Hi...., there are various causes for painful red eye....Some of the causes include, Acute conjunctivitis, acute angle closure glaucoma, acute iridocyclitis, chemical or mechanical injury to the eye ball etc....., Treatment options mainly depends upon the underlying cause.... These conditions can sometimes be serious and could threaten your sight, so they should be assessed by a doctor as soon as possible.....Kindly consult your ophthalmologist for further evaluation and treatment....