7/27/2019 Fluorescein Angiography 1

http://slidepdf.com/reader/full/fluorescein-angiography-1 1/2

Fluorescein angiography allows visualization of blood flow in retinal and choroidal tissues, permitting diagnostic

support in many ocular diseases. In particular, fluorescein angiography has become a very important tool in the

diagnosis and treatment of chorio-retinal diseases. However, limitations of fluorescein angiography in imaging

the choroidal circulation and associated pathologies prompted the use of alternative dyes to improve choroidal

angiography.

Indocyanine green angiography is a diagnostic study where indocyanine green, a fluorescent dye, is injected

intravenously, and observations of the retina are made at intervals as increasing intensity of retinal and

choroidal circulation is displayed. Indocyanine green angiography is used for the imaging of retinal and

choroidal vasculatures. It is effective when used as an adjunct to fluorescein angiography in the diagnosis and

treatment of ill-defined choroidal neovascularization (i.e., associated with age-related macular degeneration). It

is generally used in evaluating retinal neovascularization, serous detachment of retinal pigment epithelium,

hemorrhagic detachment of retinal pigment epithelium, and retinal hemorrhage.

Indocyanine green angiography has been under development for the past 30 years as an imaging method for 

the choroidal vasculature. Although standard fluorescein angiography is widely used to evaluate exudative

and proliferative lesions of the retina, its diagnostic ability in imaging the choroid is limited because of dye

scatter by the overlying pigmented structures of the fundus, and also due to leakage of fluorescein through the

fenestrated capillaries of the choroid. Improvements in indocyanine green angiography, specifically the

development of high resolution digital imaging systems, have permitted the technical feasibility and

commercialization of the technology.

The most commonly proposed application of indocyanine green angiography is the detection of choroidal

neovascularization, a common component of age related macular degeneration.

7/27/2019 Fluorescein Angiography 1

http://slidepdf.com/reader/full/fluorescein-angiography-1 2/2

Angiography is a diagnostic test used by ophthalmologists to photograph structures in the back of the eyeand is especially useful in finding damage to the blood vessels, which nourish the retina. There are two

types of angiography: fluorescein and indocyanine green (ICG). Fluorescein angiography is used primarily

to study blood circulation in and just beneath the surface of the retina, while ICG angiography is better forphotographing the deeper choroidal vessels (See Anatomy of the Eye).

The purpose of either type of angiography is to determine whether there are irregularities in thecirculatory system of the retina. Several serious eye disorders, such as diabetic retinopathy, affect retinal

circulation and are usually studied with the fluorescein procedure. Other problems, such as age-related

macular degeneration, are caused by leakage from the deeper choroidal blood vessels. In these cases, theICG procedure can provide additional information, which may not be available through a fluoresceinangiography.

In both angiography procedures, a small amount of colored dye is injected into a vein in the arm where it

travels through the circulatory system and into the vessels in the eye. The dye makes these vessels visible

to a special camera that is used to take photographs used by the doctor to diagnose various disorders of the eye.

How is fluorescein angiography performed? In fluorescein angiography, a small amount of vegetable-

based dye (sodium fluorescein which is either orange or yellow in color) is injected into an arm vein. The

dye travels through the circulatory system and, in about 15 seconds, reaches the blood vessels in the

retina and the choroid, the major blood vessel of the eye lying between the retina and the sclera. 

During a period of 2 to 5 seconds, the dye travels through the capillaries and fills the veins. Rapid,sequential black and white photographs, taken as the dye circulates, document how the dye enters the

different blood vessels. Diseases of the retina, choroid, and retinal blood vessels will interrupt the

progression of dye. Depending on the specific problem, another set of photographs may be taken about 15minutes later in order to show staining that can possibly indicate leakage or swelling on the retina. Thesephotographs will detect any abnormalities in the retina that are not visible by other procedures.

Fluorescein angiography takes about 20 to 30 minutes and is virtually painless. After the test is complete,

the pupils may remain dilated for several hours, so it is a good idea to arrange for another person toprovide your transportation home.

What is involved in a indocyanine green angiography test? As in fluorescein angiography, ICG

angiography requires the injection of dye into a vein in the arm. The dye travels through the circulatory

system and reaches the blood vessels in the retina and the choroid. The difference between fluoresceinand ICG angiography is primarily in the type of dye that is used. The green ICG dye glows or "fluoresces"

and, unlike the dye used in the fluorescein procedure, allows the camera to see through blood, fluid, andpigments that obscure certain conditions from view. The fluorescing quality of the ICG dye also allowsspecial digital cameras to capture and view images as the test is being done. 

ICG is especially helpful in situations where the source of leakage may be obscured by a hemorrhage of the retina, which makes interpretation of fluorescein studies difficult. To date, the most useful application

of the ICG procedure is the diagnosis and treatment of age-related macular degeneration, the leading

cause of new blindness in people over the age of 55 in this country. Precise application of a laser is critical

to the treatment of the more serious (wet) form of this disease. The ICG angiography often enables theophthalmologist to do a better job of pinpointing the location of the leakage.

Side effects from either angiography procedure are minimal. The dye used in fluorescein angiography

sometimes causes temporary, harmless discoloration of the skin and urine, and a small percentage of 

patients may feel slightly nauseated for a short time during the initial phase of the procedure. Allergicreactions to the ICG dye are rare. However, patients allergic to iodine or shellfish, or those with a historyof liver disease, should advise their physician.