This technique is used to study the blood vessels in the light-sensitive retina of the eye. A fluorescent dye (fluorescein) is injected into the circulatory system through one of the veins in the arm. As the dye passes through the retinal vessels, a series of photographs (fluorescein angiograms) is taken to define any underlying abnormalities. The ophthalmologist can then assess the extent of the damage. The test is painless, but your skin and urine may turn dark yellow until all the dye has been excreted.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.