Red eyes are commonly caused by subconjunctival hemorrhage or conjunctival congestion due to eye diseases. Subconjunctival hemorrhage occurs mostly due to mechanical injuries such as eye rubbing, collision, vascular sclerosis, or coagulation dysfunction, which is manifested as a hemorrhagic redness in the white of the eye. Eye congestion is often seen in localized eye lesions, including conjunctivitis, uveitis and other ocular inflammation due to infection, allergy, autoimmune factors, or acute attacks of glaucoma due to a sudden and sharp rise in intraocular pressure, eye trauma due to collision of the eyes, etc., which is manifested as an increase in the redness of the whites of the eyes. It is recommended that patients seek timely medical treatment, according to different causes, targeted treatment.