Dry eyes are a symptom of dry eye syndrome, which has become a common and important type of ocular surface disease affecting people’s quality of life. Dry eye is a type of disease that results in eye discomfort and visual dysfunction due to tear film instability and/or ocular surface damage caused by abnormalities in tear quantity or quality or fluid dynamics. The main risk factors are: old age, female, diabetes, pterygium, air pollution, high altitude, eye drop abuse, use of video screen terminals, keratoconus surgery, allergic eye disease and some systemic diseases. According to the pathogenesis of dry eye, dry eye can be divided into: (1) aqueous deficiency dry eye: caused by insufficient aqueous tear production and/or qualitative abnormalities, such as Sjogren’s syndrome and dry eye caused by many systemic factors; (2) evaporative excess dry eye: caused by qualitative or quantitative abnormalities of the lipid layer, such as blephar gland dysfunction, visual screen terminal syndrome, blepharitis, and incomplete eyelid closure (3) Mucin-deficient dry eye: caused by damage to the epithelium of the ocular surface, such as damage to the ocular surface from drugs, chemical toxicity, thermal burns, and corneal rim dysfunction; (4) Abnormal tear dynamics dry eye: caused by abnormal tear dynamics, such as transient abnormalities and conjunctival relaxation; (5) Mixed dry eye: is the most common type of dry eye clinically, caused by two or more of the above causes Dry eye. Dry eye is a kind of tear film instability and/or ocular surface damage caused by abnormal tear quantity or quality or fluid dynamics, which can be divided into 5 categories according to the pathogenesis, and the most common one is mixed type clinically.