Dry eyes

Dry eyes are medically called "eye conjunctival desiccation". It is not a single disease, but a group of diseases characterized by dry eyes and less tears caused by several completely different causes. They have different causes, pathological processes and clinical manifestations. "Dry eye disease" or dry conjunctiva, keratitis is a disease caused by the lack of quality or quantity of the precorneal tear film, the conjunctiva and corneal epithelium cannot maintain normal function. The tear film is composed of a very thin surface lipid layer 10.5 mm and a layer of water rich in polysaccharide protein and mucin. The lipid layer has the effect of retarding the tear film evaporation. Under 30% relative humidity, the tear film evaporation rate is 3 m / h. When the humidity is high, the evaporation is reduced, and when it is dry, Evaporation increases.