Fluorescein angiography (FA), is a technique for examining the circulation of the retina and choroid (parts of the fundus) using a fluorescentdye and a specialized angiographic camera. It involves administration of sodium fluorescein
 into the systemic circulation, and then an angiogram is obtained by photographing the fluorescence emitted after illumination of the retina with blue light at a wavelength of 490 nanometers.
Pathologic changes are recognized by the detection of either hyperfluorescence or hypofluorescence.
Fluorescein angiography is used by physicians specializing in the treatment of eye diseases (ophthalmologists) to evaluate the vasculature of the retina, choroid, optic disc, and iris.
 Among the common groups of ophthalmologic disease, fluorescein angiography can detect diabetic retinopathy (neovascularization), vein occlusions, retinal artery occlusions,
 edema of the optic disc, and tumors. Additionally, the transit time (the period between injection of the dye and when it appears in the examined blood vessels) can provide an objective measurement of the rate of blood flow through the imaged blood vessels