Astigmatism and Vision Correction: What to Know

Medically reviewed by Bryan M. Wolynski, OD

If you have astigmatism, your vision may be blurry and distorted instead of sharp and crisp. In astigmatism, the cornea (the clear dome that covers your eye) or the lens (which focuses light rays on the light-sensitive retina) is abnormally shaped.

Wearing contact lenses or glasses that refocus light rays where they should be can enable you to see as clearly as possible. An eye specialist, usually an ophthalmologist or optometrist, will examine your eye, assess your vision, and take the necessary measurements for corrective lenses.

This article covers astigmatism affects what you see, what happens if it worsens, what symptoms to watch for, why you may develop it, and more.

Astigmatism: What Do People See

With astigmatism, many things appear out of focus. While many people have this condition to some degree, it can affect some more severely than others.

Living with astigmatism can be confounding, with blurry vision at both near and far distances. In some cases, straight lines may appear wavy or distorted. Also, lights at night may streak out from the source, with annoying streamers appearing around oncoming headlights or emanating from street lamps.

Terms to Know

All astigmatism is not the same. There are two main types:

• Horizontal astigmatism occurs when the eye is shaped like a horizontal oval, wider than tall.

• Vertical astigmatism occurs when the eye is shaped like a vertical oval, taller from top to bottom than from side to side.

Your astigmatism may also be combined with other refractive errors, such as nearsightedness or farsightedness. So, you can be nearsighted (have trouble seeing clearly at a distance without correction) and have astigmatism. Or, you may be farsighted, typically with difficulty seeing up close, and have astigmatism.

Astigmatism That Gets Worse

If astigmatism is mild enough, you may only have slightly blurry vision. But if it gets worse, other symptoms may begin to arise, such as the following:

• Continuously squinting

• Developing eye strain

• Having headaches

• Having trouble doing tasks at night, such as driving

Also, those with worsening astigmatism only in one eye may develop refractive amblyopia, which has also been dubbed "lazy eye."

Uncorrected astigmatism is one cause of refractive amblyopia in children. The brain begins favoring the clearer images from the eye without astigmatism and starts to ignore the weaker eye with it, preventing the child's vision from developing properly.

Amblyopia can also happen when both eyes have a similar amount of moderate, uncorrected astigmatism, known as isometric amblyopia.

Signs that a child may be developing amblyopia from astigmatism may include:

• Head tilting

• Trouble with depth perception

• Squinting or closing one eye

• Astigmatism that is greater in one eye than the other or moderate to severe in both

If a child's amblyopia is not treated, normal vision may never develop. To avoid this, see an eye care provider who can correct the astigmatism and treat any amblyopia.

High amounts of astigmatism or advancing astigmatism can be a sign of keratoconus. In keratoconus, the cornea bulges into a cone shape rather than being a round dome.

Astigmatism Test: How to Know If You Have Symptoms

Determining if you have astigmatism means a trip to an ophthalmologist or optometrist. As part of an astigmatism diagnosis, you may expect to undergo a comprehensive eye exam, which involves the following:

• Visual acuity test: Reading the smallest letters possible on a Snellen eye chart or another type of eye chart helps determine how sharp your vision is.

• Retinoscopy: A retinoscope is a handheld device that shines a light into the eye. The eye specialist observes the reflection from the retina.

• Autorefractor: This instrument can determine how much astigmatism is present by shining a light in your eye and seeing how it changes as it moves through the eye.

• Phoropter: With this approach, you can look through a binocular-like device known as a phoropter and tell the eye specialist which correction you prefer.

• Keratometry: This kind of scan measures the curvature of your cornea.

How to Correct Astigmatism

Astigmatism can be corrected in variety of different ways. Here are some of the options:

Before Glasses or Contacts

No treatment may be necessary for mild astigmatism. Your eye specialist will help you determine if some correction, perhaps with glasses or contact lenses, is needed.

Glasses

You may be given glasses to correct astigmatism; if you already have glasses, a correction can be made to the lenses' prescription. This will ensure that the light strikes the retina in the correct place. But if you have a very large degree of astigmatism or keratoconus, glasses may be unable to correct it fully.

Contact Lenses

With mild astigmatism, traditional rigid gas-permeable or soft contact lenses can be used for correction.

Toric contact lenses, which may be rigid or soft, are needed for moderate astigmatism. They are designed to compensate for the irregular shape of the cornea. They must sit in the correct position on the eye's surface, which is often accomplished with weights added to the lens.

Surgery

Laser eye surgery procedures can permanently correct astigmatism by reshaping the cornea. This allows light rays to fall correctly on the light-sensitive retina. Whether you are a candidate for laser eye surgery depends on the amount of astigmatism. These procedures are not recommended if you have keratoconus.

Laser surgery for astigmatism can include any of the following procedures:

• Photorefractive keratectomy (PRK): PRK uses a special laser to reshape the cornea's surface.

• Laser in situ keratomileusis (LASIK): With LASIK, a flap is first cut, changes to the shape of the cornea are made, and the flap is replaced.

• Epi-LASIK: With this, an extremely thin flap is cut, and the cornea is reshaped underneath before the flap is replaced. Epi-LASIK is less invasive than traditional LASIK, and healing times may be quicker.

• Small incision lenticule extraction (SMILE): This technique involves making a tiny incision in the eye and removing a small disk-shaped piece of tissue, which changes the shape of the cornea.

Why Some People Have Astigmatism

If you are diagnosed with astigmatism, you may wonder how it developed, but what causes astigmatism is unclear. However, factors that may predispose you to astigmatism include:

• Having family members with astigmatism (there can be a hereditary connection)

• Being extremely nearsighted or farsighted

• Having a particularly thin cornea or one that is scarred

• Having undergone a surgical procedure like cataract removal or refractive correction (such as PRK or LASIK)

Where to Get an Eye Exam

Anyone who suspects they have astigmatism should seek a comprehensive eye exam from an ophthalmologist or an optometrist. If you do not have an eye specialist, ask those you know for a recommendation. A satisfied former patient can be a great source for finding an eye specialist you like.

You may also wish to look online to find practitioners in your area. You can find a nearby optometrist or locate an ophthalmologist this way.

Summary

Those with astigmatism may have trouble with blurry or distorted vision due to issues with the cornea or lens of the eye. This may lead to eye strain, headaches, and difficulty driving at night. If this is severe enough and not treated, it may lead to amblyopia, where vision doesn't develop properly.

Treatment options for astigmatism include glasses or contacts. For appropriate candidates, surgical correction may also be an option.

Read the original article on Verywell Health.