As part of their retinal evaluation, many patients will undergo fundus photographs and fluorescein angiography. Fundus photographs are color photographs of the retina in which a high-magnification camera is used to photograph the back of the eye, its blood vessels and tissues. These photographs allow the doctor to study the back of the eye and – for patients with a chronic eye problem – document the eye for future reference.
A fluorescein angiogram combines a fluorescent dye with rapid-sequence photography to study the blood flow, vessels and tissues of the retina. After the fluorescein dye is injected into an arm vein, 30 to 60 photos are taken as the dye passes through the blood vessels of the retina, allowing the doctor to identify problem areas of the retina or retinal blood vessels. The entire test takes about 45 minutes.
Fluorescein is a relatively safe dye. As with any injected medicine, there is a small risk of an allergic reaction. A few patients may experience nausea. However, unlike the dye used for CT scans, heart angiograms and kidney studies, fluorescein dye contains no iodine. Therefore, the risk of allergic reactions or kidney problems from the injection is much lower. Patients who have allergies to iodine dyes can safely receive the fluorescein injection.
After the test, vision may be blurry for several hours due to the multiple bright flashes of light. The dye also gives the skin an orange-brown tinge for several hours after treatment. The dye is eventually passed in the urine, which may appear bright green for the next 24 hours.
Fluorescein angiography uses photography not X-rays, which means there is no exposure to radiation from this test. Because angiograms are so effective at detecting abnormal blood vessels, patients often undergo repeat angiograms on return visits to evaluate the response to treatment and determine the need for additional treatments.
Occasionally, patients undergo a different type of angiography called Indocyanine Green Angiography (ICG). This test is similar to a fluorescein angiogram except that it uses indocyanine green dye. In some cases, ICG may allow identification of an area of leakage not visible on the fluorescein angiogram.