What is Fluorescein Angiography (FA)?
Fluorescein angiography is an eye test that uses a fluorescent dye and a camera to look at blood flow in the retina and choroid, the two layers in the back of the eye. This test is very useful in the management of diabetic retinopathy and macular degeneration. The test is done to help the doctor confirm a diagnosis, to provide guidelines for treatment, and to keep a permanent record of the vessels at the back of the eye.
How is the Procedure Done?
The pupils will be dilated with eye drops and the yellow dye is injected into a vein of the arm. During the injection, some experience a warm feeling or a hot flush sensation, however this only lasts seconds and then disappears. Following the injection, photos are taken quickly over a period of about 60 seconds as the dye enters the vessels at the back of your eye. It is common for the skin to have a yellow tinge after the procedure due to the fluorescent dye and this may take two days to wear off.
Are There Possible Adverse Reactions?
Fluorescein angiography is an invasive procedure. Adverse reactions occur in 5 to 10 percent of patients and can range from mild to severe. Nausea and occasional vomiting are the most common reactions and require no treatment. More severe reactions are rare, but include hives, laryngeal edema (swelling of the larynx), bronchospasm (difficulty breathing), syncope (passing out), anaphylaxis (allergic reaction that requires a shot of medicine to counteract it), myocardial infarction and cardiac arrest (heart attack and heart stoppage). Although there are no known risks or adverse reactions associated with pregnancy, most practitioners will avoid performing fluorescein angiography in pregnant women, especially in their first trimester. Although life-threatening reactions during angiography are rare, the angiographic facility should be properly equipped and prepared to manage serious reactions to the procedure. It is generally recommended that a physician be present or available during angiography.
Why is this Test Done?
In macular degeneration, angiography is useful in identifying the presence and location of subretinal neovascularization (new blood vessels growing under the retinal which will leak and bleed). Post-treatment angiograms also check how effective the laser treatment was. Some retinal conditions exhibit a characteristic patterns of fluorescein staining which can confirm the diagnosis. Stargardt's Disease is an example, showing an absence of choroidal fluorescence and a central bulls-eye staining pattern in the macula. With photodynamic therapy (PDT), pre-treatment angiograms are used to determine the location and size of the areas to be treated. The actual size of the area can be measured and the appropriate spot size of the PDT laser can be calculated.
What is Indocyanine Green?
ICG (indocyanine green) is a green dye that fluoresces with invisible infrared light. Fluorescein angiography is most useful for studying the retinal circulation, whereas ICG is better suited for studying the deeper choroidal circulation. Fluorescein angiography is most frequently used for evaluation of patients with diabetic retinopathy, occlusive diseases such as retinal vein and arterial occlusions, and evaluation for wet macular degeneration. ICG angiography is most frequently used when blood is present in the macula of patients with the wet form of macular degeneration because this may make interpretation of fluorescein angiography more difficult.
