Vitamin A deficiency is a systemic disease caused by lack of vitamin A in the body. Its main pathological change is keratin degeneration in the epithelial tissue of the whole body. Eye symptoms appear early and significantly, with reduced dark adaptation ability, followed by dry conjunctiva and cornea, and finally corneal softening and even perforation. Therefore, it is also known as night blindness, xerophthalmia and keratomalacia. This disease is more common in infants and young children with malnutrition and long-term diarrhea. The peak incidence is mostly between 1 and 4 years old, and it is less common over 6 years old. This disease is common in developing countries in Asia and Africa, and it is not uncommon in remote areas of my country.