This arises when two refractive errors occur on the eye. This is an inherited trait which inhibits the development of the eye. It can also be as a result of accidents, operations or incidents where the eye sustains damage.
Assuming that the problem is not too acute, toric contact lenses or spectacles can rectify the problem. It can also be treated surgically through excimer laser treatment (LASIK or PRK), often in combination with the treatment of other optical problems. Irregular astigmatism may also arise and specially-cut spectacles may not help with this problem. The majority of people suffer from some form of irregular astigmatism to differing degrees, but only wave-fronted steering lasers can adequately treat this problem.