Astigmatism: Causes, Types, and Symptoms

Astigmatism is a common eye condition that causes blurred vision. Many people have some degree of astigmatism.

In this condition, some part of your eye — usually the cornea has an irregular curve. The cornea is the outer layer of the eye. It helps your eye focus light so you can see.

Astigmatism

What happens to the eye in astigmatism?

Our eyes have a spherical, or round, shape. When light enters the eye, it refracts evenly. Refraction mean light changes direction when it enters your eye at an angle. When light refracts evenly, it focuses precisely on the retina at the back of your eye. You see objects clearly.

If you have astigmatism, your eye’s shape is like a football or the back of a spoon. When light enters the eye, it refracts unevenly — more in one direction than the other. The light can’t properly focus on the retina. When that happens, only one part of the object is in focus at a time. At any distance, things look blurry and wavy. Some people with astigmatism experience eyestrain rather than blur, while others experience both.

The curvature can change, so astigmatism can increase and decrease over time.

What other conditions may occur with astigmatism?

Astigmatism is one of several conditions known as refractive errors, which affect how our eyes refract or bend the light. Other refractive errors include:

Myopia (nearsightedness).
Hyperopia (farsightedness).
Presbyopia (difficulty focusing at near).

Who is at risk for astigmatism?

Factors that may put you at higher risk for astigmatism include:

Hispanic or Black ethnicity.
Being nearsighted or farsighted.
Having a mother who smoked during pregnancy.

How common is astigmatism?

Astigmatism is a common eye condition. About one in three people has some degree of astigmatism. It happens along with nearsightedness or farsightedness.

What are the types of astigmatism?

Corneal astigmatism is the main type. The cornea is egg-shaped instead of round.

Lenticular astigmatism affects the lens, not the cornea. The lens has imperfections that prevent images from reaching the retina clearly. People with this type of astigmatism often have a normal-shaped cornea, though it is possible to have both.

Is astigmatism the same as lazy eye?

These two eye conditions are not the same, but they can go together. Lazy eye, or amblyopia, is a different eye condition where vision in one eye is weaker than in the other. Unbalanced astigmatism — a difference between the two eyes — can cause lazy eye. In childhood, the brain develops a preference for the eye that provides a better image and neglects the other eye, causing vision to get worse in a sometimes permanent way. Unfortunately, lazy eye can occur without patients or their parents noticing. Amblyopia is treatable if caught early, so children should be checked often for vision problems — at least annually.

What causes astigmatism?

Astigmatism is often hereditary, which means it’s passed down from your parents. It can also be the result of eyelids putting pressure on the cornea. It can get better or worse over time.

Sometimes, astigmatism happens after an eye injury or surgery. Another cause is a condition called keratoconus. In this condition, the cornea becomes thinner and more cone-shaped over time. You end up with severe astigmatism. Some people with keratoconus need a corneal transplant.

What are the symptoms of astigmatism?

If you have astigmatism, you may have:

Headaches.
Fatigue.
Eye strain.
Blurred vision (at all distances).
Squinting to see clearly.

These symptoms are also symptoms of several other conditions. An eye specialist can help diagnose the problem.

It can be tricky to diagnose astigmatism in children. It often goes undetected, because children may not complain about blurred vision. If your child mentions ongoing headaches or eye troubles, talk to your child’s healthcare provider.

How is astigmatism diagnosed?

An optometrist or ophthalmologist performs a complete eye exam to diagnose the problem.

What tests might I need?

Various tests measure how your eyes focus light and what type of lenses you need to improve your vision. Astigmatism tests include:

Visual acuity: You read letters on a distance chart and receive a measurement (for example, 20/20 or 20/40). Alternative methods are used for young children and non-verbal patients.
Keratometry/topography: This instrument measures the curve of your cornea. Your provider focuses light on the cornea and measures its reflection. This number is important for getting contact lenses that fit correctly and diagnosing regular versus disease-induced astigmatism.
Refraction: Your provider measures how light focuses within your eye to create a clear or blurry image. This can be done with or without your input, so it can still be done in children and non-verbal adults.

