In addition to primary tear deficiency, keratitis sicca can also be seen in the following situations: 1. Chronic diseases such as endocrine diseases, anemia, and vitamin deficiency. 2. Acute diseases such as acute exfoliative dermatitis, Stevens-Jonhnson syndrome, and ocular pemphigoid. 3. Trauma and surgery of the eyelids and conjunctiva may damage the ducts of most basic and reverse secretion organs. Primary tear deficiency is usually referred to as syndrome in clinical practice. It is divided into two types: broad and narrow. The so-called broad syndrome (abbreviated as SJS) refers to other systemic and autoimmune diseases (such as rheumatoid arthritis) in addition to dry mouth and eyes. The narrow SJS is keratitis sicca (abbreviated as KCS).