Astigmatism

The cause for astigmatism is a deviation of the cornea or lens. These are normally ball-shaped, however they are cylindrical by individuals with astigmatism. For this reason, there is a distortion from the point of refraction and thus the resulting line of refraction. The cylindrical alteration is thus determined by the steeper curvature of the cornea(or lens) and the axis in which it lay.

The regular astigmatism can occur alone or together in combination with near- or far-sightedness. Generally, it is already fully developed by childhood. If left untreated, astigmatism can result in a permanent weakened vision. The term "irregular astigmatism", is used for instance, in the case of corneal scarring.

Astigmatisms are corrected using cylindrical glasses. These are constructed in such a way, so that the refraction of the glasses and cornea (or lens) are added together, in order to place the focal point once again on the retina's surface.