Vision Correction Surgery


What is vision correction surgery?

Vision correction surgery, also called refractive eye surgery, is any surgical procedure used to correct refractive error. In recent years, tremendous advancements have been made in this field. After refractive surgery, many patients report seeing better than they had at any other time in their lives.

What is refractive error?

The goal of laser vision correction is to reduce refractive error and, by doing so, reduce or eliminate a patient’s need for glasses or contact lenses. Refractive error is an imbalance between the light-focusing power of the eye and the length of the eye, which leads to blurred images on the retina. Refractive error is expressed as the glasses’ strength in diopters (D) required to bring a distance image into focus on the retina.

There are several types of refractive error that can be addressed with laser vision correction:

  • Myopia (nearsightedness): Myopia is a condition in which the cornea focuses light too strongly relative to the length of the eye. In myopia, a distant image is focused in front of the retina rather than on it, which makes it harder to see than a near object. Laser vision correction can be used to selectively remove tissue from the center of the cornea, flatten its curvature, and move the focal point backwards onto the retina to allow better distance vision without glasses.
  • Hyperopia (farsightedness): In hyperopia, the cornea’s focusing power is too weak relative to the length of the eye. In this condition, images are blurred because the light rays reach the retina before they ever join together to a focused image. Although hyperopic patients are commonly referred to as “farsighted” because their distance vision is usually better than their near vision, these patients do not necessarily see well at distance, especially as they age and lose the lens’s near-focusing power (see presbyopia, below). Contrary to laser vision correction for myopia, laser treatments for hyperopia remove tissue from around the central cornea to steepen the center and increase its optical power. This moves the focal point forward onto the retina.
  • Astigmatism: Astigmatism can occur at the same time as myopia or hyperopia, and is usually targeted for correction in the same treatment. Astigmatism describes blur that results from asymmetry (unevenness) in the focusing power of the cornea or lens. A useful way to picture astigmatism is to compare an American football and a basketball. The curvature of a basketball, a perfect sphere, is the same no matter what perspective it is viewed from. A football, however, has different curvatures depending on what angle it is viewed from. Similarly, the cornea often has some degree of shape difference (astigmatism) that affects image focus, and spectacles (glasses) with “cylinder” correction or toric contact lenses are often used to correct this. In laser vision correction, the laser treatment profile is specially programmed to include a correction for astigmatism. Patients with very high astigmatism or irregular patterns of astigmatism require special consideration; their physicians may talk to them about alternatives to laser vision correction.
  • Presbyopia: Presbyopia is different from the first three refractive problems above because it eventually occurs in everyone, gradually progresses into the person’s late 60s and usually doesn’t affect baseline distance vision (except for some people with hyperopia). As we enter our 40s, the lens—an auto-focusing structure that is suspended behind the cornea—begins to lose its ability to relax (accommodate) into a steeper configuration for reading and other near work. People with no distance vision problems end up needing reading glasses because of this process. While laser vision correction does not reverse this process, your specialist can discuss your options for reducing dependence on reading glasses.

Procedure Details

What types of procedures are used for vision correction?

All vision correction surgeries work by reshaping the front part of the eye, so that light traveling through it is properly focused onto the retina located in the back of the eye. There are a number of different surgical procedures used to reshape the eye. The surgeon will help determine the best procedure based on eye measurements. Procedures include:

  • LASIK: Short for laser in-situ keratomileusis, this procedure is used to correct vision in people who are nearsighted, farsighted and/or have astigmatism. During LASIK, vision is corrected by reshaping underlying corneal tissue so that it can properly focus light into the eye and onto the retina. This procedure is most common and is performed by creating a flap with a laser in the outer layer of the cornea to reshape the layers underneath, resulting in fast healing time with minimal discomfort.
  • Photorefractive keratectomy (PRK): Short for photorefractive keratectomy, this procedure is also used to correct nearsightedness, farsightedness and/or astigmatism. During PRK, an eye surgeon uses a laser to reshape the cornea. This laser, which delivers a cool pulsing beam of ultraviolet light, is used on the surface of the cornea not underneath the cornea, like in LASIK. No cutting is required in this procedure, though the surface layer is removed during the surgery. This part of the eye grows back within the first few days after surgery. Patients may experience some discomfort after surgery and healing time may be somewhat longer than LASIK.
  • PHAKIC IOL: This procedure is performed by inserting an intraocular lens, much like the ones used in cataract surgery, in front of a patient’s own lens, without interrupting the surface layers. This procedure is typically used for patients with very nearsighted eyes. It is another option when procedures like LASIK or PRK are not possible.
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Risks / Benefits

Are these procedures safe and effective?

