The astigmatism is an ametropia, which makes you see a dot distorted like a line. Often the astigmatism goes along with a myopia or hyperopia. It is rarely possible that only an astigmatism is existent. An astigmatism is no disease of the cornea! Astigmatism can occur because of two different curvatures of the cornea. That means that the cornea is curved different in two meridians which are in 90 degrees to each other. In contrast the astigmatism can occur due to different curvatures of the ocular lens. This is called interior astigmatism. In most cases there is a combination of both types. And this is a regular astigmatism. If the cornea is shaped irregular, e.g. as a consequence of an injury or disease, you call it irregular astigmatism.
Correction of the astigmatism
The eye cannot compensate the astigmatism by itself. But the influence is only little or not noticeable if the value is low and then there is no need to correct the astigmatism. If the astigmatism is corrected for the first time the vision can be unusual at first, because the brain was trying to compensate the distortion before. But after a short while you achieve a comfortable and exact vision.
The most popular correction of the regular type are glasses. Therefore a so called toric spectacle lens is used, which has different values in two meridians which are in 90 degrees to each other. And that’s why the astigmatism is corrected. The irregular type can only be corrected in parts by glasses or even not at all.
An astigmatism can also be corrected by contact-lenses. With high astigmatisms and the irregular type a good vision can only be achieved by contact lenses. The correction by contact lenses can be in different ways, e.g. by toric contact lenses.
Even an astigmatism can be corrected by refractive surgery. But only low astigmatisms up to 2 dpt can be corrected properly and have reliable results.