Patients with tears in one eye and no tears in the other may be associated with dacryocystitis, tear duct obstruction, and difficulty in eyelid closure. 1. Dacryocystitis: Because of the obstruction of nasolacrimal duct, tear retention in the lacrimal sac, and secondary bacterial infection can cause inflammation of the lacrimal sac, and under the stimulation of inflammation, the patient suffers from tearing of the eye. 2. Lacrimal duct obstruction: patients with lacrimal duct obstruction may experience tearing because the tears cannot be discharged from the nasolacrimal duct into the nasal cavity through the normal route. 3. Difficulty in eyelid closure: Because of facial nerve palsy, the orbicularis oculi muscle of the patient may be flaccid, resulting in incomplete eyelid closure, causing the tear sac to expand weakly, leading to insufficient suction, because tears can not enter the tear ducts, the patient may experience tearing and other uncomfortable symptoms. It is recommended that patients with monocular tearing should consult a doctor in a timely manner to assess their condition and standardize treatment under the guidance of a doctor.