Overview of Refractive and Laser Eye Surgery

Last Editorial Review: 6/30/2005
The Cleveland Clinic


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

All refractive and laser eye surgeries work by reshaping the cornea, or clear 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 types of refractive or laser eye surgeries used to reshape the cornea, including:

  • LASIK: Short for laser in-situ keratomileusis, this laser eye surgery is used to correct vision in people who are nearsighted , farsighted , and/or have astigmatism . During LASIK laser eye surgery, vision is corrected by reshaping underlying corneal tissue so that it can properly focus light into the eye and onto the retina. LASIK laser eye surgery differs from others in that a flap is made in the outer layer of the cornea so that the underlying tissue can be accessed.
  • PRK: Short for photorefractive keratectomy, this laser eye surgery is used to correct mild to moderate nearsightedness, farsightedness, and/or astigmatism. During PRK laser eye surgery, 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 laser eye surgery. Therefore, no cutting is required.
  • LASEK: Short for laser epithelial keratomileusis, this is a newer form of laser eye surgery that combines many of the benefits of LASIK and PRK. However, unlike LASIK and PRK laser eye surgeries, there is no cutting or scraping of the eye. Instead an epitheal flap is created using a 20% alcohol solution. LASEK laser eye surgery is used to treat nearsightedness, farsightedness, and astigmatism.
  • ALK: Short for automated lamellar keratoplasty, this eye surgery is used to correct vision in people with severe nearsightedness and slight degrees of farsightedness. As in LASIK laser eye surgery, a flap is created in the cornea so that the doctor can reach the underlying tissue. However, during this procedure, a laser is not used to correct vision. Instead, another incision is made on the sub layer of the cornea to reshape the cornea.
  • LTK: Short for laser thermokeratoplasty, this is a new laser eye surgery is used to treat farsightedness and astigmatism. During LTK laser eye surgery, a laser beam uses heat to shrink and reshape the cornea. Vision is corrected in a matter of seconds, without any cutting or removal of tissue.
  • AK: Short for astigmatic keratotomy, this is not laser eye surgery, but a surgical procedure used to correct astigmatism. The cornea of people who have astigmatism is shaped like a football. AK eye surgery corrects astigmatism by making one or two incisions at the steepest part of the cornea. These incisions cause the cornea to relax and take a more rounded shape. This eye surgery may be used alone, or in combination with other laser eye surgeries such as PRK, LASIK, or RK.
  • RK: Short for radial keratotomy, this eye surgery was once one of the most frequently used procedures to correct nearsightedness. However, since the development of more effective laser eye surgeries, such as LASIK and PRK, RK is rarely used today.

Are Refractive and Laser Eye Surgeries Safe and Effective?

While the results of laser eye surgeries have been promising, there are possible side effects. It is important to keep these side effects in mind when considering refractive or laser eye surgery.

  • Infection and delayed healing. Infection resulting from PRK occurs in one-tenth of one percent of patients. For LASIK laser eye surgery, this number is even smaller. If an infection does result from refractive or laser eye surgery, it generally means added discomfort and a longer healing process.
  • Undercorrection or overcorrection. It is difficult to accurately predict the success of refractive or laser eye surgery until the eye has healed properly. Patients may still need to wear corrective lenses even after laser eye surgery. Often surgeries resulting in undercorrections can be adjusted with a second laser eye surgery.
  • Worse vision. Occasionally the vision through corrective lenses is actually worse after refractive or laser eye surgery than it was before. 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 refractive or laser eye surgeries, including PRK. It usually has no effect on the final outcome of vision after laser eye surgery and can only be seen through an eye examination. Occasionally, however, this haze may affect a patient's vision. A second refractive or laser eye surgery may be needed to correct it. The risk of corneal haze is much less with LASIK laser eye surgery than it is with PRK.
  • Regression. Sometimes the effects of refractive or laser eye surgery gradually disappear over a period of several months. 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 laser eye surgery or PRK, this can affect and interfere with night driving, especially in patients who have big pupils in dark conditions.
  • Flap damage or loss. This is a risk factor with LASIK laser eye surgery only. Instead of creating a hinged flap on the central cornea that can be closed, the entire flap may detach, risking permanent damage to the cornea.
Refractive and laser eye 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 or laser eye surgery, such as:

  • Will your insurance cover the cost of laser eye surgery? How long will recovery take?
  • Will there be any activity restrictions after laser eye 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.

Reviewed by the doctors at The Cleveland Clinic Cole Eye Institute.

Edited by Charlotte E. Grayson, MD, WebMD, October 2004.

Portions of this page © The Cleveland Clinic 2000-2005


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