There are many causes of ocular dryness syndrome, such as autoimmunity, chronic conjunctivitis and toxic effects. 1. Autoimmunity: autoimmune factors can reduce tear secretion after involving the lacrimal gland, thus leading to the occurrence of ocular dryness syndrome. 2. Chronic conjunctivitis: in patients with chronic conjunctivitis, inflammation can destroy the secretion glands of the conjunctiva itself or involve the lacrimal gland, thus leading to the occurrence of ocular dryness syndrome. 3. Toxic effects: eye contact with poisons can lead to damage to the eye surface and lacrimal gland dysfunction, resulting in a lack of mucus protein in the tears and a decrease in tear secretion, which can lead to the occurrence of ocular dryness syndrome. There are many other reasons that can lead to the occurrence of ocular dryness syndrome, it is recommended to go to a regular hospital, consult a professional doctor, and cooperate with the doctor to complete the relevant examinations, to clarify the causes and avoid blind treatment.