The procedure of fluorescence angiography (synonyms: fluorescence angiography – FA, FLA, FAG), which is largely based on the research work of Prof. Achim Wessing, is used to detect diseases of the fundus of the eye. Fluorescence angiography is one of the imaging methods and is based on the principle of visualizing the retinal vasculature (retina) using a fluorescent dye.
Indications (areas of application)
- Age-related macular degeneration (AMD) (The macula, also called the yellow spot, represents a 2-mm area on the retina that has the greatest density of photoreceptors and is therefore necessary for sharp vision. Macular degeneration is a retinal disease of the eye that particularly affects older people. It causes the central visual field (visual area without movement of the eye muscles) to be considerably reduced or to fail completely due to an insufficiency (functional weakness) of the pigment epithelium, which leads to a reduced breakdown of waste products (dead cells). This leads to severe damage to the pigment epithelium. The affected person sees overall no longer sharp, distorted, colors fade, extreme glare sensitivity occurs and normal reading becomes impossible despite glasses).
- Diabetic retinopathy (damage to the retina due to an existing diabetes mellitus / diabetes).
- Vascular occlusion (here a distinction is made between arterial and venous occlusion. In the case of arterial occlusion, central retinal artery occlusion (main supply vessel of the retina) is particularly important because it is associated with rapid visual loss (loss of vision). However, far more often, especially in older age, there is occlusion of a central vein, in which the loss of visual acuity is not always complete and develops insidiously).
- Tumors of the retina (eg, retinoblastoma – a malignant retinal tumor occurring in childhood) and choroid (choroid – the choroid lying below the retina serves to nourish the retina).
The procedure
The basis of angiography represents the property of fluorescence, which is the ability of a molecule to emit light of a longer wavelength when it itself absorbs short-wavelength light rays. This ability is exploited, for example, in the substance fluorescein, which itself begins to glow when excited by light of a certain wavelength. Fluorescein angiography is performed in several steps and requires a sufficiently wide pupil. At the beginning of the examination, the retina is photographed in normal ambient light by means of a fundus camera and a red-free photo is produced by using filters. Subsequently, the attending physician performs an intravenous injection of fluorescein within a few seconds. Following this, the retina is photographed at one-second intervals over a period of approximately 20 seconds, allowing an assessment of the flow of fluorescein through the retinal vessels. Furthermore, control photographs of the other eye are taken. Fluorescein angiography has important diagnostic significance in the evaluation of circulatory disorders of the retina, making it the procedure of choice for diseases that affect it. Increased fluorescence indicates the following findings:
- A leak (leakage) in the retinal or choroidal circulation (retinal or choroidal circulation).
- Abnormal (malformed) blood vessels
Decreased fluorescence, on the other hand, indicates the following findings:
- Blockage or occlusion of the vascular system.
- Loss of vascular (belonging to the blood vessels) tissue.
- Pigment epithelial detachment (the layer of pigment epithelium (RPE) serves on the one hand as a light filter and on the other hand the exchange of substances with the photoreceptors of the eye, therefore, in the case of detachment, the exchange of substances is impaired and the photoreceptors are damaged).
Fluorescein angiography is of great importance in the imaging diagnosis of ophthalmology, as it can be used both in the detection and in the follow-up of the above-mentioned eye diseases.
