Keratoconjunctival dryness (keratoconjunctivitis sicca), also known as dry eye, is a general term for a variety of diseases characterized by abnormal tear quality or quantity, or abnormal kinetics resulting in decreased tear film stability, accompanied by ocular discomfort and/or ocular surface tissue lesions, from any cause. Currently, most scholars tend to believe that patients with symptoms of dry eye only, but it is transient and returns to normal after rest or brief application of artificial tears, and there are no signs of dry eye, especially no ocular surface damage, and no local or systemic causes of dry eye, this kind of condition is called dry eye. Those with both symptoms and signs are called dry eye disease, and those with combined systemic immune diseases are called dry eye syndrome. The pathological changes on the ocular surface, immune-based inflammatory response, apoptosis, reduction of sex hormone levels and the influence of external environment are the main factors in the development of dry eye, but the connection or causal relationship between these factors is not yet fully understood. The classification method proposed by the American Dry Eye Study Group in 1995 mainly classifies dry eye into two types: deficient aqueous production and over evaporation. The former is aqueous tear deficiency (ATD) due to lacrimal gland disease or malfunction, and can be divided into Sjogren’s syndrome (SS-ATD) and non-SS-ATD. The latter mainly refers to Meibomain gland dysfunction (MGD). The etiology is complex and can manifest as a primary disease, such as a possible association with autoimmune lymphocyte infiltration of the lacrimal and salivary glands, and a possible association with viral infections (EBV, HIV), as rapid development of ATD has been observed in patients with mononucleosis and HIV infection. ATD may also be secondary to other risk factors such as ocular infections, trauma, drug use, surgery, endocrine disorders, etc. For example, conjunctival scarring caused by trachoma or ocular chemical injuries can directly block the opening of the lacrimal duct in the upper dome, thus reducing tear production. In addition, ATD is often associated with many primary diseases such as Riley-Day syndrome, congenital atelectasis, lacrimal gland deficiency, ectodermal dysplasia, and Adie syndrome. Because of the complex etiology of dry eye and the intertwined effects, it has been advocated to classify dry eye into the following four types based on tear deficiency components: aqueous deficiency, mucin deficiency, lipid deficiency, and abnormal tear dynamics (distribution). The classifications of dry eye are not completely independent of each other; in fact, they often intersect or even coexist and rarely occur separately. Tear film related examinations] Tear film related examinations include the following a. Dry eye questionnaire scale A series of questions are designed to determine the presence of dry eye according to the presence and severity of common symptoms related to dry eye and the presence of related medical history, based on the summary score of the answers chosen by the patient. The advantages include convenience, economy, high specificity and sensitivity, and ease of screening for dry eye prevalence and initial screening for dry eye diagnosis in a large population. However, the diagnosis rate of borderline dry eye is not high, and it is difficult to analyze the specific influencing factors. In addition, the question and answer options of the current questionnaire are designed according to the western cultural background and living environment, which are not in line with the national thinking, so a standardized questionnaire in line with the national situation needs to be developed. Second, the width of the tear river The junction of the band of light projected on the surface of the cornea and the lower lid margin under the slit lamp is visible as the fluid level of the tear, and its width can reflect to some extent the amount of tear secretion. The width of the tear river measured clinically corresponds to the radius of curvature of the tear river, normal >0.5-1.0 mm, ≤0.35 mm is diagnosed as dry eye. Third, the tear secretion test (Schirmer test) is most commonly used and can be divided into two types, Schirmer I and Schirmer II, depending on the test method. Without ocular surface anesthesia, the secretion function of the main lacrimal gland is tested, while the secretion function of the secondary lacrimal gland (basal secretion) is tested after surface anesthesia, with the same observation time of 5 minutes. The normal value is 10 to 15 mm/5 min.