Yes, diabetes can sometiomes affect the eyes and cause poor vision. Diabetes are caused by the insufficient secretion of insulin which leads to high blood glucose and metabolic disturbance. Generally speaking, there are two main complications that diabetes affect on the eyes, that is, diabetic retinopathy, and diabetic cataracts. This is because that diabetes can impact the functions of the small blood vessels around the eyes and lead to eye arteriosclerosis. People who have diabetes get the chance of blindness ten to twenty-five times more than those people who have not diabetes. Therefore, for people who have diabetes, it is vital to control their levels of blood pressure, blood glucose, as well as blood lipid. In addition, if the people with diabetes are diagnosed as diabetic cataracts, then they may have to take an eye surgery.