Fluorescein angiography is an objective diagnostic method in ophthalmology that allows you to register the circulation of fluorescein in the vessels of the inner shell of the eye. The technique makes it possible to identify functional and organic changes, to determine the structure and localization of focal lesions of the retina. It is used to study the architectonics of blood vessels, the nature of blood flow and to assess the functioning of the hematoretinal barrier. The study is carried out with contrast in the conditions of drug cycloplegia. Fluorescence angiography is performed independently or in combination with other diagnostic procedures.
Fluorescein angiography is used in patients with retinopathy on the background of diabetes mellitus. The effectiveness of using the technique in senile macular degeneration or occlusion of the vessels of the inner shell of the eyeball has been proven. The study is indicated for juvenile angiopathy and external exudative retinitis. The diagnosis is advisable for angiomatosis or serous etiology of retinal detachment. Less often, angiography is performed with complications of high-grade myopia or pathology of the optic nerve. The technique is informative for pathological neoplasms of intraorbital localization.
The study is recommended for patients with inflammatory chorioretinitis or congenital chorioretinal dystrophy. Fluorescein angiography is performed for Grenblad-Strandberg syndrome or symptoms of degenerative-dystrophic changes in the inner shell of the eye. The technique makes it possible to identify the primary signs of conjunctival neoplasms, rubeosis or iris tumors. An absolute contraindication to fluorescein angiography is individual intolerance to fluorescein, signs of hemorrhage in the vitreous or anterior chamber of the eye. With a burdened allergic history, it is necessary to conduct a prick test with an allergen before the study.
The procedure is carried out under conditions of drug-induced mydriasis. To achieve it, instillations of sympathomimetics are used. The study is carried out in a sitting position. Ophthalmological equipment is installed (a fundus camera with a mydriatic or non-mydriatic mode or a special scanning ophthalmoscope). The apparatus for fluorescein retinal angiography is positioned in such a way that it is possible to carry out movements in all four directions. During the diagnosis, the patient should focus his gaze in the desired direction.
Methodology of conducting
The first stage of fluorescein retinal angiography is color photographing of the fundus, followed by shooting in monochromatic shades. A control image is necessary to detect autofluorescence. The dye is injected parenterally into the ulnar vein. To track the progress of the contrast, at the time of the injection, turn on the chronometer and take the first picture. After the dye is visualized in the fundus area, the images are taken with a frequency of 1 in 1-2 seconds. The recommended rate of introduction of the entire volume of the dye is 8-10 seconds. At the time of completion of the injection, the manipulation room should be dark.
After receiving 5-6 angiographic images, pictures of the second eye are taken. The last series of images is carried out 5 minutes after the introduction of the dye. After 10, 15 and 30 minutes, delayed photos are taken. Retinal angiography can be divided into the following stages: choroidal, arterial, early and late venous and recirculation. The first phase occurs in an average of 10 seconds and lasts 0.5 minutes. Initially, the capillaries of the vascular membrane are colored unevenly. After visualization of laminar blood flow in the venous network area along the periphery of the optic nerve disc, the staining becomes uniform. Exceeding the rate of dye administration may be accompanied by dyspeptic phenomena, nausea, vomiting or headache. During the first 24 hours after the end of the procedure, transient staining of urine, skin and mucous membranes is possible.
Interpretation of results
Normally, the internal hemoretinal barrier is impervious to the dye. The release of fluorescein into the interstitium indicates damage to the vascular wall. Physiological areas of hypofluorescence are isolated. Due to the fact that there are no vessels in the central foveolar zone, it is not displayed on the fluorescein angiography of the retina. If there is an obstacle between the glow source and the device, fluorescence shielding is noted. A change in the transparency of the optical media of the eye leads to a violation of the transmission when performing fluorescein retinal angiography. At the same time, anomalies of the structure or pathology of the vascular wall cause abnormal perfusion.
Pathological enhancement of fluorescence indicates occlusion of a vein or epiretinal membrane, formation of anastomoses or signs of angiogenesis. Hyperfluorescence is observed in patients with vascular aneurysms or damage to the pigment layer. If a widespread amplification is visualized on the fluorescein angiography of the retina, this indicates a decrease in the intensity of fundus pigmentation, which may be an individual feature of the structure or a sign of albinism.