Astigmatism
Astigmatism is a common type of refractive error. It means that some part of your eye (either the cornea or lens) is more curved than it should be. This altered eye shape makes your vision blurry. Most cases of astigmatism can be treated with corrective lenses like eyeglasses or contact lenses.
What is astigmatism?
Astigmatism is the medical term that means the shape of your eye is more curved than it should be. It’s a type of refractive error — an extremely common eye condition that causes blurred vision.
Usually, eyes are round, like a baseball. If you have astigmatism, your eye is shaped like a football or the back of a spoon. This makes light that enters your eyes bend unevenly and affects your vision at all distances.
Visit an eye care specialist as soon as you notice any changes in your eyes or feel like your vision isn’t as clear as it used to be.
What does astigmatism do to your vision?
The parts of your eyes work together like a relay team to pass light that enters your eye along a pathway to your brain. Light passes through your cornea — the clear part at the front of your eye. Your cornea focuses that light through your lens into a signal that hits your retina — the layer at the very back of your eyeball. Your retina converts that light into electrical signals that your optic nerve sends to your brain. Your brain then uses those signals to create the images you see.
If you have astigmatism, light that enters your eye is bent more than it should be. The light can’t properly focus on your retina. This means only parts of an object you’re looking at are in focus. That uneven focus makes objects look blurry or wavy. Astigmatism can affect your vision at any distance — both up close and farther away.
You might experience eye strain — like your eyes are constantly working too hard to see.
What are the types of astigmatism?
Astigmatism is usually caused by your cornea having an irregular shape. Eye care specialists call this corneal astigmatism.
You can also have lenticular astigmatism, where the lens in your eye has an irregular shape. Lenticular astigmatism is often caused by cataracts.
Some people have both corneal and lenticular astigmatism.
Who is affected by astigmatism?
Anyone can experience astigmatism. You can develop it at any point in your life. Some people are born with astigmatism. Others don’t develop it until they’re adults. It can get better or worse over time.
Astigmatism is very common. 1 in 3 people has astigmatism.
What causes astigmatism?
Astigmatism is usually hereditary, which means it’s a condition biological parents pass down to their children. It can also be caused by your eyelids putting too much pressure on your cornea.
Astigmatism usually isn’t caused by health conditions. Some conditions and issues that can cause astigmatism include:
- Eye injuries.
- Keratoconus.
- Complications after eye surgery.
What are astigmatism symptoms?
Blurred vision is the most common astigmatism symptom. It also makes it hard to see details on objects, like the words printed on a menu in front of you, or letters on a road sign in the distance.
Other astigmatism symptoms include:
- Seeing a glare or halos around lights.
- Squinting to see clearly.
- Headaches.
- Fatigue.
- Eye strain.
Some young children don’t know there’s anything wrong with their vision, even if they’re experiencing symptoms. Visit an eye care specialist if you notice your child squinting, rubbing their eyes or having frequent headaches.
How is astigmatism diagnosed?
An eye care specialist will diagnose astigmatism with an eye exam. They’ll look at your eyes (including inside them).
Your eye care specialist might use a few tests to diagnose astigmatism, including:
- Visual acuity test: A visual acuity test is a test that checks your vision. You’ve had a visual acuity test if you’ve ever looked at a wall chart of letters or symbols during an eye exam.
- Refraction test: Your eye care specialist will measure how much light focuses and is bent as it enters your eye.
- Keratometry: Keratometry measures your cornea’s curve.
- Slit lamp exam: A slit lamp is a special microscope with a bright light that your eye care specialist shines into your eye. They’ll adjust the brightness and thickness of the light’s beam to see the different layers and parts of your eye.
How is astigmatism treated?
Most people with astigmatism need corrective lenses. Your eye care specialist will recommend eyeglasses or contact lenses to help you see clearly.
If the astigmatism is very mild (and doesn’t affect your vision), you might not need glasses or contacts. Your eye care specialist will measure any changes in your eye during future eye exams. Astigmatism can change over time and get worse, so you might need glasses or contacts eventually, even if you don’t at first.
Can astigmatism be corrected?
Wearing glasses or contacts will correct your vision, but they won’t change the shape of your eye. Vision correction surgery (including LASIK eye surgery and photorefractive keratectomy or PRK eye surgery) uses lasers to fix vision problems. A specially trained ophthalmologist will perform these procedures to change the shape of your cornea so light hits your retina correctly.
People who have cataracts and astigmatism can have both treated at the same time during cataract surgery.
These surgeries will reduce astigmatism and improve your vision. Talk to your eye care specialist if you’re interested in vision correction surgery.
What can I expect if I have astigmatism?
If you have a small degree of astigmatism that doesn’t affect your vision, you might not need any treatment. If you have a significant astigmatism that makes it hard to see clearly, there are lots of ways your eye care specialist can treat it. Many people with astigmatism only need glasses or contact lenses.
Most people who have vision correction surgery have permanently improved vision. Some people need an enhancement procedure as they get older. This follow-up procedure will correct any changes in the astigmatism that happen after your eyes naturally change shape as you age.
How can I prevent astigmatism?
You can’t prevent astigmatism. Most people who have astigmatism are born with it. Others develop it as their eyes grow and change throughout their lives.
If you have astigmatism or another type of refractive error, there’s a chance your children might as well.
When should I have my eyes examined?
Having your eyes and vision checked regularly can help an eye care specialist identify problems right away. How often you should get your eyes checked usually depends on your age.
- Kids: A pediatrician should check your child’s eyes at every well-child visit until they’re old enough to start school, and then every one to two years.
- Adults younger than 40: Every five to 10 years.
- Adults between 40 and 54: Every two to four years.
- Adults older than 55: Every one to three years.
You might need your eyes checked more often than this if you wear glasses, contacts or need another type of visual aid. People with diabetes also need their eyes checked more often than what’s listed here.
Ask an eye care specialist how often you need an eye exam.
When should I see an eye care specialist?
Visit an eye care specialist as soon as you notice any changes in your eyes — especially if your vision is getting noticeably worse or blurry. Astigmatism symptoms are usually very noticeable at night, when it’s raining or when you look at lights.
What questions should I ask my eye care specialist?
- Which type of astigmatism do I have?
- Will I need corrective lenses?
- Are glasses or contacts better for my eyes?
- Am I a good candidate for vision correction surgery?
- How often should I have my eyes examined?
References
- American Optometric Association. Astigmatism (https://www.aoa.org/healthy-eyes/eye-and-vision-conditions/astigmatism?sso=y). Accessed 11/20/2022.
- Gurnani B, Kaur K. Astigmatism (https://pubmed.ncbi.nlm.nih.gov/35881747/). 2022 Jul 2. In: StatPearls [Internet]. Treasure Island, FL: StatPearls Publishing; 2022 Jan-. Accessed 11/20/2022.
- National Eye Institute. Astigmatism (https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/astigmatism). Accessed 11/20/2022.
- National Library of Medicine. Astigmatism (https://medlineplus.gov/ency/article/001015.htm). Accessed 11/20/2022.
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