Astigmatism is a distorted vision, caused by uneven curvature of the cornea. The eye sharpens the vertical, not the horizontal lines, or vice versa, which depends on which light beams bend due to improper curvature. The diagonal lines may also be out of focus.
Astigmatism usually occurs along with short-sightedness or long-sightedness. It is usually innate and does not get worse with age.
What to do?
If you suspect you do not see well, go to the ophthalmologist. If the examination shows that you have astigmatism, the ophthalmologist will prescribe the spectacles with curved shapes (lenses) that are needed to correct the corneal inequality. Such lenses are called cylindrical.