Like longsightedness and shortsightedness, astigmatism is another optical imperfection of the eye.
If you have perfect sight, then as light enters the eye, it is carefully focussed by various components of the eye to form a point on the retina.
Eyes without astigmatism have a round shape, resulting in a constant focusing effect over the cornea. In astigmatism, the front of the eye has an oval shape resulting in a variable focusing effect over the cornea.
Astigmatism can occur with myopia, hyperopia or alone. The higher the astigmatism, the greater the blur. Usually astigmatism causes blurring at all distances. Correction consists of refocusing the light on the retina.
There are several treatments options, however, the most common are glasses, contact lenses, and refractive surgery (LASIK, PRK).