What do you mean by fundus angiography? Let’s start with the experience of old man Zhang, who lives in Hu Tai. Zhang is 70 years old and has been suffering from diabetes for more than 10 years. Some time ago, he suddenly felt that his right eye vision had decreased, and he went to the ophthalmology department to find out that his eyes had a problem with the fundus. So the doctor arranged a fundus angiogram for Zhang, and according to the results, the root cause of the disease was quickly found, and fundus retinal photocoagulation treatment was performed. Two months later, Zhang’s fundus improved significantly, and the vision in his right eye improved from 0.1 to 0.5. So what is fundus angiography all about? Why can it help find the root cause of fundus disease? Fundus angiography is called fluorescein fundus angiography, which is essentially a photograph of the fundus. Why is it necessary to take pictures of the fundus? Because the retinal arteries and veins in the fundus are some of the few blood vessels in the body that can be directly observed, and by looking at these vessels, many diseases of the fundus can be diagnosed and treated. However, if we look at the fundus directly, we can only see a static situation of the fundus. If we compare the fundus to a big river, and one day the river breaks its banks and floods the surrounding villages, we can only see the ocean, not knowing how and where the flood came from. Fundus fluorescence angiography is the rapid injection of a special non-toxic dye into the blood vessels and the application of a camera with a color filter for fundus photography. Because the dye runs with the blood flow, it dynamically outlines the shape of the blood vessels and, together with the fluorescence phenomenon, improves the contrast and visibility of the vessels, allowing some subtle vascular changes to be identified. Let’s go back to the big river under the eye. If we pour in some pigments to change the color of the water at the upstream of the river and then follow the water flow, we can easily follow the dyed water flow to find where exactly the big river broke its banks, how big the breach is, how serious the leakage is, how big the flooding area is and so on. This is the most basic principle of fundus angiography. With fundus angiography, we can find the cause of fundus disease and then treat it with the right medicine. The most common causes of fundus vasculopathy are either leakage or ischemia. We can find the leakage point through angiography, and then we can use fundus laser to close the leakage point for treatment. If it is ischemia, the river is blocked, we can apply some thrombolytic drugs or blood-stasis activating drugs to unblock the blood vessels for treatment. As the saying goes, there are three poisons in a medicine. Do those dyes that are injected into the blood vessels have toxic effects? Doctors will tell you responsibly that the fluorescein sodium and indocyanine green used in fundus angiography are non-toxic dyes, which may occasionally cause allergic reactions such as nausea, vomiting, dizziness, etc. After the angiography, the skin may turn yellow and the urine may be yellow-green due to the systemic distribution of the dyes and renal excretion, but they can be excreted completely after 24 hours, so there is no need to worry.