Tunnel vision (top) is a less common defect, but potentially disastrous. The view straight ahead is fine, but peripheral vision is badly affected. The hazards of such a defect need no elaboration. Finally, some people suffer from double vision, which can greatly affect your judgement on the road. If you suffer from these or other defects, it is in your own interest, as well as that of all other road users, to do something about it.