“Red eyes” is one of the most common signs of various ophthalmic diseases, and can be caused by many conditions, such as “dry eyes”, “conjunctivitis “, “keratitis”, “keratoconjunctival foreign body”, “glaucoma”, and related allergic reactions, etc. Different diseases correspond to different causes, and the treatment taken for the fundamental treatment of the cause is also different. For example, the most common disease that causes red eyes is conjunctivitis, which can be classified as bacterial infectious, viral, and allergic for the cause, and the medication used for its treatment will also be selected according to the cause of its occurrence with different types, using different frequencies and using different lengths of treatment. Some diseases that cause eye redness require advanced medical treatment before further medication to achieve a more desirable outcome. For example, “foreign body in the conjunctiva” and “inversion of the eyelashes”. The most serious case is the “acute attack of acute angle-closure glaucoma,” in which the patient’s eyes are red, accompanied by eye swelling, headache, nausea and vomiting, and vision loss. To sum up, the mere manifestation of “red eyes” cannot be used as a basis for medical diagnosis and treatment independently.