom of an underlying disorder. This is
especially likely if it is part of a per-
sistent
change
in
bowel
habits
in
someone over the age of
4 0
, or if it is
accompanied by other symptoms such
as blood in the faeces, pain on moving
the bowels, or weight loss. Conditions
that may cause
constipation include
haemorrhoid
s,
anal fissure
,
irritable bowel
syndrome
,
and narrowing of the colon
due to disorders such as
diverticular dis-
ease
or cancer (see
colon, cancer of
) .
TREATMENT
Self-help measures such as establishing
a regular bowel routine, increasing the
amount of fibre in the diet, and drink-
ing more fluids are usually beneficial.
Prolonged use of
laxative drugs
should
be avoided, because this can impair the
normal functioning of the colon.
constriction
A narrowed area in the body, or the
process of narrowing.
consultant
In the UK, a doctor, usually attached to
a certain hospital, w ho is a specialist in
a particular branch of medicine and
w ho takes full responsibility for the
patients in his or her care.
contact dermatitis, allergic
A type of
dermatitis
caused by an aller-
gic skin reaction to a substance that is
harmless for most people.
Common
causes include nickel and rubber. (See
also
irritant dermatitis
. )
contact lenses
Thin, shell-like, transparent discs fitted
over the
cornea
of the eye that are used
to
correct
defective
vision.
Contact
lenses are most commonly used for the
correction of
myopia
(shortsightedness)
and
hypermetropia
(longsightedness). In
addition, noncorrective lenses are avail-
able for cosmetic use, for example to
change eye colour.
TYPES
There are several types. Hard plastic
lenses give good vision; they are also
long-lasting and durable, inexpensive,
and easy to maintain. Sometimes, how-
ever, these lenses are difficult for the
wearers to tolerate and may fall out.
Hard gas-permeable lenses are more
comfortable because they allow oxygen
to pass through to the eye, but are less
durable. Soft lenses are the most com-
fortable because of their high water
C
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