BLEPHAROPLASTY
BLOCKING
blepharoplasty
A cosmetic operation
to remove wrinkled, drooping skin from
the upper and/or lower eyelids.
blepharospasm
Prolonged, involuntary,
contraction of one of the muscles con-
trolling the eyelids, causing them to
close. It may be due to
photophobia,
damage to the
cornea,
or
dystonia,
for
which
botulinum toxin
(a muscle relax-
ant) treatment is highly effective.
blind loop syndrome
A condition in
which a redundant area or dead end
(blind loop) in the small intestine
becomes colonized with bacteria. This
results in abnormal faeces and poor
absorption of nutrients. The syndrome
may result from surgery or a
stricture
(narrowing) in the intestine due to a
disorder such as
Crohn's disease.
It is
characterized by
steatorrhoea
(pale yel-
low, foul-smelling, fatty, bulky faeces
that are difficult to flush away), tired-
ness, and weight loss.
Antibiotic drug
treatment usually cures the condition.
blindness
Inability to see. Definitions
of blindness and partial sight vary. In
the UK, blindness is defined as a cor-
rected
visual acuity
of 3/60 or less in the
better eye, or a
visual field
of no more
than 20 degrees in the better eye. Blind-
ness may result from injury to, or
disease or degeneration of, the eyeball;
the optic nerve or nerve pathways con-
necting the eye to the brain; or the
brain itself. Clouding of the cornea may
result from
Sjogren's syndrome,
vitamin
A deficiency, chemical damage, infec-
tions, and injury.
Corneal ulcers
can
cause blindness due to scarring of the
cornea.
Uveitis
and
cataracts
are other
common causes of blindness.
Diabetes
mellitus
,
hypertension
, or injury can all
cause bleeding into the cavity of the
eyeball and subsequent loss of vision.
Bleeding into the fluid in front of the
lens (
hyphaem a
) or behind the lens
(v
itreous haem orrhage
) can also result
in loss of vision. Other conditions that
may cause blindness include
glaucoma;
retinal artery occlusion
or
retinal vein
occlusion;
age-related
macular degener-
ation; retinopathy; retinal detachment;
tumours such as
retinoblastoma
and
malignant
melanoma
of the eye; and
retinal haem orrhage.
Loss of vision may be due to nerve con-
duction problems. These problems may
be the result of pressure caused by a
tumour; reduced blood supply to the
optic nerve;
optic neuritis
; or toxic or
nutritional deficiencies. Blindness can
result if there is pressure on the visual
cortex from a
brain tumour
or
brain
haem orrhage
, or if the blood supply to
the cortex is reduced following a
stroke.
Treatment depends on the underlying
cause. If the loss of vision cannot be
corrected, the patient may then be reg-
istered as legally blind or partially
sighted. (See also eye;
vision, loss of.)
blind spot
The small, oval-shaped area
on the retina of the eye where the optic
nerve leaves the eyeball. The area is not
sensitive to light because it has no light
receptors (nerve endings responsive to
light). The blind spot can also be used
to describe the part of the
visual field
in
which objects cannot be detected.
blister
A collection of fluid beneath the
outer layer of the skin that forms a
raised area. A blister contains fluid that
has leaked from blood vessels in under-
lying skin layers after minor damage
and protects the damaged tissue. Com-
mon causes are
burns
and friction.
Blisters may also occur with
pem phigus
,
pem phigoid
,
dermatitis herpetiformis
,
some types of
porphyria
, and some skin
diseases. These include
eczema, epider-
molysis bullosa
,
impetigo
, and
erythema
multiforme.
Small blisters develop in
the viral infections
chickenpox
,
herpes
zoster
(shingles), and
herpes simplex
.
Generally, blisters are best left intact,
but large or unexplained blisters need
medical attention.
bloating
Distension of the abdomen,
commonly due to wind in the stomach
or intestine (see
abdominal swelling).
blocked
nose
See
nasal congestion;
nasal obstruction
.
blocking
Inability to express true feel-
ings or thoughts, usually as a result of
emotional or mental conflict. In Freudi-
an- based psychotherapies, blocking is
regarded as originating from repression
of painful emotions in early life. A very
specific form of thought blocking occurs
in
schizophrenia
: trains of thought are
persistently interrupted involuntarily to
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