Fluorescein angiography (FA), fluorescent angiography (FAG), or fundus fluorescein angiography (FFA) is a technique for examining the circulation of the

retina The retina (; or retinas) is the innermost, photosensitivity, light-sensitive layer of tissue (biology), tissue of the eye of most vertebrates and some Mollusca, molluscs. The optics of the eye create a focus (optics), focused two-dimensional ...

and choroid (parts of the fundus) using a fluorescent dye and a specialized camera. Sodium fluorescein is added into the systemic circulation, the retina is illuminated with blue-green light at a

wavelength In physics and mathematics, wavelength or spatial period of a wave or periodic function is the distance over which the wave's shape repeats. In other words, it is the distance between consecutive corresponding points of the same ''phase (waves ...

of 490 nanometers, and an angiogram is obtained by photographing the fluorescent green light that is emitted by the dye. The fluorescein is administered intravenously in intravenous fluorescein angiography (IVFA) and orally in oral fluorescein angiography (OFA). The test is a dye tracing method. The fluorescein dye also reappears in the patient urine, causing the urine to appear darker, and sometimes orange. It can also cause discolouration of the saliva. Fluorescein angiography is one of several

health care Health care, or healthcare, is the improvement or maintenance of health via the preventive healthcare, prevention, diagnosis, therapy, treatment, wikt:amelioration, amelioration or cure of disease, illness, injury, and other disability, physic ...

applications of this dye, all of which have a risk of severe

adverse effect An adverse effect is an undesired harmful effect resulting from a medication or other intervention, such as surgery. An adverse effect may be termed a "side effect", when judged to be secondary to a main or therapeutic effect. The term compli ...

s. See fluorescein safety in health care applications. Fluorescein angiography does not involve the use of

ionizing radiation Ionizing (ionising) radiation, including Radioactive decay, nuclear radiation, consists of subatomic particles or electromagnetic waves that have enough energy per individual photon or particle to ionization, ionize atoms or molecules by detaching ...

. Fluorescein angiography was pioneered by German

ophthalmologist Ophthalmology (, ) is the branch of medicine that deals with the diagnosis, treatment, and surgery of eye diseases and disorders. An ophthalmologist is a physician who undergoes subspecialty training in medical and surgical eye care. Following a ...

Achim Wessing, who published his findings in 1969.

Equipment

* Exciter filter: Allows only blue light to illuminate the retina. Depending on the specific filter, the excitation wavelength hitting the retina will be between 465 and 490 nm. Most only allow light through at a wavelength of 490 nm. * Barrier filter: Allows only yellow-green light (from the fluorescence) to reach the camera. Both filters are interference bandpass filters, which means they block out all light except that at a specific wavelength. The barrier filter only allows light with a wavelength of 525 nm, but depending on the filter it can be anywhere from 520 to 530 nm. * Fundus camera, either digital or with camera body containing black and white, or slide positive film.

Technique

* Baseline color and black and white red-free filtered images are taken prior to injection. The black and white images are filtered red-free (a green filter) to increase contrast and often gives a better image of the fundus than the color image. * A 6-second bolus injection of 2-5 cc of sodium fluorescein into a vein in the retina * Local injection * A series of black-and-white or digital photographs are taken of the retina before and after the fluorescein reaches the retinal circulation (approximately 10 seconds after injection). The early images allow for the recognition of autofluorescence of the retinal tissues. Photos are taken approximately once every second for about 20 seconds, then less often. A delayed image is obtained at 5 and 10 minutes. Some doctors like to see a 15-minute image as well. * A filter is placed in the camera so only the fluorescent, yellow-green light (530 nm) is recorded. The camera may however pick up signals from pseudofluorescence or autofluorescence. In pseudofluorescence, non-fluorescent light is imaged. This occurs when blue light reflected from the retina passes through the filter. This is generally a problem with older filters, and annual replacement of these filters is recommended. In autofluorescence, fluorescence from the eye occurs without injection of the dye. This may be seen wit
optic nerve head drusen
or calcific scarring. * Black-and-white photos give better contrast than color photos, which aren't necessary because the filter transmits only one color of light.

Normal circulatory filling

''times are approximate'' * 0 seconds – injection of fluorescein * 9.5 sec – posterior ciliary arteries * 10 sec – choroidal flush (or "pre-arterial phase") * 10–12 sec – retinal arterial stage * 13 sec –

capillary A capillary is a small blood vessel, from 5 to 10 micrometres in diameter, and is part of the microcirculation system. Capillaries are microvessels and the smallest blood vessels in the body. They are composed of only the tunica intima (the inn ...

transition stage * 14–15 sec – early venous stage (or "laminar stage", "arterial-venous stage") * 16–17 sec – venous stage * 18–20 sec – late venous stage * 5 minutes – late staining Fluorescein enters the ocular circulation from the

internal carotid artery The internal carotid artery is an artery in the neck which supplies the anterior cerebral artery, anterior and middle cerebral artery, middle cerebral circulation. In human anatomy, the internal and external carotid artery, external carotid ari ...

via the ophthalmic artery. The ophthalmic artery supplies the choroid via the short posterior ciliary arteries and the retina via the central retinal artery, but the route to the choroid is typically less circuitous than the route to the retina. This accounts for the short delay between the "choroidal flush" and retinal filling.

Pathologic findings

Pathologic changes are recognized by the detection of either hyperfluorescence or hypofluorescence. Causes of hyperfluorescence: :window/transmission (filling) defects :leaking defects (i.e. capillary leakage, aneurysm, neovascularization) :pooling defects :staining :abnormal vasculature Causes of hypofluorescence: :blocking defect (i.e. blood) :filling defect (capillary nonperfusion/blockage) Fluorescein angiography is used by physicians specializing in the treatment of eye diseases ( ophthalmologists) to evaluate the vasculature of the

, 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.

References

Additional references