Christine L. Larsen, MD, is a board-certified ophthalmologist who serves as adjunct clinical faculty, specializing in glaucoma and cataract surgery, at the University of Minnesota.

If you have astigmatism , the cornea (the clear dome of the eye) or the lens that focuses rays on the light-sensitive retina at the back of the eye is shaped so that there can be competing focal points. You may have difficulty seeing clearly at any distance without corrective lenses.

Refractive laser surgery can correct astigmatism by using a laser to reshape the cornea. Techniques include laser-assisted in situ keratomileusis (LASIK), photorefractive keratectomy (PRK), and small incision lenticule extraction (SMILE).

This article will discuss how refractive laser surgery can correct astigmatism, what the contraindications may be (reasons against having the procedure), and potential risks. It will also highlight the purpose of laser refractive surgery, how to prepare, and what to expect.

With the aid of laser refractive procedures, surgeons can precisely reshape the cornea using various techniques.

The type of laser used depends on the refractive surgery chosen. An excimer laser can be used to ablate tissue (removing tiny amounts of tissue at a time from the outer surface of the cornea). Other procedures may rely on a femtosecond laser to make precise cuts, sometimes even below the surface.

Different techniques can work to effectively correct your astigmatism. Here's a look at each of these procedures.

The LASIK procedure involves cutting a flap in the cornea that can temporarily be laid back out of the way. This flap can be cut by the surgeon with a metal device known as a microkeratome, or this can instead be done with the aid of a femtosecond laser.

Once the flap is out of the way, an excimer laser can be used to ablate some tissue and evenly reshape the cornea to eliminate astigmatism, as well as to correct either nearsightedness or farsightedness. Once the procedure is done, the flap is laid back in place over the ablated section.

Nearsightedness (myopia) is trouble seeing things at a distance without correction. Farsightedness (hyperopia) is trouble seeing up close, as well as difficulty seeing clearly at all ranges.

With PRK, the excimer laser is used to ablate tissue and reshape the cornea for astigmatism, nearsightedness, or farsightedness. PRK can be used to treat up to 4 diopters (units of refractive power) of astigmatism, 12 diopters of myopia, or 6 diopters of hyperopia.

The difference with this procedure is that no flap is cut. Instead, the ablation is done right on the surface of the cornea.

The femtosecond laser can harmlessly penetrate through tissue. In the SMILE procedure, it is used to cut a small disc-shaped "lenticule" beneath the surface. This lenticule is thicker at the center and thinner at the rim. The lenticule is then removed through a small incision of less than 6 millimeters.

SMILE can be used to correct astigmatism from 0.75 diopters up to 3 diopters. It can also correct up to 10 diopters of nearsightedness.

Refractive surgery is usually only performed after your vision has stopped changing. To undergo a laser procedure, such as LASIK, you should not be younger than age 18. Other potential contraindications to be aware of include:

While refractive surgery is generally a safe and effective way to correct astigmatism, keep in mind that there can be complications. Undergoing laser refractive surgery can potentially leave you vulnerable to the following:

The purpose of undergoing this surgery to correct astigmatism is to reshape the cornea so that it is more symmetrical and can refract light rays down to a single point on the retina instead of several competing points that leave vision unclear.

At the same time, this surgery compensates for other refractive errors such as nearsightedness or farsightedness in which the focal point is either in front of or behind the retina instead of on the retina.

Laser refractive surgery takes place in an outpatient setting, which can include an ophthalmologist's office. You will not need to stay overnight.

You should arrange to take the day off from school or work and plan to nap or relax after surgery. You will need somebody to drive you home after your surgery. As the surgery often takes an hour or less, your driver may wish to bring you and wait till you are ready to go home.

Your surgeon will advise you whether you need to stop wearing your contacts before surgery. This is done because contacts can change the shape of your cornea. Stop wearing eye makeup two days before surgery.

Wear comfortable clothing. Bring your insurance card and any needed paperwork.

When you show up the day of surgery, expect whatever laser refractive surgery you undergo to be brief. These procedures only take about 10 minutes per eye. The steps for both LASIK and PRK are very similar. These include the following:

For SMILE similar steps will be taken, as well as some slightly different ones:

After undergoing laser refractive surgery to correct astigmatism, expect to relax for the rest of the day. Keep in mind that you will need to have someone drive you home from the procedure.

Your vision may be slightly blurry at first, but within a day or two, it should clear. You should then be able to partake in your usual activities, with the exception of anything that may get your eyes wet, such as swimming.

You should also avoid strenuous activity, particularly anything that may leave the eye vulnerable to injury such as boxing, football, or karate.

After undergoing a refractive laser procedure, visit your ophthalmologist or optometrist regularly. No matter which procedure is used to correct your refraction, changes can occur in your eyes over time. You may need to wear corrective lenses or wish to undergo an enhancement surgery.

With astigmatism, seeing clearly at any distance without correction can be challenging. That's because the uneven cornea causes competing focal points on the retina. It is possible to undergo laser refractive surgery with LASIK, PRK, or SMILE to correct your vision. These are all outpatient surgical procedures.

With LASIK, a corneal flap is made and the LASIK ablation is done underneath. For PRK, the tissue ablation is done right on the surface. For SMILE, a lenticule of tissue is cut beneath the surface and removed through a small incision. All can reshape the cornea in a more symmetrical way and improve vision.

Those with astigmatism may feel tied to their glasses or contact lenses to see clearly. Laser refractive surgery can reshape irregularities in the eye causing astigmatism and correct other refractive errors such as nearsightedness and farsightedness. This enables many to be less dependent on glasses and contacts.

University of Rochester Medical Center. Types of eye surgery for refractive errors.

American Academy of Ophthalmology. LASIK -- laser eye surgery.

Stanford Medicine. Photorefractive keratectomy (PRK).

American Refractive Surgery Council. SMILE.

US Food and Drug Administration. When is LASIK not for me?

American Academy of Ophthalmology. Introduction to SMILE.

American Refractive Surgery Council. LASIK complications and LASIK eye surgery risks.

American Academy of Ophthalmology. What is small incision lenticule extraction?

Food and Drug Administration. What should I expect before, during, and after surgery.

Refractive Surgery Council. LASIK enhancements: LASIK touch-up facts.

By Maxine Lipner Maxine Lipner is a long-time health and medical writer with over 30 years of experience covering ophthalmology, oncology, and general health and wellness.

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