The pulling unit crew was running rods in the hole from the derrick. The rig operator raised the rod string and began to lower the rods into the well. With the rod transfer still in place on the rod triple, the blocks were lowered, causing the chain holding the rod transfer to break. The rod transfer then fell and struck an employee, who was standing on the work floor, on the top frontal area of his hard hat resulting in the loss of an eye.