What is Astigmatism?

Astigmatism is a common cause of blurry vision. In contrast to nearsightedness (AKA myopia), which blurs your distance vision only, astigmatism will blur both your distance and near vision. If your eye doctor tells you that you have this form of refractive error, then you will see better with glasses or special toric contacts that are made for astigmatic eyes. Glasses and toric contacts do not get rid of astigmatism. These strategies focus the light, allowing you to see well despite having astigmatism.  But what is astigmatism?

What is astigmatism, and how does it differ from myopia and hyperopia?

What is astigmatism, and how does it differ from myopia and hyperopia?


If you have no astigmatism, then the cornea is perfectly round, like a marble. People who have an astigmatic have a cornea that is warped to some degree, kind of like an egg. As a result, these patients have different powers in different parts of their eye, so their optometrist or ophthalmologist will prescribe lenses that have different powers in different parts of the lens to focus the light.

Most people’s astigmatism is a natural result of the forces placed on their eye by their eyelids and the bones of the face. It can, however, be a result of eye injury or pterygium (which is advanced sun damage to the front of the eye), or in some cases, astigmatism can even result from aggressive eye rubbing. If your astigmatism has been going up over the years, your eye doctor may ask you about eye allergies or a habit of eye rubbing. If your eyes are uncomfortable for any reason and you tend to rub them often, see your optometrist about treating the discomfort.

Rubbing the eyes hard enough to make them go “out of round” can damage and warp them over time. If you think about it, the eyes are a rather delicate structure; there are no bones holding them together. Over a period of years aggressive eye rubbing can even lead to a terrible eye disease called keratoconus. If you rub your eyes out of habit, try to stop. If you rub them because they itch, go see your local eye doctor for a medical office visit to resolve the itch. Some astigmatic patients may even be eligible for Lasik or PRK surgery to correct their astigmatism if their eyes are otherwise healthy and they have had a stable glasses prescription. Most patients with astigmatism can achieve 20/20 vision (or close to it) with the proper glasses or contacts.

Sincerely, Dr. Mark Cannon, optometrist @ Cannon EyeCare (at Market Optical) in Seattle, Washington