Visual loss causes different degrees of pain and loss to patients,and also gives a heavy load to family and society,so it is important to prevent visual loss.The prevention of visual loss is not only a part of public health undertaking,but also an important component of Ophthalmology.Generally speaking,vision rehabilitation is the main job for all the ophthalmologists.Epidemiology survey of visual loss mainly includes the research of the cause and the prevention method of diseases which cause visual loss,and to arrange and implement the prevention and cure of the vision loss.Now,the prevention of visual loss has become the main public healthy task in our country and in the world.