Hornhautverkrümmung (Stabsichtigkeit)- das Sehen mit Hornhautverkrümmung
Astigmatism
People with astigmatism experience distorted vision of both close and distant objects. A punctiform object in nature is perceived as a line on the retina. One reason for this is usually related to the retina of the eye, which resembles an egg instead of a sphere in such cases. As a result of the different degree of curvature of the two meridians, light may be refracted more in the vertical plane than in the horizontal plane, for example. The result is a distorted image, e.g. a point may be distorted to a line.
Optical correction is achieved by correction of the curvature or by modelling the surface of the cornea into a spherical form so that all light rays converge at a focal point again.
With glasses and contact lenses, this is achieved by means of so-called cylindrical lenses, which must have a precisely defined direction in front of the eye. For this reason, the correction value for glasses or contact lenses is specified with the value of the cylinder in dioptres and the position of the cylinder axis in degrees. A “vision passport” would then have an entry for the cylinder value of -2.5 dpt, axis 75°, for example. In the case of an operation, the refractive power of the cornea is changed in order to achieve an optimum state.
Astigmatism often occurs in combination with myopia or hyperopia, and its correction value is also specified in dioptres.
Veni Vidi - octors of Ophthalmology
