St. Valentine was a priest in Rome who was martyred in the year 259 A.D. He had defied Emperor Claudius’ decree that no marriages were to take place (so young men would be free for a war effort) and was found out and arrested. Claudius, after hearing that St. Valentine was making converts in prison, after a blind girl was healed through his prayers, had him tortured, beaten, and beheaded. He is counted as an intercessor for persons with epilepsy. (Personally, though, given the fact that he healed a blind girl in prison, I would ask his intercessions if I had visual impairments.)
His Feast Day in the Orthodox Church (as well as in popular American culture) is February 14.