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Fluorescein angiography was first successfully used in the human eye in 1961* and has evolved since then as one of the fundamental imaging techniques in the eye. It is a test that helps in the differentiation of retinal disease and is used to determine if laser treatment of the retina is warranted.
A contrast medium called Sodium Fluorescein is injected into a vein in the arm. The dye travels quickly through the body's circulatory system, and is photographed in black and white as it travels through the eye. The same camera used for fundus photography is employed for this procedure. Two special filters are used to limit the image to the color of light being emitted from the fluorescent dye.
About twelve seconds after the injection, the dye appears in the arteries of the retina. Over a two to five second period, the dye travels through the very small vessels, or capillaries, and fills the veins. Ten minutes after the injection, the dye has mostly evacuated from the eye, having stained the optic nerve head.
Figure 1: Normal Fluorescein Angiogram. Arterial phase illustrating sodium fluorescein dye in the retinal arteries before filling the retinal veins.
Figure 2: Normal Fluorescein Angiogram. Early venous phase illustrating sodium fluorescein dye beginning to fill the retinal veins.
Figure 3: Normal Fluorescein Angiogram. Complete fill of retinal arteries and veins with sodium fluorescein dye.
Figure 4: Normal Fluorescein Angiogram. The late phase of the angiogram demonstrates fading of the sodium fluorescein dye in the retinal vessels.
This normal progression of dye is interrupted by many diseases of the choroid, retina, and retinal vasculature. A fluorescein angiogram of a patient with ocular complications due to diabetes (diabetic retinopathy) reveals vascular irregularities when compared with the normal angiogram.