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Astigmatism

Astigmatism is a common eye condition that causes blurred vision due to either an irregular shaped cornea (the clear front cover of the eye), or the curvature of the lens inside the eye.

Overview

What is astigmatism?

Astigmatism is when part of the eye, either the cornea or the lens, is irregularly shaped. A perfectly curved cornea can bend, or “refract,” light properly as it enters the eye. In a person with astigmatism, either the cornea is egg-shaped with two different curves rather than perfectly round, or the lens has variations. Both irregularities cause images to reach the retina, the layer at the back of the eye, imperfectly. As a result, vision becomes blurred at any distance.

Most people have some degree of astigmatism. Slight amounts of irregularity usually don’t affect vision and don’t require treatment. However, larger amounts cause distorted or blurred vision, eye discomfort and headaches.

What are the different types of astigmatism?

There are three different types of astigmatism: myopic astigmatism, hyperopic astigmatism, and mixed astigmatism.

Myopic astigmatism

  • This happens when astigmatism is combined with near-sightedness and the two curves in the cornea (or lens) are focused in front of the retina.

Hyperopic astigmatism

  • This occurs when far-sightedness is combined with astigmatism and the two curves are focused behind the retina.

Mixed astigmatism

  • This happens when one curve is far-sighted and the other is near-sighted.

When to call the doctor

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Anytime you feel your vision is blurred or distorted or that your glasses/contact lenses are no longer giving you clear vision, you should make an appointment with your doctor.

Causes

What causes astigmatism?

The specific cause of astigmatism is unknown. It can be hereditary and is usually present from birth. It can change as a child grows and may decrease or worsen over time. Certain types of surgery or eye injuries that cause scarring of the cornea may also cause astigmatism. Astigmatism is not caused or made worse by reading in poor light, sitting too close to the television or squinting.

Symptoms

What are the symptoms of astigmatism?

Astigmatism symptoms come on slowly and may include:

  • Blurry or distorted vision
  • Excessive squinting
  • Eye strain
  • Headaches
  • Trouble sleeping

Diagnosis

How is astigmatism diagnosed?

A comprehensive optometric examination will include testing for astigmatism. Depending on the amount of astigmatism present, your optometrist can provide eyeglasses or contact lenses that correct the astigmatism by altering the way light enters your eyes.

A woman checks her eye at machine while a doctor stands beside her.

Treatment & Prevention

How is astigmatism treated?

Astigmatism is considered very treatable like other refractive conditions. Most people living with astigmatism lead normal lives and have no further eye issues.

Eyewear

Glasses can correct almost all cases of astigmatism. But if you have only a slight astigmatism and no other vision problems, you may not need them.

Contact Lenses

Astigmatism can also be corrected by either soft or rigid contact lenses.

Laser surgery

Another possible treatment option for some types of astigmatism, this surgery changes the shape of the cornea by removing a small amount of eye tissue. It is done using a highly focused laser beam on the surface of the eye.

Think you may have astigmatism?