Astigmatism Overview

What is Astigmatism?

Astigmatism is a fairly common condition characterized by a mild and generally easily treatable imperfection in the curvature of the eye. The condition can cause blurred vision and difficulty focusing.

Astigmatism occurs when the front surface of the eye or the lens inside the eye has a slightly different surface curvature in one direction from the other. Instead of being even and smooth in all directions, the surface may have some areas that are flatter or steeper.

Astigmatism blurs the eye's vision at all distances. Astigmatism is often present at birth and may occur in combination with nearsightedness or farsightedness. Often it is not severe enough to require corrective action. When sever cases are present in individuals, treatment options include corrective lenses and surgery.

Most of the focusing power in the eye occurs along the front surface, at the cornea, or within the lens, which sits behind the cornea inside the eye. The ideal cornea or lens has a symmetrically curved surface, like a basketball. Astigmatism is caused by a cornea or a lens that is oblong rather than symmetrically sphere, similar to a football.

The cornea is the transparent portion of the eye in front of the colored iris. It redirects light rays to focus images onto the retina in the back of the eye. When the cornea is oblong rather than circular, it is not possible for the light rays to be focused at a single point. As a result, individuals who have significant astigmatism may have distorted or blurry vision.

Astigmatism can run in families and often occurs in combination with other refractive problems such as nearsightedness or farsightedness. Astigmatism is measured in units known as diopters. A measure of greater than 1 diopter typically requires correction with glasses or soft contact lenses.

Last Updated: September 06, 2016