The revelation of the possible trouble with his eyes added a new element to the emerging portrait of the 27-year-old German pilot, who the authorities say was also being treated for psychological issues and had hidden aspects of his medical condition from his employer. Lubitz, the co-pilot, was alone in the cockpit of the Airbus A320 jetliner on the flight from Barcelona to Dusseldorf, ignoring demands from the captain to be let back in, when the plane crashed. [...] investigators in Germany and France, airline regulators, political leaders and the families of the victims have sought answers about what might have led Lubitz to do what he did.