For limited diabetic macular edema, laser is the treatment of choice, using the photothermal effect of laser to “burn” the “culprit” causing the edema, and the edema will slowly subside. However, for other types of macular edema, such as diffuse or cystic macular edema, laser treatment is not suitable, and vitreous cavity injection treatment is preferred, which is often referred to as intraocular injection, commonly used anti-VEGF drugs and glucocorticoids. The effect of anti-VEGF: the concentration of VEGF in the eye decreases, vascular permeability decreases, and edema disappears VEGF is the abbreviation of vascular endothelial growth factor, which has the effect of increasing the permeability of the blood vessel wall and inducing new angiogenesis. In patients with diabetic retinopathy, the concentration of VEGF in the vitreous cavity and around the blood vessels on the retinal surface is abnormally high, leading to retinal neovascularization and increased vascular permeability, resulting in the development of edema. The principle of intraocular injection of anti-VEGF drugs for the treatment of diabetic macular edema is to use drugs to make the concentration of VEGF in the eye decrease, which can inhibit neovascularization, and at the same time can make the permeability of blood vessels decrease, so that the exudation of blood vessels will be reduced, and the edema can slowly absorb and subside. However, anti-VEGF drugs have a certain metabolic time in the eye, and when the drug concentration is lower than the therapeutic concentration, edema will recur, so repeated treatment is needed. Role of glucocorticoids: inhibit inflammatory factors and make the edema subside In addition to the injection of anti-VEGF drugs, glucocorticoids can also be injected into the vitreous cavity. The cause of macular edema is not single, besides the increase of VEGF concentration in the eye, which makes the neovascularization and vascular permeability increase, another important factor is the presence of other inflammatory factors, which makes the macular edema persist and not recede. It is well known that hormonal drugs have anti-inflammatory mechanism, which can non-specifically inhibit many inflammatory factors and make the macular edema subside. However, like the injection of anti-VEGF drugs, hormones also need to be injected repeatedly. As diabetic retinopathy persists, the effect on retinal and choroidal vascular permeability persists, and both hormones and anti-VEGF drugs must be in effective concentration to work, and macular edema may recur after drug metabolism. How are the two drugs used? Both drugs are administered by vitreous cavity injection, and the number of injections is determined by the condition. Generally speaking, two or three days after the injection of anti-VEGF drugs, there will be a significant reduction of macular edema, and the thickness of the retina in the macula will be significantly reduced in about a week, and patients can feel that they can see more clearly than before the treatment, and their visual acuity has improved. Theoretically, the effect of the drug can last for one month, and the injection will be continued after one month. Many patients sound like there is no end to it and wonder if they have to keep on injecting. After the results of the current multi-center clinical trials and literature analysis (Lucentis injection), the number of injections in the first year is 8~10 times on average, and the number of injections in the second and third years decreases significantly, especially for patients after three years, some of them only need one or even zero injections per year. As for hormones, the usual dosage is 1 mg~4 mg each time, the higher the dosage the longer the maintenance time, and there are also extended-release dosage forms that can prolong the action time and the interval between injections. However, the higher the dosage of hormones, the higher the risk of side effects, the most common of which are elevated intraocular pressure and cataracts, as well as infections, all of which have serious effects on vision. Therefore, doctors will weigh the pros and cons and choose the appropriate dosage according to the patient’s condition.