Tears in the eyes of diabetic patients may be caused by diabetic retinopathy, glaucoma and dacryoadenitis. 1. Diabetic retinopathy: This disease is a common complication of diabetes mellitus, which is mainly caused by the damage of retinal microvessels due to the continuous elevation of blood sugar. Common risk factors include hyperlipidemia, pregnancy and smoking. Patients may have flying mosquito syndrome, showing symptoms such as tearing eyes, photophobia and blurred vision. 2. Glaucoma: This disease is also one of the complications of diabetes, because elevated blood glucose indirectly interferes with the circulation of atrial fluid in the eye, resulting in increased intraocular pressure, so glaucoma will occur. The disease is usually asymptomatic in the early stages, but as the disease progresses further, patients may experience symptoms such as tearing, headache, and eye swelling. 3. Dacryoadenitis: The occurrence of this disease is related to the immune response, pathogenic microbial infection and other reasons. If diabetes mellitus is combined with dacryoadenitis, it can lead to the manifestation of tearing eyes, and may also have symptoms such as pain, increased secretion and swelling of the lacrimal gland. There are many causes of tearing eyes in diabetic patients, and it is necessary to visit the hospital to clarify the specific cause of the disease.