EYE, EXAMINATION OF
moved by six delicate muscles. The eye
has a tough, white outer layer known as
At the front of the sclera,
(a transparent, thin-walled
dome) serves as the main “lens” of the
eye and does most of the focusing.
Behind the cornea is a shallow cham-
ber filled with watery fluid (called the
aqueous hum our), at the back of w hich
(the coloured part of the eye)
(circular opening), w hich
appears black. Tiny muscles alter the
size of the pupil in response to changes
in light intensity in order to control the
amount of light entering the eye.
Behind the iris, and in contact with
it, is the crystalline lens, w hich is sus-
pended by fibres from a circular ring of
the ciliary body changes the shape of
the lens, enabling fine focusing.
The main cavity of the eye contains a
clear gel (the vitreous humour) and is
located directly behind the lens. On the
inside of the back of the eye is the retina,
a complex structure of nerve tissue that
is extremely sensitive to light. The retina
requires a constant supply of oxygen
and glucose. To meet this need, a thin
network of blood vessels, the choroid
plexus, lies immediately under it. The
is continuous at the front with
the ciliary body and the iris; these three
parts constitute the uveal tract.
CONJUNCTIVA AND EYELID
The eyeball is sealed off by a trans-
parent, flexible membrane called the
w hich is attached to the skin
at the corners of the eye and forms the
inner lining of the eyelids. The conjunc-
tiva contains mucus-secreting glands.
These, together with the meibomian
glands in the eyelids (which secrete an
oily fluid), provide the tear film that
protects the cornea and conjunctiva.
Blinking, a protective
spread the tear film evenly over the
cornea to enable clear vision.
used to replace an
that has been surgically removed. An
artificial eye is worn purely for cosmetic
and psychological reasons and fits neat-
ly behind the eyelids into the cavity
removed. Some movement of the artifi-
cial eye may be achieved by attaching
the muscles that normally move the eye
to the remaining conjunctival mem-
or to a plastic
implant placed in the eye socket.
Often called “ glass eyes", artificial
eyes were once made of glass; now an
easily mouldable plastic material is used.
Medication in solution that is used in
the treatment of eye disorders or to aid
in their diagnosis. Examples of drugs
given in this form are
drugs used either to
dilate (widen) or constrict (narrow) the
pupil, the circular opening in the centre
of the iris, and
A specified number of eye-drops are
applied to the inside of the lower eyelid
after the lid has been drawn down
using the tip of a clean finger. Blinking
helps to spread the medicated solution
evenly around the eyeball.
eye, examination of
An inspection of the structures of the
either as part of a
make a diagnosis when an eye disor-
der is suspected.
disorders are minor, but some
can cause loss of vision unless treated.
disorders of the cornea
disordersof the retina
(misalignment of the eyes) may
be congenital (present at birth). Other
examples of congenital defects are
(uncontrollable, jerky eye
pigment in the iris), and developmental
defects affecting the cornea and retina.
A rare birth defect is
(abnormally small size of one or both
(opacity of the lens) can
sometimes be seen in newborn infants.
(inflammation of the
conjunctiva) is the most common eye
(a persistent disease
of the cornea or conjunctiva) or severe
bacterial conjunctivitis can impair
vision. Corneal infections can lead to
blurred vision or corneal
not treated early. Endophthalmitis
(infection within the eye) can occur as
a result of injury to the eye or infection
elsewhere in the body.
Impaired blood supply
Narrowing, blockage, or
retinal blood vessels may cause visual loss.
most common cancerous tumour of the
(a cancer of the retina)
most commonly affects children.
affects the eyelid and may result
from excessive exposure to sunlight.
deficiencies affect the eyes.
Vitamin A deficiency may lead to
(corneal and conjunctival
(corneal softening and
(inflammation of the iris, choroid,
and/or ciliary body) may be caused by
infection or an
which the body’s immune system attacks
its own tissues), such as
of the retina is
common in elderly people, as is cataract.
is a pro-
gressive, age-related loss of the ability
to focus at close range.
vision in one eye unrelated to structural
abnormality) is often due to squint.
(increased pressure within the
eyeball), can lead to permanent visual
the retina lifts
away from the eye’s underlying layer.
used to view the eye.Vision is evaluated