Astigmatism is a common vision disorder, but is not an eye disease. It’s a refractive error that occurs when your cornea (the surface of your eye) has an asymmetrical shape. Astigmatism is like nearsightedness and farsightedness; it can be corrected with prescription eyeglasses, astigmatism correction contact lenses or laser eye surgery.
A good analogy to describe the irregular shape of your eye in astigmatism is to think of sports: your cornea is shaped like a football instead of round like a baseball. Astigmatisms can also be slightly oblong like an egg. With astigmatism, your medians are misaligned. Think of meridians like a clock’s face. A line linking the 12 and 6 is one meridian, and a line from the 3 to the 9 is another meridian. The flattest and steepest meridians are principal meridians.
Astigmatism typically causes blurred or distorted vision. Common symptoms of uncorrected astigmatism are headaches and eye strain, usually after reading or other prolonged tasks of intense focus. Another common symptom is squinting.
Astigmatism is classified as regular or irregular. A regular astigmatism has principal meridians that are 90 degrees apart and are perpendicular to one another. An irregular astigmatism occurs when the principal meridians are not perpendicular. Irregular astigmatism may result from an eye injury, keratoconus or from eye surgery. Most astigmatisms are regular.