Astigmatism occurs when the cornea, or the eye lens, has an irregular curvature, and it is one of a group of eye conditions known as refractive errors.
There are two kinds of astigmatism; regular and irregular. Regular astigmatism is an alteration in the normal shape of the cornea, or lens. Irregular astigmatism is is caused by a corneal scar or scattering in the crystalline lens.
Astigmatism can be corrected with eyeglasses, contact lenses, or refractive surgery.