Astigmatism

Astigmatism (uh-STIG-muh-tiz-um) is a common and generally treatable imperfection in the curvature of the eye that causes blurred distance and near vision.

Astigmatism occurs when either the front surface of the eye (cornea) or the lens inside the eye has mismatched curves. Instead of having one curve like a round ball, the surface is egg-shaped. This causes blurred vision at all distances.

Astigmatism is often present at birth and may occur in combination with nearsightedness or farsightedness. Often it's not pronounced enough to require corrective action. When it is, treatment options are corrective lenses or surgery.

How Does Astigmatism Affect Vision?

Normally, the cornea and lens at the front of the eye have an evenly round shape. This helps focus light rays sharply onto the retina so you can see clearly.

With astigmatism, light rays do not refract (or bend) properly as they enter the front of the eye. Vision is blurry at near and far because light rays either fall short of the retina or behind it.

People may have astigmatism along with other refractive errors, such as: nearsightedness (myopia) or farsightedness (hyperopia).