Eye Surgery for Refractive Errors

Surgery for correcting or improving refractive errors:

Clear vision depends on how well the cornea and lens permit light rays to fall onto the retina. Light rays must be refracted (bent) to focus on the retina. The retina is the light-sensitive nerve layer that lines the back of the eye, which creates impulses from the light rays that are sent through the optic nerve to the brain.

If the cornea or eye shape is abnormal, vision can become blurry because light does not fall properly on the retina. Called a refractive error, an abnormal cornea shape can often be corrected by refractive eye surgery, which, in turn, corrects the vision problem. Refractive errors can include myopia (nearsightedness), hyperopia (farsightedness), astigmatism (an irregularly shaped cornea which causes blurring), and presbyopia (similar to hyperopia, a condition which causes the lens to harden).

The goal of most refractive eye surgeries is to reduce or eliminate a person's dependency on eyeglasses or contact lenses. Refractive eye surgery is not for everyone. One type of surgery may be more suitable for one person than another. Always consult your physician for a diagnosis and to discuss which type of surgery, if any, may be appropriate for you.

There are several types of corrective surgical procedures for refractive errors, including, but not limited to:

* laser in-situ keratomileusis (LASIK) surgery/wavefront-guided LASIK
* photorefractive keratectomy (PRK)
* radial keratotomy (RK)
* astigmatic keratotomy (AK)
* automated lamellar keratoplasty (ALK)
* laser thermal keratoplasty (LTK)
* conductive keratoplasty (CK)
* intracorneal ring (Intacs)

What is LASIK surgery?

LASIK, or laser in-situ keratomileusis, surgery is used to correct nearsightedness. When a person is nearsighted (myopic), his or her eye is too long or the cornea is too steep, resulting in too much focusing power. The light rays entering the eye come in focus before hitting the retina, resulting in blurry vision when looking in the distance. The procedure, which should be performed by a skilled eye surgeon, involves reshaping the cornea using an excimer laser. LASIK is replacing many of the other refractive eye surgery techniques.

A promising new technology, called wavefront-guided LASIK, provides an advanced method for measuring optical distortions in the eye. The Eye Surgery Education Council states that physicians can now use this technology as a roadmap to evaluate the eye by measuring how light is distorted as it passes into the eye and then is reflected back. This creates an optical map of the eye, highlighting individual imperfections. In addition, the wavefront technology allows the surgeon to tailor the laser beam settings for a more precise procedure. This provides a patient sharper, better quality vision as well as a reduction in nighttime vision difficulties.
How is LASIK surgery performed?

Although each procedure varies slightly, in general, LASIK surgery involves using a computer-controlled excimer laser (a cold, ultraviolet laser) and a microkeratome (a surgical instrument). With these instruments, the surgeon cuts a flap in the center of the cornea to remove a thin layer of tissue. By removing the tissue, the cornea flattens, reducing the myopia. The flap, which is replaced without using sutures, adheres back to the cornea within minutes.
Recovery after LASIK surgery:

In most cases, recovery from LASIK surgery is fast and involves minimal discomfort. Mild pain relievers may be recommended by your surgeon to relieve discomfort during the first day after surgery. Patients typically take eyedrops for a week after the procedure.
Possible side effects of LASIK surgery:

Generally, LASIK has a high success rate. However, side effects do occur. The following are the most common side effects and complications. Each individual may experience side effects differently. Side effects may include:

* dry eyes (during the healing process)
* eye discomfort (mostly during the first 24 hours following surgery)
* irregular astigmatism, which can decrease the corrected vision (astigmatism means blurring caused by an irregularly shaped cornea)
* corneal haze or glare
* overcorrected or undercorrected vision
* inability to wear contact lenses in the future
* loss of the corneal flap, requiring a corneal graft
* scarring
* infection
* vision loss

Benefits of LASIK surgery:

For most candidates, LASIK surgery usually involves little pain and recovery is rapid. Other benefits may include:

* LASIK can correct a wide range of myopia, up to 15 diopters (unit of measurement of the refractive power of a lens).
* LASIK can be repeated to correct the vision further.
* The eyes stabilize between three and six months after LASIK surgery.
* The eye is not weakened, because only one flap is cut into the cornea.
* LASIK usually causes little or no scarring of the cornea.
* Post-operative care is usually limited to using eye drops for a week after surgery.

What is photorefractive keratectomy (PRK) surgery?

Photorefractive keratectomy, or PRK, uses the same excimer laser used in LASIK surgery and is performed to reshape the cornea in an attempt to correct mild to moderate myopia (nearsightedness). According to the US Food and Drug Administration (FDA), PRK has a 95 percent success rate. Only about 15 percent of patients need glasses, occasionally, following surgery.
How is PRK surgery performed?

Although each procedure varies slightly, in general, PRK surgery involves an excimer laser beam reshaping the cornea by removing microscopic amounts of tissue from the outer surface. The procedure, which generally only takes a few minutes, uses a computer which maps the eye's surface and calculates the required corneal change.
Possible side effects of PRK surgery:

Generally, PRK surgery has a high success rate. However, side effects do occur. Because the corneal surface is cut, it takes several weeks to heal. In addition, there is some eye discomfort following the surgery that may last for several weeks. The following are the most common side effects and complications. Each individual may experience side effects differently. Side effects may include:

* mild corneal haze (following surgery)
* glare or halos around light (this side effect may be present for months following the procedure)

Who is a potential candidate for LASIK or PRK eye surgery?

According to the US Food and Drug Administration (FDA), potential candidates for corrective laser eye surgery must meet the following criteria. However, it is advised that potential candidates consult his/her physician before undergoing any type of corrective eye surgery. The criteria include:

* The candidate must be at least 21 years old if being treated with the Summit laser (one brand of excimer lasers), or 18 years old if being treated with the VISX laser (another brand of excimer lasers). This age requirement is necessary to ensure the eyes have finished growing.
* The candidate must have mild to moderate nearsightedness (myopia).
* The candidate must be free of eye disease, problems with the retina, or scarring of the cornea.
* The candidate must have the financial ability to pay for this costly surgery, since insurance may not cover the procedure.
* The candidate must be aware of all the side effects, risks, and benefits of the surgery. Candidates should also be aware of the alternative treatment options available.

What is radial keratotomy (RK) surgery?

Radial keratotomy surgery, or RK, is a procedure also used to correct myopia (nearsightedness). The procedure involves making microscopic, radial incisions (keratotomies) in the cornea to alter the curvature of the cornea, thus, correcting light refraction. Hundreds of thousands of people who qualified for this type of surgery have undergone the procedure successfully since its introduction to the US in 1978.
How is RK surgery performed?

Although each procedure varies slightly, in general, RK surgery involves an eye surgeon cutting (with a calibrated diamond scalpel) radial or spoke-like incisions into the cornea outside of the center of the cornea (also called the optical zone, which is the area where a person sees through). Due to pressure inside the eye, the incisions cause the center, or optical zone, of the cornea to flatten, reducing refraction.
Possible side effects of RK surgery:

One main side effect of RK surgery is the excessive amount of time it takes for the cornea to heal. In some cases, healing may take weeks. The following are the most common side effects and complications. Each individual may experience side effects differently. Side effects may include:

* a weakened cornea that can rupture
* increased risk of infection
* difficulty in fitting contact lenses, if needed
* discomfort
* glare around lights
* fluctuating vision during the first few months
* cataracts (a change in the structure of the crystalline lens that causes blurred vision)
* loss of vision