Fluorescein angiography, or fluorescent angiography, is a technique for examining the circulation of the retina using the dye tracing method. 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 fluorescein dye also reappears 12-24 hours in the patient urine, causing a yellow-green appearance.
With the Fluorescein angiography ophthalmologic diseases such as , diabetic retinopathy, vein occlusions, retinal artery occlusions, edema of the optic disc, and tumors are examined.
Digital Fundus Camera Technique:
We inject 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 (approximately 10 seconds after injection). A filter is placed in the camera so only the fluorescent, yellow-green light (530 nm) is recorded.
Black-and-white photos give better contrast than color photos, which aren’t necessary since only one color is being transmitted though the filter.
Pathologic changes are recognized by the detection of either hyperfluorescence or hypofluroescence.
Causes of hyperfluorescence:
Leaking defects (i.e. capillary leakage, aneurysm, neovascularization)
Transmission (filling) defects
Causes of hypofluorescence:
Blocking defect (i.e. blood)
Filling defect (capillary blockage)