What is Astigmatism? Clearing Up a Blurry Situation

Astigmatism is a very common condition. Approximately 1 in 3 people in the U.S. have astigmatism that affects the crispness and clarity of vision.

What is Astigmatism?

Simply speaking, it is an abnormally shaped curve in one or more structures of the eye that impacts its ability to focus. A good illustration is this: an eye without astigmatism is round like a basketball with symmetrical curves in all directions; an eye with astigmatism is shaped like a football, with two different curves. If the cornea or lens of the eye isn’t smooth and evenly curved, light can’t be sharply focused into the eye. As a result, vision is blurred.

Types of Astigmatism

Astigmatism is a blurry situation
Did you know LASIK can help correct astigmatism?

Because two structures of the eye can be impacted, there are two types of astigmatism:

  • Corneal astigmatism, the most common type, is the result of an irregularly curved cornea.  The cornea is the surface of the eye, the part you touch with your contact lens. It is where light first passes through as it makes its way into the eye.
  • Lenticular astigmatism is caused by a distortion in the crystalline lens. The lens sits behind the pupil in the eye to help focus light into the eye.  Light passes through the lens to the retina, the optic nerve, and, ultimately the brain.

Causes of Astigmatism

Most people are born with at least some degree of astigmatism, meaning it is hereditary.  However, sometimes it develops after an eye disease, injury, or surgery.

Can it Be Prevented?

For the most part, astigmatism can’t be prevented. It is simply an anatomical abnormality. Precautions against eye disease and injury, however, are generally recommended.

How is it Measured?

Astigmatism is measured in diopters (D), a unit of refractive or optical power. A perfect eye has 0 D. Most people have a mild prescription, between 0.5 to 0.75 D. They may not really notice it in their daily lives.  People with a measurement of more than .75 D may need contacts or eyeglasses to correct their vision to see clearly.  Here are a few measurements you may take away from your vision exam:

Sphere:  Measures your degree of nearsightedness (myopia) or farsightedness (hyperopia). A plus sign indicates you are farsighted.  A minus sign means you are nearsighted. The higher the number, the stronger your prescription.

Cylinder:  This is the severity of astigmatism or how irregular the cornea or lens is shaped. It is measured in diopters.

Axis: Locates the position of the irregularity on the cornea or the lens.  Axis is measured in degrees of an arc, like the curve of your eye, from 0 to 180.

Symptoms and Treatment Options

In addition to blurry vision, symptoms of astigmatism include eye strain and headaches. These are likely due to squinting and straining to try to see clearly. Importantly, blurred or distorted vision are symptoms of many conditions.  Schedule a visit to your eye doctor for a complete eye exam if you have new or worsening symptoms.  In addition to testing for and measuring any astigmatism, your eye doctor will evaluate your vision and eye health. Be sure to share any symptoms with your eye doctor as part of the complete evaluation of your vision.

Now that you know what astigmatism is, the next logical question is: What do I do about it?

It is a common misconception that astigmatism can only be treated with prescription glasses or contact lenses.  The good news is for those who don’t want to rely on glasses and contacts to see well, laser vision correction procedures can help.

Laser vision correction works by using precision laser technology to reshape the cornea to increase the eye’s focusing power. Today there are many options in laser vision correction that treat astigmatism, including LASIK, SMILE and PRK. 

Consequently, a thorough evaluation by a highly-qualified surgeon is the best way to determine what option is best to treat your astigmatism and other vision problems such as nearsightedness and farsightedness.

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