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, 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.