What Is Astigmatism?

What Is Astigmatism and How Can It Be Treated?

Astigmatism is a vision condition that affects both near and distant vision. It occurs when the cornea — the clear, dome-shaped front surface of the eye — is shaped differently from one side to another. This irregular shape causes light entering your eye to focus incorrectly on your retina, resulting in blurred vision.

Astigmatism often occurs together with nearsightedness or farsightedness. As a result, it becomes difficult to see clearly at all distances. In the US, approximately 33% of people have astigmatism. This condition usually develops during childhood, but some people are born with it.

If you have astigmatism, you may notice that straight lines appear wavy or distorted when you look at them. Or perhaps your vision seems blurry no matter how hard you try to focus on objects close up or far away. Although astigmatism is not life-threatening, it can affect your eyesight and quality of life.

In this article, we'll look at astigmatism's causes and symptoms and ways to treat and manage it.
 

What Causes Astigmatism

The curvature of your cornea causes astigmatism. Generally, this cornea is shaped like a football (or oval) and helps focus light onto your retina, which sends images to your brain. If you have astigmatism, the shape of your cornea — the transparent covering over the iris and pupil — isn't round and smooth like it should be. Instead, it's more like a rugby ball or oblong shape with curves on both sides. This causes problems when light passes through your eye, as it can't focus properly. Instead of focusing on a single point on your retina, the light rays are scattered across multiple points and create blurry images.

Astigmatism is diagnosed when you have an eye exam as a child or teen. However, it can develop later in life, too. If you already have astigmatism and suddenly notice changes in your vision, contact your doctor immediately.

How Is Astigmatism Diagnosed?

You can get an eye exam to diagnose astigmatism. Your eye doctor will use an autorefractor tool to measure your refractive error and determine whether you have astigmatism. This device looks like a small TV screen that projects images of letters, numbers, and other objects onto your retina.

As you look at the images, your doctor will ask you to focus on them and tell them when they appear clear. As you do this, the autorefractor measures how much effort your eyes need to bring each image into focus. If astigmatism is present, both eyes will require different attempts to see clearly. It then uses this information to calculate whether you need glasses or contacts for clear vision.