The causes of astigmatism are well known. Normally, light rays pass through the cornea and the lens to focus on the retina. In case of astigmatism, there is a problem on a radius of curvature of the cornea or lens, or both.
The cause is a refractive power of the eye that is different on a meridian. This is a problem that concerns a radius of curvature. The problem may be with the cornea which has no more perfectly harmonious bend radii. We talk about corneal astigmatism.
There does not seem to be any hereditary causes for this astigmatism, we have compared child populations, some of which have astigmatic parents. It does not seem that there are differences according to heredity.
Among the causes of astigmatism, this defect of vision may be due to particular diseases (keratoconus, pterygium), but also appear as a result of corneal trauma with the formation of a scar that modifies the corneal curvature, or following a surgical procedure whose suture requires tight spots resulting in deformation of the cornea.
The cause of astigmatism may also be related to a deformation of a radius of curvature of the lens. Sometimes the problem affects both the cornea and the lens.
Astigmatism is not caused by intensive reading of books or screens ...