Patients with one red eye and one normal eye may be caused by bacterial infection leading to keratitis or conjunctivitis, and may also be related to eye trauma. 1. Keratitis: under the stimulation of inflammation, patients with keratitis may have conjunctival congestion, which is manifested as redness of the eyes, patients can follow the doctor’s instructions to use ganciclovir eye drops, levofloxacin eye drops and other medications, to control inflammation, and to promote the recovery of the condition. 2. Conjunctivitis: Conjunctivitis is caused by bacterial and viral infections, and patients may experience conjunctival congestion, photophobia, foreign body sensation, and increased secretion and other uncomfortable symptoms. Patients can follow the doctor’s instructions through the levofloxacin eye drops, tobramycin eye drops and other drugs to promote the recovery of the condition. 3. Eye trauma: eye trauma patients in the mechanical stimulation, can also appear uniocular conjunctival congestion, manifested in one eye red, patients can also appear eye pain, bleeding and other symptoms. It is recommended that patients with obvious eye congestion consult a doctor in time to assess their condition and follow the doctor’s instructions for treatment.