Astigmatism is an uneven curvature of the eye’s cornea or lens. It’s a very common eye condition—about one in three Americans have it. Although it can cause inconvenient vision problems, including blurry vision and poor eyesight at night, it’s typically very treatable. Often, all you need is a new pair of glasses or contact lenses.
Think of your cornea as a clear, rounded dome over the surface of your eye. In people with astigmatism, that dome isn’t perfectly rounded—it’s shaped more like an egg or a football. The irregular shape of the cornea affects how light is focused inside the eye. An evenly round cornea (without astigmatism, as seen below) focuses light rays into a single point on the retina at the back of the eye, producing a clear image. But an unevenly shaped cornea can’t focus light with the same precision. It bends the light, so it hits multiple points on the retina instead of just one, resulting in blurred vision at all distances.