EYE, ARTIFICIAL
EYE, FOREIGN BODY IN
E
reflex is protective and helps to spread
the tear film evenly over the cornea to
enable clear vision.
eye, artificial
A
prosthesis
to replace an
eye
that has been removed. It is worn
for cosmetic reasons. Some movement
of the artificial eye may be achieved by
attaching the muscles that normally
move the eye to the remaining conjunc-
tival membrane (see
conjunctiva
)
or to a
plastic implant in the eye socket.
eye, disorders of
Many
eye
disorders
are minor, but some can cause loss of
vision unless treated. (See also
cornea,
disorders of
;
retinal detachment
.)
Squint
is sometimes present at birth.
Rarely, babies are born with
microph-
thalmos
. Other
congenital
disorders that
affect the eye are
nystagmus
,
albinism
,
and developmental abnormalities of the
cornea and retina.
Conjunctivitis
is the most common eye
infection and rarely affects vision.
Tra-
choma
or severe bacterial conjunctivitis
can impair vision. Corneal infections
can lead to blurred vision or corneal
perforation
if not treated early. Endoph-
thalmitis (infection within the eye) can
occur as a result of eye injury or infec-
tion elsewhere in the body.
Narrowing, blockage or
inflammation
of the blood vessels of the
retina
may
cause partial or total loss of vision.
Malignant melanoma
of the
choroid
is
the most common cancerous tumour of
the eye.
Retinoblastoma
is a cancerous
tumour of the retina that most com-
monly affects children.
Various
vitamin
deficiencies (particu-
larly of vitamin A) can affect the eye.
This may lead to
xerophthalmia
,
night
blindness
,
or, ultimately,
keratomalacia
.
Uveitis
may be caused by infection or
an
autoimmune disorder
such as
anky-
losing spondylitis
and
sarcoidosis
.
Macular degeneration
of the retina is
common in the elderly, as is
cataract
Glaucoma
, in which the pressure in-
side the eyeball becomes raised, can
lead to permanent loss of vision. In
reti-
nal detachment
, the retina lifts away
from the underlying layer of the eye.
Ametropia is a general term for any
focusing error, such as
astigmatism,
myopia
,
or
hypermetropia
.
Presbyopia
is
the progressive loss with age of the
ability to focus at close range.
Ambly-
opia
is often due to squint.
eye-drops
Medication in solution used
to treat
eye disorders
or to aid in diag-
nosis. Examples of drugs given in this
form are
antibiotic drugs
,
corticosteroid
drugs
,
antihistamine drugs
, and drugs
used to dilate or constrict the pupil.
eye, examination of
An inspection of
the structures of the
eyes
, either as part
of a
vision test
or to make a diagnosis
when an
eye disorder
is suspected.
An eye examination usually begins
with inspection of the external appear-
ance of the eyes, lids, and surrounding
skin. A check of eye movements is usu-
ally performed and the examiner looks
for
squint
. A check of the
visual acuity
in
each eye using a
Snellen chart
follows.
Refraction
testing (using lenses of dif-
ferent strengths) may be performed to
determine what glasses or contact lens-
es, if any, may be needed. A test of the
visual fields
may be performed, espe-
cially in suspected cases of
glaucoma
or
neurological conditions.
Colour vision
may be checked because loss of colour
perception is an indication of certain
disorders of the
retina
or
optic nerve
.
To
check for abrasions or ulcers, the
con-
junctiva
and
cornea
may be stained with
fluorescein
. Applanation
tonometry
is
an essential test for glaucoma.
The
ophthalmoscope
is an instrument
used to examine the inside of the eye,
particularly the retina. The slit-lamp
microscope, with its illumination and
lens magnification, allows examination
of the conjunctiva, cornea, front cham-
ber of the eye,
iris
, and
lens
. For a full
view of the lens and the structures
behind it, the
pupil
must be widely
dilated with
eye-drops
.
eye, foreign body in
Any material on
the surface of the
eye
or under the lid,
or an object that penetrates the eyeball.
A foreign body may cause irritation,
redness, increased tear production, and
blepharospasm
.
In some cases, a foreign
body left in the eye may cause a reac-
tion that results in permanent loss of
sight in both eyes.
Foreign bodies on or in the
conjuncti-
va
can usually be flushed out with
216
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