Fundus fluorescence angiography is an examination method in which a dye that produces fluorescence is rapidly injected into the blood vessels and observed or photographed with a fundoscope or fundus camera with a color filter. Because the dye runs with the blood flow, it can outline the shape of the blood vessels dynamically, and the fluorescence phenomenon improves the contrast and visibility of the blood vessels, so that some subtle vascular changes can be identified; the blood supply pathways and vascular morphology of the choroid and retina are different, so the lesions of these two layers can be identified during the imaging; choroidal fluorescence can set off the condition of the retinal pigment epithelium; damage to the vessel wall, pigment epithelium and retinal The damage to the barrier of blood vessel wall, pigment epithelium and retinal inner boundary membrane can cause leakage of dye, so that many conditions that cannot be found by fundoscopy alone can be examined. Moreover, the use of fluorescent fundus camera to take continuous pictures makes the fundus examination results more objective, accurate and dynamic, thus providing valuable basis for clinical diagnosis, prognosis evaluation, treatment, efficacy observation and exploration of pathogenesis. I. Fundus examination and preparation before operation: The fundus should be examined in advance with fundoscope, anterior mirror or triple-sided mirror according to the situation, and the patient should be asked about the history of cardiovascular, liver and kidney diseases, allergic reactions and drug allergy, and the patient should be informed that fluorescein can cause nausea, vomiting, urticaria, hypotension, temporary yellowing of the skin and other reactions. The drug is excreted via urine after 24 to 48 hours, thus the urine can turn yellow. Fully dilate the pupil. Prepare various first aid supplies such as 1:1000 epinephrine, adrenocorticotropic hormone for injection. Promethazine, aminophylline and alamine, etc., in case of urgent need. Second, the operation steps: in the dark room. Firstly, observe the fundus examination site under the blue light wave, pay attention to the presence of false fluorescence. In order to observe whether the patient has any allergic reaction to fluorescein, first take 0.5ml of 10% sodium fluorescein and add 4.5ml of sterile isotonic saline to dilute it as a prediction test, slowly inject it into the anterior elbow vein and ask the patient what is the discomfort. If there is no adverse reaction, a syringe containing 5ml of 10% sodium fluorescein or 2.5-3ml of 20% sodium fluorescein can be switched and injected rapidly into the elbow vein within 10 seconds, the injection should be fast but not leaky so that the sodium fluorescein entering the blood vessel can reach a high concentration of visualization soon. If fluorescence fundus photography is done, color fundus photos and black photos without filter should be taken before injection, and fluorescence fundus camera equipped with filter system should be used to take photos immediately after the injection of fluorescein sodium into the anterior elbow vein for 5-25 seconds, and the time interval between photos depends on the condition. Fluorescence imaging analysis 1, arm-retina circulation time (A-Rct) fluorescein from the anterior elbow vein injection, through the right heart → left heart → aorta → common carotid artery → internal carotid artery → ophthalmic artery and to the fundus, for 7-12 seconds (but there are also up to 15-30 seconds), the difference between the two eyes should not exceed 0.5-1 seconds. 2. Staging of retinal blood circulation and fluorescence pattern Fluorescein sodium flows into the ciliary artery and central retinal artery system through the ophthalmic artery, and the latter in turn flows from the central retinal artery trunk → small artery → capillary network → small vein → central retinal vein → ophthalmic vein. In different stages, scholars at home and abroad have different staging methods, Hayreh staging is: (1) Pre-retinal artery stage: In this stage, the choroid first appears map-like fluorescence, the optic disc appears light hazy fluorescence color, if ciliary retinal artery exists, it also shows fluorescence. (2) Retinal arterial phase: seen after the choroidal vessels fill for about 0.5 to 1 second and are rapidly distributed to the entire arterial system within 1 to 2 seconds. The dye first becomes axial flow in the center of the blood column and is divided into 2 strands at the branches, each flowing along one side of the branch, forming one side