There are two main types of retinal angiography. The most
common and most useful is Fluorescein angiography. Indocyanine
Green angiography is used in special circumstances or when
the patient is allergic to fluorescein.
Fluorescein Angiography
 Fluorescein
angiography, a clinical test to look at blood circulation
inside the back of the eye, aids in the diagnosis of retinal
conditions associated with diabetes, age-related macular degeneration,
and other eye abnormalities. The test can also help follow
the course of a disease and monitor its treatment. It may
be repeated on multiple occasions with no harm to the eye
or body.
Fluorescein, a harmless orange-red dye, is injected into a
vein in the arm. The dye travels through the body to the blood
vessels in the retina, the light-sensitive nerve layer at
the back of the eye. A special camera with a green filter
flashes a blue light into the eye and takes multiple photographs
of the retina. The technique uses regular photographic film.
No X-rays are involved.
If there are abnormal blood vessels, the dye leaks into the
retina or stains the blood vessels. Damage to the lining of
the retina or atypical new blood vessels may be revealed as
well. These abnormalities are determined through a careful
interpretation of the photographs by an ophthalmologist.
The dye can discolor skin and urine until it is removed
from the body by the kidneys. There is little risk in having
fluorescein angiography, though some people may have mild
allergic reactions to the dye. Severe allergic reactions
have been reported but very rarely. Being allergic to X-ray
dyes with iodine does not mean you'll be allergic to fluorescein.
Occasionally, some of the dye leaks out of the vein at the
injection site, causing a slight burning sensation that
usually goes away quickly.
Indocyanine Green Angiography (ICG)
ICG angiography is a clinical test used to detect abnormal
blood vessels in the choroid, the layer of blood vessels
under the retina. These abnormal blood vessels, typically
associated with macular degeneration, may cause bleeding,
scarring, and vision loss. If the blood vessels can be restricted
by laser surgery, vision loss may be stabilized or improved.
Indocyanine, a harmless green dye, gives off infrared light.
When injected into the bloodstream, the dye travels through
the veins to the blood vessels in the eye. A video camera
connected to a computer picks up the infrared light and
makes a picture of the blood's circulation. No film or x-rays
are involved.
Following the test, the liver removes the dye. There is
little risk in having an ICG angiogram. Some people may
have mild allergic reactions and, although rare, a few severe
allergic reactions have been reported in people allergic
to iodine, X-ray dyes and shellfish.
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