Ophthalmic Fluorescein and Indocyanine Green Angiography
Edgbaston Eye Consultants is proud to be able to offer combination fluorescein and indocyanine green angiography. These are advanced diagnostic techniques not available in any other private clinic and form part of the mission of Edgbaston Eye Consultants to offer the best eye treatments that are designed around your lifestyle.
What is eye angiography?
Fluorescein and indocyanine green angiography are diagnostic tests which use special cameras to photograph the structures in the back of the eye. These tests are very useful for finding leakage or damage to the blood vessels which nourish the retina (light sensitive tissue). In both tests, a coloured dye is injected into a vein in the arm of the patient. The dye travels up the arm and through the blood circulation to reach the vessels in the eye called the retina and a deeper tissue layer called choroid (see Fig. 1 below). Neither test involves the use of X-rays or harmful forms of radiation.
Fluorescein is a yellow dye which glows in visible light. Indocyanine is a green dye which fluoresces with invisible infrared light; it requires a special digital camera sensitive to these light rays. Indocyanine green angiography has only recently become a practical technique as these cameras have just become available.
Figure 1. Schematic drawing illustrating a cross-section of the back of the eye with indocyanine green dye in the both the retinal blood vessels and the deeper choroidal vessels. The retinal pigment epithelium (pigmented layer) lies between the retina and the choroidal vessels. The dye highlights the vessel as seen in the angiogram insert (upper left).
Why is eye angiography performed?
Both tests can help retina specialists diagnose and evaluate specific eye diseases. Fluorescein dye is best for studying the retinal circulation (see Fig. 2a below) while indocyanine green is often better for studying the deeper choroidal blood vessel layer (see Fig. 2b below). Certain eye disorders, such as diabetic retinopathy and retinal vascular occlusive disease affect primarily the retinal circulation and are usually imaged with fluorescein dye. In other disorders, such as age-related macular degeneration, where leakage is from the deeper choroidal vessels, both tests may be useful. Indocyanine green angiography is especially helpful when there is leakage of blood which may make interpretation of fluorescein studies difficult.
Figure 2a. This fluorescein study shows fluid leakage in a patient with the "wet" form of age-related macular degeneration. The retinal blood vessels are easily seen.
Figure 2b. This indocyanine green angiogram of the same patient shows the deeper choroidal vessels. The leaky vessels (choroidal neovascularization) are shown well here.
When abnormal vessels or leakage is identified with an angiogram, treatment with drugs into the eye or laser treatment may be indicated to prevent vision loss. The tests can also be useful for following the course of disease or response to treatment.
What are the risks of eye angiography?
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.
Reactions to the dye
Iodine. While fluorescein contains no iodine and is safe in patients known to be allergic to iodine, indocyanine green is currently formulated with iodine and should not be used in these individuals. Iodine is contained in seafood, especially shelled seafood and crustaceans (shrimps). Please tell the nurse or the doctor if you had a bad reaction following a seafood meal. Stomach upset or food poisoning with diarrhoea are not part of a sea food allergic reaction.
Mild itching and a skin rash is common after the dye test and 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 immediate medical treatment.
Some people may experience slight nausea after dye injection that usually passes quickly.
There is a possibility of an infiltrate of the dye into the skin at the injection site; this would cause some discomfort or discolouring of the skin for several days. Very rarely severe pain followed by serious local skin damage (necrosis) can occur following inadvertent extravasation of dye at the injection site.
What you will notice after angiography.
Fluorescein dye will turn a patient's urine orange and may slightly discolour the skin as well for a brief period. If you drink more water than usual you will accelerate the natural clearance of the dye through your kidneys and return more quickly to your normal skin and urine colour.