What is Fluorescein Angiography?
Fluorescein angiography is a diagnostic test in which the retina, the light sensitive tissue in the back of the eye is photographed.
A water soluble dye (fluorescein) is injected into a vein in the arm. The dye travels through the veins and arteries (blood vessels) of the retina, the camera takes multiple photographs to record its passage. If the blood vessels are abnormal, the dye may leak into the retina. Damage to the membrane underneath the retina or the appearance of abnormal new blood vessels growing beneath the retina may also be revealed.
The precise location of abnormalities may be determined by a careful interpretation of the fluorescein angiogram.
When is it done?
If we suspect abnormalities of the retina we may recommend fluorescein angiography. It is also done to follow the course of disease and monitor treatment results.
Diabetes, the main cause of blindness in patientsunder the age of 55, may cause the blood vessels of the retina to leak fluid or bleed. These abnormalities can be treated with a laser to help prevent loss of vision.
Age related macular degeneration is the leading cause of blindness in patients over the age of 55. In some cases, small blood vessels can be seen under the retina which can be treated with a laser in an attempt to prevent severe visual loss. Knowing exactly where a leak is, for example, can guide laser treatment with pinpoint accuracy.
After the fluorescein dye is injected, your skin will turn yellow for several hours. This colour disappears as the dye is filtered out of the body by the kidneys. Your urine may be orange for up to 24 hours after the test. Some patients experience nausea for a few seconds. If the dye leaks out of a fragile vein during the injection, localised burning and yellow staining of the skin may occur. This burning usually lasts only a short time and the staining will go away in a few days.
Severe allergic reactions to fluorescein dye are rare. Skin rash and itching are treated with oral or injectable antihistamines. Very severe reactions where the blood pressure falls drastically are very, very rare. Because we use a digital camera the dose of fluorescein is only half that normally used, so adverse effects are minimised.