What is Astigmatism?
Astigmatism is an eye problem that causes blurred vision at all distances. This common condition results from an irregular curvature of the parts of your eye that focus light (cornea and lens).
You can have astigmatism in one or both eyes, and it’s often present at birth. It may occur with other refractive errors, including:
- Myopia (nearsightedness). This is known as myopic astigmatism.
- Hyperopia (farsightedness). This is called hyperopic astigmatism.
Mixed astigmatism involves symptoms of myopia (blurred distance vision) and hyperopia (distorted up-close vision).
Types of Astigmatism
There are two types of astigmatism. It’s possible to have both types in one eye. The type of astigmatism you have depends on whether the cornea or lens is affected:4
- Corneal astigmatism. The surface of your eye (cornea) has an abnormal egg-shaped curve.
- Lenticular astigmatism. The eye lens is misshaped.
Regular vs. Irregular Astigmatism
Astigmatism can also be described as regular or irregular:
- Regular astigmatism. This type happens when the eye is evenly shaped like an oval or football.
- Irregular astigmatism. This type occurs when the eye’s curvature is uneven. Irregular astigmatism is less common than the regular type.
What Causes Astigmatism?
Astigmatism occurs when the cornea or lens has an irregular shape. The cornea and lens are structures that bend (refract) light onto your retina so you can see.
A perfectly shaped eye is round, like a smooth ball. With astigmatism, the eye’s curvature resembles an oval or egg shape. This prevents light from properly focusing on the retina, which leads to distorted vision.
Doctors don’t know why some people are born with astigmatism, and there’s no way to prevent it. They do know that certain factors make you more likely to have astigmatism.
Who is at Risk for Astigmatism?
Studies show these factors increase your risk for astigmatism:1,2
- Older age
- Eye injuries that cause corneal scarring or thinning
- Eye surgery, such as cataract surgery or LASIK
- Having a parent with astigmatism
- Family history of eye disorders, such as keratoconus
- Having a mother who smoked while pregnant
- Having other refractive errors (e.g., myopia and hyperopia)
Astigmatism affects 36.2% of Americans and is the most common refractive error in the U.S.3 It is not caused by squinting, reading in dim light, or watching the television up close.
Symptoms of Astigmatism
Some people with astigmatism do not experience symptoms. Those who do may experience the following:5
- Blurry vision when looking at near or far objects
- Straining or squinting to see objects more clearly
- Seeing glare or starbursts around lights
- Eye strain or discomfort
- Difficulty seeing at night
Astigmatism Symptoms in Children
Symptoms of astigmatism may be harder to detect in younger children. They may not notice they have a vision problem, so they won't be able to report it. This is why early childhood screenings for eye diseases and vision problems are so important.
If your child has frequent headaches or sudden changes in school performance, astigmatism may be the cause. Talk to your pediatrician, family physician, or other eye health professional if you suspect your child has a vision condition.
An eye doctor will need you to complete an eye exam. This includes reading a Snellen chart so they can assess your visual acuity.
They will also use tools to measure your vision, such as:
- Phoropter. A series of lenses that checks your prescription. It helps the eye doctor determine which lenses give you the clearest vision.
- Keratometer. The machine measures the steepest and flattest areas of your cornea. Doctors use it to determine how your eyes focus light.
- Autorefractor. The device shines light into your eye and then measures how it bounces off. It tells the eye doctor which lenses you need.
- Corneal topographer. The imaging test accurately measures your cornea and creates a detailed map. Surgeons use the image to create custom-fit lenses and plan your eye surgery.
Can Astigmatism Be Treated?
Yes. Regular astigmatism is a treatable condition. Eye doctors can accurately measure it and prescribe appropriate treatment.
Irregular astigmatism is not as easy to treat. Doctors are still finding ways to measure and correct it. As such, most treatments only correct regular astigmatism.6
Treatment options for astigmatism include:
Corrective lenses like glasses are commonly prescribed for astigmatism. When worn, they can focus light rays on your retina.
Eyeglasses that correct astigmatism are different from normal glasses. They have CYL (cylinder) and AXIS specifications, which denote lens power and the rotation of astigmatism correction.
If you have a combination of astigmatism and other refractive errors, your doctor may recommend progressive lenses.
Contacts are another standard treatment for astigmatism. Like eyeglasses, they bend light rays and focus them on your retina.
Doctors may prescribe disposable contacts, rigid contact lenses, or toric lenses designed for astigmatism.
You can choose contacts based on your budget and convenience. If you want to explore your options, check out our review of the Best Contacts for Astigmatism.
Laser Eye Surgery
Laser eye surgeries that correct astigmatism include:
- LASIK. Laser-assisted in situ keratomileusis (LASIK) treats astigmatism and other refractive errors. The surgical procedure involves cutting a small flap in your cornea and reshaping it with a laser. Not everyone is a candidate for LASIK.
- PRK. Photorefractive keratectomy (PRK) also reshapes your cornea with a laser. This procedure doesn’t involve a corneal flap, making it a better option for people with thin corneas.
- LASEK. Laser-assisted subepithelial keratectomy (LASEK) surgery is similar to LASIK and PRK. While PRK involves removing the outer surface of the cornea (epithelium), LASEK cuts a small flap in the epithelial tissue.
Orthokeratology is a non-invasive lens correction therapy. It is often used to treat myopia. But it can also correct mild-to-moderate astigmatism.
The treatment lasts two weeks and involves wearing rigid gas-permeable contact lenses. These lenses are designed to fit your eyes and gently reshape your cornea.
Once the cornea adjusts to a normal shape, the ophthalmologist will provide retainer lenses to help maintain it.
Lens Replacement Surgery
Also known as refractive lens exchange, it is an invasive surgical procedure that removes the misshaped eye lens. The surgeon replaces the natural lens with a toric lens.
Lens replacement is recommended for:
- Lenticular astigmatism
- People at risk or already have cataracts
Phakic Intraocular Lenses (IOLs)
The treatment is an invasive surgery that inserts phakic lenses into your eye. But instead of replacing your eye's natural lens, it is either placed at the front or behind it.
Phakic lenses treat severe myopia and myopic astigmatism.
Frequently Asked Questions
How can you tell if you have astigmatism?
Blurred vision at various distances is a classic sign of astigmatism. However, it is best to consult an eye doctor. They can diagnose astigmatism using tools and tests that assess your eye health and how your cornea refracts light.
How is astigmatism measured?
Eye doctors use a keratometer to measure astigmatism in diopters (D).
Mild astigmatism is 0.10 to 1.00 D
Moderate astigmatism is 1.00 to 2.00 D
Severe astigmatism is 2.00 to 4.00 D
Extreme astigmatism is over 4.00 D
Can astigmatism go away?
No. Astigmatism does not go away on its own. That said, most available treatments can correct astigmatism. Some treatments provide more permanent solutions.
Does astigmatism get worse with age?
It depends. Astigmatism can stay the same or worsen, depending on your eye health. Studies show that it can worsen with age. It tends to be stable until the age of 50. By the time a person reaches 60 years old, it progresses.7
What degree of astigmatism requires glasses?
Moderate to extreme astigmatism that measures 1.50 to 4.00 diopters can be corrected with glasses. However, an eye doctor can help determine if eyeglasses are your best option or if you should consider other treatments.
What are the best glasses for astigmatism?
Trivex, polycarbonate, and high-index lenses are best for severe cases of astigmatism.
Do I need specific contacts for astigmatism?
Yes. Disposable and rigid gas-permeable lenses with a cylindrical (toric) design are recommended. They can correct astigmatism and other refractive errors.
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