The sudden appearance of redness in the right eye depends on the specific symptoms to determine what the problem is. First, if there is only a patchy or dotted redness in the eye, with no other symptoms and no pain, it is usually a sign of subconjunctival hemorrhage, which refers to the rupture of the subconjunctival capillaries due to various reasons, and therefore leads to the occurrence of such symptoms. Second, if in addition to eye redness, accompanied by pain, vision loss, increased eye discharge, generally considered to be a local inflammatory disease, such as conjunctivitis, keratitis or wheals, this situation requires early anti-infection treatment to avoid aggravation of the condition. Third, if the eyes suddenly appear red, and accompanied by swelling and pain, vision loss or ipsilateral dizziness, headache, this may be a manifestation of glaucoma, to go to the hospital as soon as possible to check clearly.