Highmark, parent company of Eye Care Centers of America (ECCA), Davis Vision and Viva International, has agreed to merge with another health insurance company in Pennsylvania, Independence Blue Cross (IBC). The new company that will come out of the merger will maintain dual headquarters in Pittsburgh and Philadelphia, employing some 18,000 people in the state. Kenneth R. Melani, managing director, president and chief executive of Highmark, will be the CEO of the combined company. Joseph A. Frick, IBC's president and chief executive, will be president and chief operating officer. Walter D'Alessio, chairman of IBC, will be the new company's chairman. J. Robert Baum, chairman of Highmark, will act as vice chairman.