Old tears may be some physiological phenomenon, but also may be the manifestation of certain diseases, such as conjunctivitis, keratitis, tear duct obstruction, etc., should be timely consultation to identify the cause of the disease. 1. Physiological factors: for example, long hours of playing cell phones, watching computers lead to excessive eye strain, there will be tears. 2. Pathologic factors: (1) Conjunctivitis: infection, allergy, physical and chemical stimulation and other causes lead to conjunctival inflammation, which will lead to symptoms such as redness and swelling of the eyes, itchy eyes, photophobia, increased secretions, and constant tearing. (2) Keratitis: generally caused by bacterial infection and viral infection. The cornea is located in the forefront of the eye, in direct contact with the outside world, and is susceptible to damage by microorganisms, trauma and physical and chemical irritants and inflammation. Clinical manifestations include blurred vision, pain, photophobia and old tears. (3) Lacrimal duct obstruction: Obstruction in any part of the lacrimal duct will cause tearing. If the old tearing cannot be relieved by resting, you should consult the doctor for examination as early as possible to clarify the cause of the disease, and follow the doctor’s instructions to carry out the appropriate treatment if necessary.