With the improvement of people’s living standards, the incidence of diabetes mellitus (DM) is increasing year by year, and people have a preliminary understanding of the “three more and one less” of diabetes mellitus, i.e., drinking more, eating more, urinating more and losing weight, but they know little about the ocular complications of diabetes mellitus. The main complications of diabetes mellitus are: a. Refractive abnormalities caused by diabetes mellitus For diabetic patients, when the blood sugar rises, the lens of the eye hydrates and swells, the refractive power increases and becomes myopic; when the blood sugar decreases, the lens returns to its original state and becomes orthoptic; this change in the refractive power of the eye within a short period of time is a characteristic of diabetic refractive abnormalities. For example, some middle-aged and old-aged patients, who have already had blurred vision, suddenly look closer and clearer recently, should consider the possibility of diabetes and go to the hospital to check blood sugar and do the necessary external eye and fundus examination at the same time to prevent delay. Diabetic cataract Young type I diabetic patients are prone to diabetic cataract, which can be manifested as rapid vision loss within a short period of time and “snowflake” clouding of the lens, while in older type II diabetic patients, diabetes often accelerates the development of senile cataract. When the patient’s vision drops below 0.3, cataract extraction and IOL implantation should be considered to improve vision. However, blood sugar must be controlled before surgery. Diabetic retinopathy (DR) is the most serious ocular complication of diabetes. Its occurrence and development depends not only on the degree of metabolic disorder, but also on the age of diabetes onset, duration of disease, genetic factors and the degree of blood sugar control. Generally speaking, about 1/4 of diabetic patients have DR, and 5% of them develop proliferative diabetic retinopathy (PDR). According to statistics, 25% of patients with diabetes for more than 30 years develop PDR, of which 2-7% go blind as a result, and the 5-year mortality rate of patients blinded by DR is 30%, and the cause of death is often cardiac or renal complications of diabetes. The fundus of DR is characterized by microangioma, hemorrhage, exudate and other changes in the early stage, and neovascularization and membrane formation in the late stage, and eventually blindness due to tractional retinal detachment. Therefore, it is important for diabetic patients to go to ophthalmology regularly (every 3-6 months) for fundus examination and fundus angiography if necessary to detect lesions and treat them early to prevent serious consequences. Regarding the treatment of diabetic retinopathy, the efficacy of various drugs is currently variable. Laser photocoagulation is the easiest and most effective treatment today to maintain and improve the patient’s vision and reduce the risk of blindness. The method is non-invasive, painless, convenient, fast, and follows the treatment. Iris redness secondary to neovascular glaucoma This complication is the most serious consequence of DR. Patients can be blind with eye pain, headache, nausea, vomiting, once the occurrence of the need to choose destructive surgery to control intraocular pressure. Diabetic ophthalmoplegia is a diabetic microangiopathy that leads to ischemia and hypoxia of the cranial nerves. The incidence of the disease is relatively small. Patients may exhibit sudden onset of diplopia (one object seen as two), eye strabismus and ocular motility disorders, etc., and recover after treatment for 2 months or longer. Other symptoms such as dilated conjunctival capillaries, iridocyclitis, corneal hyperaesthesia, etc. The above examples of eye complications related to diabetes mellitus, I hope it can be helpful to diabetic patients.