Fluorescence angiography
Fluorescence angiography is an imaging technique used to diagnose diseases of the fundus (see angiography ). When the pupil is dilated with drugs, the influx and distribution of a suitable dye, for example fluorescein or indocyanine green , is documented. The dye serves as a contrast medium .
The entire examination process is divided into several phases: First, the retina is photographed under normal lighting ( color image ). This is followed by a recording with red-free light using green filter glass . This improves the contrast between the blood vessels and the surrounding retina . This recording is played back in grayscale like the following phases . After these preparatory recordings, the actual angiography phase begins. The flash light of the camera illuminated by a special (blue) Exciterfilter especially in the wavelength which excites the bulb to illuminate. The returning light has to pass a second barrier filter . This means that other interfering wavelengths than those of the excited light source are masked out. Now, before the dye is injected, such a fluorescence recording takes place in order to show so-called self-fluorescence phenomena . The solution is then injected intravenously and further recordings are made at fixed time intervals.
Among other things, the time between the injection and the appearance of the dye in the arteries of the retina and the distribution over time are evaluated . Usually recordings of the “arterial phase” (after about 20 seconds), the “venous phase” (after about 1 minute) and the “late phase” (after 5 to 15 minutes) are documented and assessed.
Fluorescence angiography is particularly helpful in ophthalmic diagnostics, for example in AMD (= age-dependent macular degeneration ), diabetic retinopathy , occlusions of blood vessels in the retina and tumors of the retina or choroid .
Achim Wessing is considered a pioneer of fluorescence angiography , who summarized the results of his research in 1968 in the textbook and atlas "Fluorescence Angiography of the Retina" , which has been translated into several languages.