The main causes of red and painful eyes are as follows:1. Acute conjunctivitis, including acute bacterial conjunctivitis, viral keratoconjunctivitis, and fungal conjunctivitis.2. Keratitis, including bacterial keratitis, viral keratoconjunctivitis, and fungal keratoconjunctivitis.3. Acute attack of glaucoma, when acute angle-closure glaucoma, the patient manifests mixed congestion, eye distension, pain, and blurred vision, and accompanied by nausea and vomiting. 4, acute iridocyclitis, the patient manifests photophobia, pain, eye redness, blurred vision. 5, scleritis, when the patient’s eye pain is obvious, and accompanied by limited congestion of the conjunctiva. Therefore, when red eyes, eye pain should be timely to the regular eye care institutions to determine the cause of eye redness and pain, and appropriate treatment to avoid delays in the condition.