Your eyes are some of the most hardworking parts of your body. From the moment you wake up until you fall asleep, they’re processing millions of bits of information to show you the world around you. All this hard work means that eye issues are common, so it’s important to be aware of any problems with your vision.
One of the most common eye issues is astigmatism, which affects one in three people. If you’ve got blurry vision or have trouble seeing at night, you might have astigmatism.
The good news is astigmatism can be treated pretty easily with the help of an eye care specialist. Let’s look at the symptoms of astigmatism, what causes it and what treatments are available.
There are two main types of astigmatism: corneal and lenticular. Both types cause refractive errors and some people can have both kinds of astigmatism.
Corneal astigmatism
Corneal astigmatism means that the shape of an eye’s cornea – which is the clear front layer of your eye – isn’t the same all the way around like a sphere is.
If a cornea does not have astigmatism, light entering the eye bends evenly and hits the retina at one focal point. The retina is the layer at the back of the eye that converts light into electric signals that your optic nerve sends to your brain. When the cornea has an irregular shape, it causes light to refract, or bend, unevenly. The light hits more than one focal point on the retina, causing you to see images and objects as blurry and out of focus.
Lenticular astigmatism
Lenticular astigmatism means the eye’s lens is shaped differently. The lens sits behind the iris, which is the colored part of the eye.
The same issues can affect the eye’s lens, the inner part of the eye that helps you focus. Squinting helps correct refractive errors to one focal point, which is why it’s important to get your eyes checked if you find yourself squinting to see things clearly.
Symptoms of astigmatism
If you have a mild astigmatism, you might not notice any symptoms. But the most common astigmatism symptoms are:
- Blurry vision
- Difficulty seeing at night
- You may see halos or glares around lights at night, which can make driving harder.
- Headaches
- Eyestrain, squinting or the urge to rub your eyes
- Astigmatic vision can make your eyes feel like they’re working extra hard. You may have to squint to see things clearly, and this strain on your eyes may cause headaches, tiredness and the urge to rub your eyes.
- Lazy eye (amblyopia) in children
- This means one eye doesn’t see as well as the other.
Kids often don’t notice vision issues, so it’s a good idea to get their eyes examined when they’re babies, toddlers, before they start school and yearly as they grow up. It’s important for adults to have regular eye exams as well.
Causes of astigmatism
Many different factors can cause astigmatism, though doctors and scientists don’t know all the causes. Some people are born with it, and some develop it in childhood or adulthood. It’s important to know that you can’t give yourself an astigmatism by reading in low light or watching TV or screens too closely. These activities can irritate your eyes and make it hard to focus, but they won’t cause you to develop an astigmatism.
Genetics
Many people with astigmatism are born with it because it can be passed down from parent to child through genetics. If you have a close family history of astigmatism, it’s a good idea to get your eyes checked.
Eye injuries
Injuries from contact sports, chemicals, fireworks and accidents can all cause eye trauma that can lead to astigmatism. Damage to the cornea can also happen when you get something irritating stuck in your eye, or if you rub your eyes too hard. This can create corneal scars and cause your cornea to weaken.
Surgery complications
Like with any surgery, there’s a small risk of complications with eye surgery, though they’re rare. Some surgical complications can cause changes to the curve of the eye or affect your glasses prescription in other ways.
Keratoconus
This condition happens when the cornea is weak, so it bulges and takes on a cone shape. The cornea is thinner in some areas, which leads to distorted vision. Keratoconus is often treated with prescription hard contact lenses that help shape the cornea.
Cataracts
Cataracts are normal changes to the lens of the eye and are caused by proteins breaking down over time. They’re a normal part of aging. As they develop, the eye’s lens changes, and this can cause astigmatism.
Eye conditions that can occur alongside astigmatism
Astigmatism can happen when you have other refractive errors of the eye. These refractive errors are myopia, hyperopia and presbyopia.
Myopia (nearsightedness)
Myopia is a refractive error that occurs when light entering the eye focuses in front of the retina, possibly because the cornea is curved too much or because the eye is longer than an average eye. This causes nearsightedness, meaning that far objects and images are blurry.
Myopia is a common eye issue that affects approximately 40% of the U.S. population. Because about 75% of people with myopia get diagnosed between the ages of 3 and 12, it’s a good idea to monitor your child’s vision and talk to their pediatrician if you think they might be having vision issues.
