Fluorescein angiography

Fluorescein angiography
Fluorescein angiography
	Retina during the effects of fluorescein angiography
Other names	Fluorescent angiography
ICD-9-CM	95.12
MeSH	D005451
	[ edit on Wikidata]

Last updated March 16, 2022

Fluorescein angiography^[1] (FA), fluorescent angiography (FAG), or fundus fluorescein angiography (FFA) is a technique for examining the circulation of the retina 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 light at a wavelength 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.

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 520–530 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 arm or hand
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 with optic nerve head drusen, astrocytic hamartoma, 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 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 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.^{[ citation needed ]}

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 retina, choroid, optic disc, and iris.^[3] Among the common groups of ophthalmologic disease, fluorescein angiography can detect diabetic retinopathy (neovascularization), vein occlusions, retinal artery occlusions,^[4] 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.^[3]

Related Research Articles

The red-eye effect in photography is the common appearance of red pupils in color photographs of the eyes of humans and several other animals. It occurs when using a photographic flash that is very close to the camera lens in ambient low light.

The retina is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which translates that image into electrical neural impulses to the brain to create visual perception. The retina serves a function analogous to that of the film or image sensor in a camera.

Diabetic retinopathy, also known as diabetic eye disease (DED), is a medical condition in which damage occurs to the retina due to diabetes mellitus. It is a leading cause of blindness in developed countries.

Angiography or arteriography is a medical imaging technique used to visualize the inside, or lumen, of blood vessels and organs of the body, with particular interest in the arteries, veins, and the heart chambers. This is traditionally done by injecting a radio-opaque contrast agent into the blood vessel and imaging using X-ray based techniques such as fluoroscopy.

The choroid, also known as the choroidea or choroid coat, is a part of the Uvea, the vascular layer of the eye, and contains connective tissues, and lies between the retina and the sclera. The human choroid is thickest at the far extreme rear of the eye, while in the outlying areas it narrows to 0.1 mm. The choroid provides oxygen and nourishment to the outer layers of the retina. Along with the ciliary body and iris, the choroid forms the uveal tract.

Scanning laser ophthalmoscopy (SLO) is a method of examination of the eye. It uses the technique of confocal laser scanning microscopy for diagnostic imaging of the retina or cornea of the human eye.

Retinal hemorrhage is a disorder of the eye in which bleeding occurs in the retina, the light sensitive tissue, located on the back wall of the eye. There are photoreceptor cells in the retina called rods and cones, which transduce light energy into nerve signals that can be processed by the brain to form visual images. Retinal hemorrhage is strongly associated with child abuse in infants and young children and often leaves such abused infants permanently blind. In older children and adults, retinal hemorrhage can be caused by several medical conditions such as hypertension, retinal vein occlusion, anemia, leukemia or diabetes.

The central retinal artery branches off the ophthalmic artery, running inferior to the optic nerve within its dural sheath to the eyeball.

High-energy visible light is high-frequency, high-energy light in the violet/blue band from 400 to 450 nm in the visible spectrum, which has a number of biological effects, including those on the eye.

Dye tracing is a method of tracking and tracing various flows using dye as a flow tracer when added to a liquid. Dye tracing may be used to analyse the flow of the liquid or the transport of objects within the liquid. Dye tracking may be either qualitative, showing the presence of a particular flow, or quantitative, when the amount of the traced dye is measured by special instruments.

Central retinal artery occlusion (CRAO) is a disease of the eye where the flow of blood through the central retinal artery is blocked (occluded). There are several different causes of this occlusion; the most common is carotid artery atherosclerosis.

Fundus photography involves photographing the rear of an eye, also known as the fundus. Specialized fundus cameras consisting of an intricate microscope attached to a flash enabled camera are used in fundus photography. The main structures that can be visualized on a fundus photo are the central and peripheral retina, optic disc and macula. Fundus photography can be performed with colored filters, or with specialized dyes including fluorescein and indocyanine green.

Macular telangiectasia Disease of the retina affecting central vision

Macular telangiectasia is a condition of the retina, the light-sensing tissue at the back of the eye that causes gradual deterioration of central vision, interfering with tasks such as reading and driving.

Indocyanine green (ICG) is a cyanine dye used in medical diagnostics. It is used for determining cardiac output, hepatic function, liver and gastric blood flow, and for ophthalmic angiography. It has a peak spectral absorption at about 800 nm. These infrared frequencies penetrate retinal layers, allowing ICG angiography to image deeper patterns of circulation than fluorescein angiography. ICG binds tightly to plasma proteins and becomes confined to the vascular system. ICG has a half-life of 150 to 180 seconds and is removed from circulation exclusively by the liver to bile juice.

