EYE, FOREIGN BODY IN
E
WHY IT IS DONE
Eye examinations are used to determine
the cause of visual disturbance or of
other symptoms relating to the eye.
They are also used to assess whether
corrective devices, such as glasses or
contact lenses, are necessary. Eye tests
are essential to discover certain serious
eye disorders,
such as
glaucoma
(in
w hich the fluid in the eye is at abnor-
mally
high
pressure),
because
such
disorders may be symptomless in the
early stages and only detectable during
an eye examination.
HOW IT IS DONE
An eye examination usually begins with
a physical inspection of the eyes, the
eyelids, and the surrounding skin. Eye
movements are usually checked and the
examiner looks for
squint
(misalign-
ment of the eyes).
Visual acuity
(sharpness of vision) in
each eye is investigated using a
Snellen
chart
,
the standard eye test wall chart.
Refraction
testing (using lenses of differ-
ent strengths) may then be performed
to determine precisely what glasses or
contact lenses, if any, are required.
An investigation of the
visual fields
(the extent of peripheral vision) may
also be carried out, especially in sus-
pected cases of glaucoma or a variety of
neurological conditions.
Colour vision
is
occasionally
checked
because loss of colour perception is a
sign of certain disorders of the
retina
(the light-sensitive inner layer at the
back of the eye) or of the
optic nerve
(w hich transmits impulses from the
retina to the brain). In order to check
for abrasions or ulcers, the
conjunctiva
(the transparent membrane covering
the white of the eye and inside of the
eyelids) and the
cornea
(the transparent
dome that forms the front of the eye-
ball) may be stained w ith
fluorescein
(an orange dye).
Applanation
tonometry
(measurement
of the pressure w ithin the eye) is an
essential test for glaucoma.
EQUIPMENT
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 for examination of the conjunc-
tiva, the cornea, the front chamber of
the eye, the
iris
(the coloured part of the
eye) and the
lens
(the component that
is responsible for focusing).
To obtain a full view of the lens and
the structures behind it, the
pupil
(the
circular opening in the centre of the
iris) must be widely dilated by using
special
eye-drops
.
CONDUCTING AN EYE EXAMINATION
In an eye examination, the ophthalmologist
checks the external appearance, eye
movement, visual acuity, visual field, and
colour vision. The eyes are checked for the
presence of a squint, abrasions, and ulcers.
Applanation tonometry and a refraction
test may also be carried out.
B l o o d
v e s s e l
O p t ic
d i s c
View of retina through ophthalmoscope
The retina (the inner back surface ofthe eye) is
examined to assess its health and to detect the
presence ofdisorders such as retinopathy.
Z
D
A
F
X
H
P T N D
X A Z F N
H T X U D F
U Z N D F X T
A P H T X Z N U
Applanation
tonometry
Measurement ofthe
pressure within the
eye is a test for
glaucoma.
Snellen chart
This chart is used
to checkthe visual
acuity of each eye;
the patient’s ability
to read letters of
different sizes from
the same distance
is assessed.
eye, foreign body in
Any material on the surface of the
eye
or under the eyelid, or an object that
penetrates the eyeball.
CAUSES
Particles of dust are the most common
type of foreign body to enter the eye.
Occasionally, a fragment of metal, plas-
tic, or wood may be deflected into the
eye. Rarely, an object travelling at high
speed may penetrate the eyeball.
SYMPTOMS AND COMPLICATIONS
A foreign body may cause irritation,
redness, increased tear production, and
blepharospasm
(uncontrollable
closure
and squeezing of the eyelid). Some for-
eign bodies left within the eyeball may
release damaging substances into the
eye, resulting in blindness. Other for-
eign bodies may remain intact but cause
infection that can lead to loss of sight.
Sympathetic
ophthalmitis
is a rare condi-
tion that may threaten sight even in the
uninjured eye.
TREATMENT
Foreign bodies on or in the
conjunctiva
(the
transparent membrane
covering
the white of the eye and lining the
inside of the eyelids) can usually be
flushed out with water. However, med-
ical attention is needed if the object has
penetrated the eyeball. The doctor may
drop
fluorescein
(an orange dye) into
the eye to reveal the presence of any
corneal abrasions
or sites of penetration.
Ultrasound scanning
or an
X-ray
of the eye
may also be performed.
Anaesthetic
eye-drops
may be applied
and a spatula used to remove an object
from the
cornea
(the transparent dome
that forms the front of the eyeball). The
eye may then be covered with a patch.
Antibiotic drugs
may be prescribed to
fight infection.
eye injuries
Eye
injuries may be caused by a blow to
the eye or penetration of a foreign body
(see
eye, foreign body in
) .
However, the
eye often escapes serious injury because
it is protected by the surrounding bone
and the rapid blink reflex.
A blow to the eye may cause tearing
of the
iris
(the coloured part of the eye)
or the
sclera
(the white of the eye), with
collapse of the eyeball and potential
blindness. M inor injuries may lead to
a
vitreous haemorrhage
(bleeding into
the gel-filled cavity behind the lens);
hyphaema
(bleeding
into
the
front
chamber of the eye);
retinal detachment
;
or injury to the trabeculum (the chan-
292
previous page 291 BMA A Z Family Medical Encyclopedia   2004 read online next page 293 BMA A Z Family Medical Encyclopedia   2004 read online Home Toggle text on/off