Diabetes mellitus is a chronic metabolic disease. It has a great impact on vision. Diabetic retinopathy is the most common complication of diabetes, and the blindness rate of this disease is the first among fundus diseases. Therefore, diabetic patients should always pay attention to their vision changes. The effects of diabetes on the eyes are multifaceted. Most notably, it affects the retina and the lens. The lens can be sharply clouded and diabetic cataracts can appear in a few months or even days. Cataracts can be treated surgically, but caution is needed, and surgery should only be performed under comprehensive systemic conditions with good blood sugar control and must be reviewed regularly after surgery. There are many precautions to be taken during and after cataract surgery for diabetic patients, and patients must be consulted well beforehand to be well informed. Diabetic retinopathy requires early fundus examination, early diagnosis, and early treatment to preserve vision. Instead, delayed or delayed treatment can lead to advanced diabetic retinopathy, vitreous hemorrhage, neovascular glaucoma, and retinal detachment, leading to lifelong blindness. Diabetic patients do not have any eye discomfort in the early stage, but they cannot be ignored because there are no obvious symptoms of diabetes, and must be reviewed regularly. Therefore, the need for regular checkups is emphasized.