One of the challenges of being an owner of binoculars is keeping them from being knocked out of line. The key to image quality is having the two barrels perfectly in line with each other. If binoculars are dropped and an internal lens or the barrel crossbar is displaced evenly slightly, the result is a pair of binoculars that give you eye strain and a headache. Repairing binoculars can be cost prohibitive, but there is a solution: buy a pair of binoculars with a lifetime guarantee! Even companies selling modestly priced binoculars (e.g. Vortex) now provide this wonderful service.
How do I know if my binoculars are out of line? (alignment)