Shares in Italy’s Luxottica (LUX.MI) fell as much as 10 percent on Monday after the abrupt resignation of its second chief executive in as many months, fuelling concern over tensions at the top of the world’s biggest eyewear group. The maker of Ray-Ban and Oakley sunglasses announced on Sunday that co-CEO Enrico Cavatorta planned to leave – just six weeks after the unexpected departure of his predecessor, veteran Andrea Guerra, credited with expanding Luxottica abroad. Luxottica provided no explanation for Sunday’s departure.