Intravenous Fluorescein angiography or Fluorescent Angiography is a technique
for examining the circulation of the retina and choroid using a fluorescent
dye and a specialized camera. It involves injection 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. The test uses the 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 applications of this
dye, all of which have a risk of severe adverse effects. See fluorescein safety
in health care applications. Fluorescein angiography does not involve the use of
ionizing radiation. 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 465-490 nm. Most only allow light through at a wavelength of 490 nm.
Barrier filter: Allows only yellow-green light 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 to increase contrast and often gives a better image
of the fundus than the color image. A 6-second bolus injection of 2-5cc 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. 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 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 since only one color is being
transmitted though the filter. Normal circulatory filling
times are approximate 0 seconds — injection of fluorescein
9.5 sec — posterior ciliary arteries 10 sec — choroidal flush
10-12 sec — retinal arterial stage 13 sec — capillary transition stage
14-15 sec — early 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, however, 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
hypofluroescence. Causes of hyperfluorescence:
window/transmission defects leaking defects
pooling defects staining
abnormal vasculature Causes of hypofluorescence:
blocking defect filling defect
Fluorescein angiography is used by physicians specializing in the treatment
of eye diseases 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, vein occlusions,
retinal artery occlusions, edema of the optic disc, and tumors. Additionally,
the transit time can provide an objective measurement of the rate of
blood flow through the imaged blood vessels.
Other types of fluorescent angiography Indocyanine green angiography
See also Fundus camera
References ^ Fluorescein Angiography at the US
National Library of Medicine Medical Subject Headings
^ "Fluorescein angiography". U.S. National Library of Medicine. MedLine
Plus. Retrieved 14 December 2012. ^ a b c Kunimoto, Derek; Kunal Kanitkar;
Mary Makar. The Wills eye manual: office and emergency room diagnosis and
treatment of eye disease.. Philadelphia, PA: Lippincott Williams & Wilkins. p.
365. ISBN 978-0781742078. ^ Kumar, Vinay. "Chapter 29: Eye, Retina
and Vitreous, Retinal Vascular Disease". Robbins basic pathology. Philadelphia:
Saunders/Elsevier. ISBN 978-1416029731. = Additional references=
Gisbert, Gisbert Richard; Gisele Soubrane; Lawrence Y. Yannuzzi.
Fluorescein angiography: textbook and atlas. Stuttgart: Thieme. ISBN
0-86577-712-8. Kanski, Jack J.. Clinical ophthalmology:
a systematic approach. Edinburgh: Butterworth-Heinemann. ISBN
978-0750655415.