Astigmatism

Patients with astigmatism see objects as distorted at any distance. The image of a dot-like object in nature is perceived as a line and represented as such on the retina. Usually the reason for this condition is the shape of the cornea, which under these circumstances resembles the shape of an egg rather than the shape of a ball. Because of the different curvatures of the cornea, the light is then for example bent stronger vertically than horizontally. Consequently, the image is distorted.

The optical correction is made by adjusting the curvature of the cornea or rather by an approximation of the corneal surface to a spherical shape, so that the incoming light beams once again are gathered in one single focal point.

Eyeglasses and contact lenses achieve this correction with so-called cylindrical glasses, which are positioned in front of the eye in a specifically defined direction. This is why the corrective value of eyeglasses and contact lenses is given in dioptre for the cylinder value and in degrees for the position of the cylinder axis. Your prescription will then for example read a cylinder value: cyl. -2.5 dpt., axis 75º. If surgery is performed, the refractive power of the cornea is altered to obtain optimal condition.

Astigmatism often occurs in combination with myopia or hyperopia. The correction value is indicated in dioptre as well.