My father has conjunctivitis.please tell me how to cure it without any medicine ?

Eye doctor: See an eye doctor, some conjunctivitis can result in permanent damage and even blindness. If this is not possible, you can rinse and clean the eyes with sterile water or commercially prepared eye wash, use artificial tears to lubricate and rinse out the eyes every 1-3 hours, use good hand and face hygiene. With time it should run its course and resolve.