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Photography
of the Retina with Dye
Fluorescein Angiography and Indocyanin Green Angiography
What
is fundus angiography?
Fluorescein and indocyanine green angiography are tests
that use special cameras to photograph the structures in the
back of the eye. These tests are very useful for locating
the damage to the blood vessels that nourish the retina (light
sensitive tissue) and, in turn, checking on the health of
the retina itself. In both tests, a colored dye is injected
into a vein in the arm of the patient. The dye travels through
the circulatory system and reaches the vessels in the retina
and those of a deeper tissue layer called the choroids. Neither
of the tests uses any harmful forms of radiation.
Fluorescein is a yellow dye, which glows in visible light.
Indocyanine is a green dye that fluoresces with invisible
infrared light; it requires a special digital camera sensitive
to these light rays This indocyanine green angiography helps
your doctor make the correct diagnosis and plan the best course
of treatment especially in diseases like age related macular
degeneration (AMD).
How is fundus
angiography done?
Before the procedure, you will be asked questions about
your general health and the medications that you are using.
A self-explanatory consent form, which explains the side effects
in detail, will be provided to you. You will have to give
your consent before the procedure. You should have a light
meal before undergoing the procedure and be accompanied by
a family member or friend.
Eye drops will be put in your eyes to enlarge the pupils —
this takes approximately 30 minutes. You will then be asked
to sit still in front of the camera while a series of colour
photographs of your eyes are taken. You will be given an injection
in your arm, and more photographs will be taken.
The test takes approximately 15-30 minutes.
What are the side
effects?
Both fluorescein angiography and indocyanine green
angiography are considered very safe and serious side effects
from these tests are uncommon. However, there is the possibility
that a patient may have a reaction to the dyes. While fluorescein
contains no iodine and is safe in patients known to be allergic,
indocyanine green is currently formulated with iodine and
should not be used in individuals with any known allergies.
Some people may experience slight nausea after the dye injection,
but the feeling usually passes quickly.
Patients who are allergic to
the dye can develop itching and a skin rash. These symptoms
generally respond quickly to oral medications such as anti-histamines
or steroids. Very rarely, a sudden life-threatening allergic
reaction called anaphylaxis can occur. This condition requires
medical treatment.
There is also the possibility
of an infiltrate of the dye into the skin at the injection
site; this may cause some discomfort or discoloring of the
skin for several days. The fluorescein dye will turn a patient's
urine orange and may slightly discolor the skin as well for
a brief period. Your physician can explain the individual
risks of these procedures, for certain patients, including
pregnant women
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