RETINAL ARTERY OCCLUSION
RETINOSCOPY
retinal artery occlusion Blockage of
an artery supplying blood to the
retina,
most commonly due to
thrombosis
or
embolism,
The disorder can result in
permanent blindness or loss of part of
the field of vision, depending on the art-
ery affected and whether or not the
condition can be treated quickly enough.
retinal detachment Separation of the
retina
from the outer layers at the back
of the eye. Detachment may follow an
eye injury but usually occurs spontane-
ously. It is usually preceded by a
retinal
tear
, and is more common in highly
myopic (shortsighted) people and in
people who have had
cataract surgery.
The detachment is painless. The first
symptom is either bright flashes of light
at the edge of the field of vision, accom-
panied by
floaters,
or a black “drape”
obscuring vision.
Urgent treatment is required and usu-
ally involves surgical repair of the
underlying tear. If the macula (site of
central vision) has not been detached,
the results can be excellent.
retinal haemorrhage Bleeding into the
retina
from
1
or more blood vessels, due
to
diabetes mellitus, hypertension,
or
reti-
nal vein occlusion.
When the macula
(site of central vision) is involved, vision
is severely impaired. Peripheral haemor-
rhages may be detected only when the
eye is examined with an
ophthalmoscope
.
retinal tear The development of a split
in the retina, usually caused by degen-
eration. A tear is more common in
people with severe
myopia.
A retinal
tear may also be caused by a severe eye
injury.
Retinal detachment
usually fol-
lows a retinal tear. If a retinal tear is
found before there is any detachment,
the hole is sealed by
laser treatment
or
cryopexy (application of extreme cold).
retinal vein occlusion Blockage of a
vein carrying blood away from the retina.
It usually results from
thrombosis
in the
affected vein, and is more common in
people who have
glaucoma
. Retinal vein
occlusion
may cause visual
distur-
bances, glaucoma, or blindness.
retinitis Inflammation affecting the
ret-
ina.
(See also
retinopathy.)
retinitis pigmentosa An inherited con-
dition in which there is degeneration of
the rods and cones of the
retina
at the
back of both eyes.
The 1st symptoms appear during or
after adolescence and include night
blindness. Tests show a ring-shaped area
of blindness which, over some years,
extends to destroy an increasing area of
the
visual field
, though central vision is
retained, often for many years. Opthal-
moscopy reveals several masses of black
pigment corresponding to the areas of
visual loss. Affected individuals and their
parents should have
genetic counselling
.
retinoblastoma A cancer of the
retina
that affects infants. The first indications
of this disorder may be a
squint
caused
by blindness in the affected eye or a vis-
ible whiteness in the pupil. Without
early treatment,
retinoblastoma can
spread to the orbit (eye socket) and
along the
optic nerve
to the brain.
Retinoblastoma has a genetic basis.
People with this cancer lack part of one
of the
chromosomes
in pair number 13.
Newborn infants from affected families
are given regular eye examinations, and
prospective parents in affected families
should have
genetic counselling
.
Treatment is by removing the eye, or
by
radiotherapy
. If both eyes are involved,
the one worse affected may be removed
and the other given radiotherapy.
retinoids See
vitamin A.
retinol The principal form of
vitamin A
found in the body.
retinopathy Disease of the
retina
, usu-
ally caused by
diabetes mellitus
or
persistent
hypertension
.
In diabetic retinopathy, the capillaries
in the retina are affected by
aneurysms
,
leak fluid, and bleed into the retina.
Abnormal capillaries then grow on the
retinal surface. As these are fragile,
vit-
reous haemorrhage
may occur. Fibrous
tissue may also grow into the
vitreous
humour
. Treatment by laser surgery can
often halt the progress of the condition.
In hypertensive retinopathy the retinal
arteries become narrowed. Areas of ret-
ina may be destroyed, and bleeding and
white deposits may occur in the retina.
(See also
retrolental fibroplasia.)
retinoscopy A type of
vision test
in which
a beam of light is shone from an instru-
ment called a retinoscope into each eye
R
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