fluorescent and one side non-fluorescent, called arterial laminar flow. The veins within this system do not fluoresce at all. (3) Retinal arteriovenous phase: The retinal arterioles are completely filled and the capillaries are reticulated. When one or several small veins filled with dye enter the large vein, the dye flows along the edge of this side of the vein in the direction of the optic disc and fluoresces on one or both sides of the vein while the center does not fluoresce, which is called venous laminar flow. The main manifestation of this phase is that the concentration of dye in the arteries and veins is relatively uniform and consistent. (4) Retinal vein phase: the arterial fluorescence concentration gradually decreases or disappears after 1~2 seconds, while the venous fluorescence is uniform and consistent. (5) Late stage: It is 10-15 minutes after the injection of sodium fluorescein, and there is still faint residual fluorescence in the veins. (3) Fluorescence pattern of choroidal blood circulation: Between 0.5 and 1 second before the fluorescence enters the central artery on the God’s disc, it first shows blurred splotchy fluorescence around the macula, and as the fluorescein enters the retinal vessels, then the whole background, except the macula, shows strip, patchy and reticular background fluorescence. Due to the thicker pigment epithelium in the macula, denser choroidal pigment and more lutein in the retinal neuroepithelial layer, the choroidal fluorescence is not visible in the macula under normal circumstances, which is called macular dark area. 4, optic disc fluorescence morphology: (1) deep hazy fluorescence, appearing in the pre-artery, a fuzzy bright spot, not exceeding the scope of the optic disc. (2) Superficial grape-like fluorescence, which appears in the early arterial phase, with brighter fluorescence, and can distinguish capillaries, not exceeding the optic disc. (3) Superficial radiolucent capillary fluorescence on the optic disc: appears in the arteriolar phase and exceeds the optic disc area. It is approximately in the area within 1/2 to 1PD outside the optic disc rim. (4) Late optic disc halos, appearing in the late contrast phase, with curved or ring-shaped faint fluorescence whorls at the optic disc margin, the extent of which always does not exceed the optic disc margin. (5) Abnormal fundus fluorescence (1) Self-fluorescence: It refers to the fluorescence that appears on the photographs taken before the injection of contrast agent due to the high reflectivity of white fundus sites (such as optic disc, lipid deposits, myelinated nerve fibers, choroidal atrophy spots, white protrusions, white scleral exposure areas, etc.) on the photographs. (2) Pseudo-fluorescence: It is caused by the inappropriate combination of excitation and barrier film, and the blue cyan light transmitted in the overlapping area of the two wavelengths. (3) Hyperfluorescence, i.e., enhanced fluorescence, is commonly seen as follows: ① Translucent fluorescence, characterized by the appearance of the choroidal fluorescence at the same time as the early choroidal fluorescence, with little or no change in size, shape, and brightness, and disappears with the disappearance of the choroidal fluorescence, due to depigmentation or atrophy of the pigment epithelium and enhanced transmission of choroidal fluorescence. It is also called “window defect”. Abnormal vascular fluorescence due to inflammation, tumor, trauma, degeneration, and congenital anomalies (neovascularization, microangioma, capillary dilation, collateral circulation, vascular short circuit, and double circulation, etc.). (3) Leaks: characterized by the appearance of leaks during the arteriovenous phase, with a gradual increase in their extent and consequent increase in their brightness, and persisting for several hours after the retinal choroidal fluorescence has faded, due to the destruction of the retinal vascular endothelial and pigment epithelial barriers and the penetration of the dye into the tissue interstices, forming leaks, which may appear as pooling or as tissue staining ( staining). (4) Hypofluorescence, i.e., diminished or absent fluorescence. There are two types of manifestations, one is blocked flouresc-ene, such as intravitreal and retinal hemorrhage, exudation, mechanized membrane, tumor, degeneration, etc. can obscure the retinal and choroidal fluorescence. The second is filling defect, due to any cause of fundus blood circulation disorders, fluorescence can not reach the supply area, resulting in reduced fluorescence filling, or even completely absent.