retinal artery occlusionBlockage of
an artery supplying blood to the retina,
most commonly due to thrombosisor
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 detachmentSeparation of the
retinafrom 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 byfloaters, 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 haemorrhageBleeding into the
retinafrom 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 tearThe 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 treatmentor
cryopexy (application of extreme cold).
retinal vein occlusionBlockage 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.
retinitisInflammation affecting the ret-
ina. (See also retinopathy.)
retinitis pigmentosaAn inherited con-
dition in which there is degeneration of
the rods and cones of the retinaat 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 individualsand their
parents should have genetic counselling.
retinoblastomaA cancer of the retina
that affects infants. The first indications
of this disorder may be a squintcaused
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 chromosomesin 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.
retinoidsSee vitamin A.
retinolThe principal form of vitamin A
found in the body.
retinopathyDisease 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 haemorrhagemay 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.)
retinoscopyA type of vision testin which
a beam of light is shone from an instru-
ment called a retinoscope into each eyeRETINAL ARTERY OCCLUSION RETINOSCOPY
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