While the results of corrective surgeries have been promising, there are possible side effects. It is important to keep these side effects in mind when considering vision correction surgery.

  • Infection and delayed healing: Infection resulting from PRK occurs in one-tenth of 1% of patients. For LASIK, this number is even smaller. If an infection does result from surgery, it generally means added discomfort and a longer healing process.
  • Undercorrection or overcorrection: It is difficult to accurately predict the success of eye surgery until the eye has healed properly. Patients may still need to wear corrective lenses even after surgery. Often, surgeries resulting in undercorrections can be adjusted with a second surgery.
  • Worse vision: Occasionally the vision through corrective lenses is actually worse after the surgery than it was before surgery. This may be a result of irregular tissue removal or excess corneal haze.
  • Excess corneal haze: Corneal haze occurs as a part of the natural healing process after some of these procedures, including PRK. It usually has no effect on the final outcome of vision after surgery and can only be seen through an eye examination. Occasionally, however, this haze may affect a patient’s vision. A second surgery may be needed to correct it. The risk of corneal haze is much less with LASIK than it is with PRK.
  • Regression: Sometimes the effects of surgery gradually disappear over a period of several months or years. When this happens a second surgery is often recommended to achieve permanent results.
  • Halo effect: The halo effect is an optical effect that occurs in dim light. As the pupil enlarges, the untreated area on the outside of the cornea produces a second image. Occurring sometimes in patients having LASIK or PRK, this can affect and interfere with night driving, especially in patients who have big pupils in dark conditions. This side effect is less common with newer laser treatments and the halo effect usually goes away within the first year after treatment.
  • Dry eye: A very common side effect, dry eyes is an uncomfortable condition where the eye doesn’t make enough tears to moisturize the eye.

When to Call the Doctor

What questions should I ask before vision correction surgery?

Refractive surgeries require healthy eyes that are free from retinal problems, corneal scars and any eye disease. Beyond side effects, there are other questions to ask before deciding on refractive surgery, such as:

  • Will my insurance cover the cost?
  • How long will my recovery take?
  • Will there be any activity restrictions after surgery?

As technology progresses more and more, it is very important that you explore all options and possibilities before deciding which vision repair treatment is right for you.

Additional Details

Does insurance cover the costs of refractive or laser surgery?

Because refractive/laser surgery is usually an elective surgery, it is often considered cosmetic and not medically necessary. Your insurance may not cover the procedure. However, under certain conditions, medical insurance plans will cover refractive surgery.

These include:

  • Refractive errors that are a result of an injury.
  • Refractive errors that are a result of surgery.
  • Severe refractive errors. However, there is no standard level of impairment at which insurance will cover correction. Coverage under these circumstances is generally very inconsistent and individuals should check with their provider.
  • A patient is not only unable to wear glasses due physical limitation (such as an allergy or deformity) but cannot wear contacts due to physical limitation (lens intolerance).

Check with your insurance provider to learn more about your coverage for laser eye surgery.

Last reviewed by a Cleveland Clinic medical professional on 09/12/2019.


  • National Eye Institute. Refractive Errors. ( Accessed 9/13/2019.
  • U.S. Food and Drug Administration. What is LASIK? ( Accessed 9/13/2019.
  • National Eye Institute. Surgery for Refractive Errors. ( Accessed 9/13/2019.
  • American Academy of Ophthalmology. What is Photorefractive Keratectomy (PRK)? ( Accessed 9/13/2019.

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