How is visual acuity measured?

“Having 20/20 vision” means perfect vision. The top number is the standardized testing distance used, which is 20 feet. The bottom number represents the smallest letter size you can read. So if you have 20/40 vision, it means you need to be within 20 feet to read a letter that someone with perfect vision could see clearly at 40 feet.

What’s the difference between an optometrist and ophthalmologist?

Both are eye care specialists, trained in caring for eyes:

Optometrists prescribe glasses and contact lenses, and provide care for routine and some medical eye conditions. Some optometrists specialize in a particular area, like pediatrics or difficult to fit contact lenses.
Ophthalmologists provide total eye care and often specialize in particular aspects of medical eye care such as glaucoma or retinal conditions. They can diagnose and treat eye conditions using medication, surgery and other procedures.

Optometrists and ophthalmologists coordinate together to meet all the eye care needs of their patients.

How is astigmatism treated?

The main treatment for astigmatism of all degrees is corrective lenses, either eyeglasses or contact lenses. If you have very slight astigmatism and no other conditions (such as nearsightedness or farsightedness), you may not need glasses. If you have moderate or high astigmatism, you will likely need corrective lenses.

Other treatment options include:

Orthokeratology (ortho-k): You wear a series of specially designed contact lenses. The lenses are rigid, so they reshape the curve of your cornea over time.
Laser surgery: Laser in-situ keratomileusis, or LASIK surgery, can correct some types of astigmatism. Talk to your healthcare provider to see if it’s right for you. The surgeon uses a laser to remove a small amount of eye tissue and change the shape of the cornea.
Photorefractive keratectomy (PRK): PRK eye surgery removes tissue from the cornea’s inner and outer layers.

Are eyeglasses or contact lenses better for astigmatism?

People with astigmatism sometimes prefer eyeglasses to contact lenses. The eyeglasses have a special lens that helps compensate for the astigmatism.

Other people prefer contact lenses for astigmatism because they give you a wider field of vision. Your healthcare provider will help figure out the best contact lenses for you.

What are toric lenses?

If you have moderate or high astigmatism, you may need special corrective lenses called toric lenses. These lenses bend light more in one direction than the other. Your eye doctor will use various eye tests to figure out the right toric lens prescription for you.

Who can have surgery for astigmatism?

If you have generally healthy eyes, you may be a candidate for astigmatism surgery. Your healthcare provider will discuss the types of refractive surgery and recommend the best one for your needs. The two surgical options are LASIK surgery and PRK eye surgery.

How does ortho-k work?

These special, rigid contact lenses help reset your cornea. You wear them for a set period, such as overnight, and then remove them. If you have moderate astigmatism, wearing these lenses just at night may help you get clear vision during the day. However, ortho-k is not a permanent fix. If you stop wearing the retainer lenses, your vision will likely return to how it was before. While there are lifestyle benefits, there is also a higher risk of infection associated with wearing contact lenses at night.

Can astigmatism be cured?

Laser surgery can provide a long-term solution for astigmatism. Depending on the severity, you may need more than one procedure.

How can I prevent astigmatism?

Regular eye exams are important for your vision and health. Astigmatism may increase slowly. A yearly eye exam with an optometrist or ophthalmologist helps keep tabs on any vision problems.

Will astigmatism go away?

Laser surgery can correct some types of astigmatism. Other treatments improve your vision but won’t cure astigmatism.

What is the outlook for people with astigmatism?

Glasses or contact lenses help you have clear vision. Laser surgery can offer a permanent fix. See an eye care professional regularly — especially children. This provider can adjust your vision prescription as necessary.

How do I take care of astigmatism?

Talk to your healthcare provider if you notice any vision changes. Keep all recommended eye appointments to help manage astigmatism and change your treatment if necessary.