Microangiography is a type of angiography that consists of the radiography of small blood or lymphatic vessels of an organ. While most other types of angiography cannot produce images of vessels smaller than 200 µm in diameter, microangiography does just that. A microangiographic image is the result of injection of a contrast medium into either the blood or the lymphatic system and, then, enlargement of the resulting radiograph. Thus, an image is obtained in which there is contrast between vessel and surrounding tissue. It is often used in order to detect microvascular lesions in organs. But, it has been suggested that microangiography can also be used to detect tumors through visualization of tumor-induced small blood vessels. This is because tumor growths require vascularization before they can develop more rapidly. A few of the commonly used types are fluorescent, silicone rubber, and synchrotron radiation microangiography.

Bonnet–Dechaume–Blanc syndrome, also known as Wyburn-Mason syndrome, is a rare congenital disorder characterized by arteriovenous malformations of the brain, retina or facial nevi. The syndrome has a number of possible symptoms and can, more rarely, affect the skin, bones, kidneys, muscles, and gastrointestinal tract. When the syndrome affects the brain, people can experience severe headaches, seizures, acute stroke, meningism, and progressive neurological deficits due to acute or chronic ischaemia caused by arteriovenous shunting.

Branch retinal vein occlusion is a common retinal vascular disease of the elderly. It is caused by the occlusion of one of the branches of central retinal vein.

Optical coherence tomography angiography (OCTA) is a non-invasive imaging technique based on optical coherence tomography (OCT) developed to visualize vascular networks in the human retina, choroid, skin and various animal models. OCTA may make use of speckle variance optical coherence tomography.

Indocyanine green angiography (ICGA) is a diagnostic procedure used to examine choroidal blood flow and associated pathology. Indocyanine green (ICG) is a water soluble cyanine dye which shows fluorescence in near-infrared range, with peak spectral absorption of 800-810 nm in blood. The near infrared light used in ICGA penetrates ocular pigments such as melanin and xanthophyll, as well as exudates and thin layers of sub-retinal vessels. Age-related macular degeneration is the third main cause of blindness worldwide, and it is the leading cause of blindness in industrialized countries. Indocyanine green angiography is widely used to study choroidal neovascularization in patients with exudative age-related macular degeneration. In nonexudative AMD, ICGA is used in classification of drusen and associated subretinal deposits.

Sickle cell retinopathy can be defined as retinal changes due to blood vessel damage in the eye of a person with a background of sickle cell disease. It can likely progress to loss of vision in late stages due to vitreous hemorrhage or retinal detachment. Sickle cell disease is a structural red blood cell disorder leading to consequences in multiple systems. It is characterized by chronic red blood cell destruction, vascular injury, and tissue ischemia causing damage to the brain, eyes, heart, lungs, kidneys, spleen, and musculoskeletal system.

References

↑ Fluorescein+Angiography at the US National Library of Medicine Medical Subject Headings (MeSH)
↑ "Fluorescein angiography". U.S. National Library of Medicine. MedLine Plus. Retrieved 14 December 2012.
1 2 3 Kunimoto, Derek; Kunal Kanitkar; Mary Makar (2004). The Wills eye manual: office and emergency room diagnosis and treatment of eye disease (4th ed.). Philadelphia, PA: Lippincott Williams & Wilkins. p. 365. ISBN 978-0781742078.
↑ Kumar, Vinay (2007). "Chapter 29: Eye, Retina and Vitreous, Retinal Vascular Disease". Robbins basic pathology (8th ed.). Philadelphia: Saunders/Elsevier. ISBN 978-1416029731.

Additional references

Gisbert, Gisbert Richard; Gisele Soubrane; Lawrence Y. Yannuzzi (1998). Fluorescein angiography: textbook and atlas (2nd rev. and expanded ed.). Stuttgart: Thieme. ISBN 0-86577-712-8.
Kanski, Jack J. (2003). Clinical ophthalmology: a systematic approach (5. ed.). Edinburgh: Butterworth-Heinemann. ISBN 978-0750655415.
Manfred Spitznas: Understanding fluorescein angiography = Fluoreszeinangiografie verstehen. (German, English, Spanish) Springer, Berlin/Heidelberg/New York 2006, ISBN 978-3-540-30060-1.
Achim Wessing (1969). Fluorescein angiography of the retina.Textbook and atlas. Saint Louis: Mosby, ISBN 978-0801653889

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.

[1] Fluorescein+Angiography at the US National Library of Medicine Medical Subject Headings (MeSH)

[2] "Fluorescein angiography". U.S. National Library of Medicine. MedLine Plus. Retrieved 14 December 2012.

[WillsEye4th-3] 1 2 3 Kunimoto, Derek; Kunal Kanitkar; Mary Makar (2004). The Wills eye manual: office and emergency room diagnosis and treatment of eye disease (4th ed.). Philadelphia, PA: Lippincott Williams & Wilkins. p. 365. ISBN 978-0781742078.

[4] Kumar, Vinay (2007). "Chapter 29: Eye, Retina and Vitreous, Retinal Vascular Disease". Robbins basic pathology (8th ed.). Philadelphia: Saunders/Elsevier. ISBN 978-1416029731.

[1]

[2]

[3]

[4]