Tears to maintain the eye, especially the cornea and conjunctival tissue health has an important role, the main benefits of tears in the following areas: first, can play a role in flushing and cleaning the eye surface, the cornea and conjunctiva constitute the eye surface, directly exposed to the external environment, sand, smoke and dust with the flow of air, may be attached to the eye surface, endangering the health of the eye, tears can be flushed impurities off. Second, can play the role of nutrition of the cornea, the cornea in order to maintain the transparency does not contain blood vessels, oxygen and nutrients supply to rely on tears, tears to promote tear circulation, and constantly provide fresh oxygen and sufficient nutrients for the cornea. Third, can kill the bacteria on the eye surface, when the eye is contaminated, bacteria may attach to the eye surface, tears contain white blood cells and antibodies, can kill the bacteria on the eye surface in the process of tear flow, to avoid eye infection.