Hyperopia (farsightedness)
Hyperopia is the opposite of myopia. In hyperopia, the cornea’s curve may be too flat, or the eye may be shorter than average. This causes the light that enters the eye to focus behind the retina. This is known as farsightedness, meaning that while you can see objects and images that are far away more clearly, near ones appear blurry.
Presbyopia
Presbyopia is a condition that naturally occurs as you age. It usually shows up during your 40s and means that the lens in your eye is gradually less able to change shape to focus. Presbyopia can usually be corrected with glasses.
If you think you might have astigmatism, it’s a good idea to see an eye care specialist. It’s especially important to do this if the symptoms of astigmatism are interfering with your daily activities such as reading or driving. Your eye care specialist will perform a series of diagnostic tests.
Astigmatism tests
Eye care specialists can perform several different tests to tell if you have astigmatism. These tests cover all areas of your vision and will help your doctor determine exactly what your vision issues are. None of these tests hurt – you might just feel a mild discomfort with some of them.
During your exam, your doctor will likely dilate your eyes with eye drops that cause the pupils to widen, giving them an opportunity to look inside more easily. You might feel a bit of discomfort when the drops are put in, however it will only last a few seconds. Also, as your eyes dilate, you’ll become more sensitive to bright light, and your vision will get blurrier. These effects last about four hours, so you will need sunglasses and will have blurred vision for several hours.
Visual acuity test
This test is done with an eye chart, and you’ll test each eye separately. Your eye doctor will have you read several rows of letters or shapes. Each row is smaller than the one before it, and you’ll identify them until you can no longer tell what they are. This helps your specialist determine how your eyes can understand detailed shapes from a distance. This is called your visual acuity.
Typical visual acuity is 20/20, which means you need to be 20 feet away from an object or image that most people can also see from 20 feet away. If your visual acuity is 20/40, that means you need to be 20 feet away from an object or image that most others can see from 40 feet away.
Refraction assessment
This test can have a few parts. One is a retinoscopy, where your doctor shines a light into each eye to see how light is reflected in your retina. This helps them identify any refractive error. A machine that is sometimes used at the start of the exam is called an autorefractor, which also obtains measurements related to the glasses prescription and the curve of the cornea.
Refraction is the next part of the exam, using a phoropter, a machine that looks like an eye mask and has many little lenses inside. Your doctor inserts lenses for you to look through, determining which lens allows you to see letters or objects on a chart more clearly. They may repeat this several times to see which lens gives you the clearest vision.
Keratometer and topography scan
Some patients with astigmatism will need evaluation with a keratometer or topographer. A keratometer measures the curvature of your cornea. You’ll sit with your chin on a chinrest while the machine projects light onto a curved mirror, which is reflected off the cornea. This allows your doctor to measure exactly how your cornea is curved.
A topographer is a machine that scans the cornea and shows imperfections or irregularities on its surface. These scans can be compared over time to monitor different conditions with astigmatism.
Astigmatism treatments
Can astigmatism be corrected? Yes! Astigmatism doesn’t go away on its own, so treatments are the best way to improve it. There are two main types of astigmatism treatment – corrective lenses and surgery.
Glasses and lenses
Corrective lenses are used to adjust the refractive errors caused by astigmatism. They’re generally more affordable and less permanent than having surgery.
The least expensive corrective lens option is a pair of glasses. Eyeglasses can be fitted with corrective lenses made to your specific prescription. They help the light that enters your eyes refract properly onto the retina, getting as close to that single point of focus as possible.
Contacts are another choice. These are lenses that go right onto the eye to help correct the light refraction. They’re available in hard and soft options. Hard lenses are rigid, and manually change the shape of the cornea, fitting the cornea into a rounded shape. A version of soft lenses called toric lenses are also helpful in treating astigmatism’s refractive errors.
Surgeries for astigmatism
Some people with astigmatism may be able to consider refractive eye surgery if their vision corrects well with lenses and is stable.
LASIK and photorefractive keratectomy (PRK)
Eye surgeries that people consider include LASIK surgery and PRK, which is similar to LASIK. These procedures use lasers to adjust the shape of the cornea.
Cataract surgery
If people have cataracts and have astigmatism, and the cataracts have gotten significant enough to need cataract surgery, there are premium cataract surgery options to consider. These surgery options could lessen the dependence on glasses due to astigmatism.
If you think you may have astigmatism, scheduling a routine eye exam is a good place to start. Your care provider will consider your symptoms and test your eyes to figure out any vision issues.