Astigmatism values

Regular and irregular astigmatism

If the cornea in their Meridians is unphysiologically curved, image distortions occur.
Regular astigmatism (corneal curvature) is an ametropia that is defined by such an altered corneal curvature.
The normal-sighted eye has a cornea that is not spherically curved, but certain, precisely coordinated curvatures in the vertical and horizontal directions.

These curves are essential in order to be able to refract the light that comes in from the side, from below or from above, as well as the light that comes in from the front.
However, if the cornea is in one of the directions (meridian) is changed compared to the physiologically correct curvature and is therefore bent more or less, the light that passes through the pupil is refracted differently and then also differently resolved in the individual meridians.
An actually round object, like a sphere, appears like a line or a rod (Astuteness).

Irregular corneal curvature

Irregularities on the corneal surface are called irregular astigmatism. With this form of astigmatism, an irregular curvature in the cornea leads to a lack of focus.
The cause of the irregularity of the cornea can, for example, be a corneal disease with scarring.
This not only changes the axes, but also shifts them against each other.

Correction of astigmatism

For regular astigmatism, the correction is made with the help of cylindrically cut glasses by.
These so-called Cylinder glasses the light only refracts in one direction, which is why an axis direction is always given in degrees when prescribing the corresponding glasses.
The concave and convex Cylinders are ground in such a way that the two axes are perpendicular to each other and only their refractive power is changed.

Initial adjustment

The first adjustment of cylinder glasses in adulthood is often problematic because the long period of getting used to seeing without compensation has resulted in an adjustment of the processing of the images seen.
The sudden change to normal vision through the strong glasses results in sharper vision, but at the same time often leads to headaches.
For this reason, adolescents and adults who need glasses with cylinder lenses for the first time usually start with a weaker lens than would be required according to the measurement. Then the strength is gradually adjusted.

Permanent correction through lasers

A treatment with the so-called Excimer laser enables a direct correction to the eye, whereby the refractive power is changed in such a way that sharp vision is possible without any aids.
The zone of increased refraction is then ablated with the help of the cold light laser if the cornea is curved. This laser penetrates the cornea only a little, making it possible to gently change the cornea without damaging adjacent tissue.
However, due to the individual characteristics of the cornea, such as corneal thickness, not everyone can be treated with laser therapy.

For more information, see: Laser therapy for astigmatism