Refractive surgery changes the way your eye refracts light.  It isn't for everyone.  But if you are a good candidate, it can dramatically change the way you see.

So what makes a good candidate?  The basic requirements include:

• be over 18 years old (if you're younger than that, your vision may still be changing)
• have no active eye disease, such as glaucoma
• have a stable eyeglass prescription for at least two years.
• have vision correctable to at least 20/40.
• have healthy corneas.

You're probably not a good candidate if you have:

• extreme myopia (high myopes can get a phakic IOL which is an implant placed inside the eye)
• thin corneas
• large pupils
• very dry eyes
• severe autoimmune diseases such as rheumatoid arthritis and Sjogren's Syndrome (some patients have very mild autoimmune disease which is no longer a contraindication)
• advanced glaucoma or other serious eye conditions (some patients with well controlled glaucoma may have refractive surgery)

You're not a candidate if you:

• have cataracts
• are pregnant
• are taking certain drugs (including the acne medicine Accutane)

Also, if you're seriously involved in contact sports such as wrestling, boxing, and martial arts, be aware that a severe eye injury after this surgery could cause your vision to worsen.  In these instances, most doctors recommend not having Lasik but rather PRK where there is not risk of flap dislocation with severe eye trauma.

The goal of refractive surgery is to change the way the eye refracts light by changing the shape of the cornea.  One of the earliest forms of this surgery is called radial keratotomy (RK), discovered by accident by a Russian doctor, Svyatoslav Fyodorov.  After removing glass from a patient's eye, the doctor found that the patient's vision had unexpectedly improved.

By the late 1970s, RK was being practiced in the U.S.  In RK, the surgeon makes a series of radial incisions in the cornea using a precision calibrated diamond knife.  Radial means the cuts extend out from the center of the cornea to its edge, like the spokes of a wheel.

Today, lasers are used instead of knives, and RK has largely fallen out of favor in the U.S.  A few years ago, the most popular form of laser based refractive surgery was PRK, an acronym for photorefractive keratectomy.  In this procedure, the surgeon first removes the thin outer layer of the cornea, called the epithelium, then uses an excimer laser (a type of laser that does not produce heat) to shave off cells from the cornea, changing its curvature.  A computer system assures precision by guiding the laser's movement.  The epithelium grows back naturally, forming itself around the cornea's new shape.

LASEK, an acronym for laser-assisted sub-epithelial keratectomy, is a variation of PRK in which the epithelium is not removed.  Instead, the surgeon cuts into it and peels it back, like a flap.  Then, as in PRK, the excimer laser reshapes the cornea. After the reshaping, the flap of epithelium is put back into place.  About 10% of refractive surgeries are done using PRK or LASEK.  PRK or LASEK are often recommended to patients with thin corneas or marginally dry eyes, or in individuals who are at risk for a severe eye injury, such as a boxer. 

But today, the refractive surgery of choice – and the subject of this episode of Second Opinion – is clearly LASIK, an acronym for laser in situ keratomileusis.  In this procedure, the surgeon makes a flap in the cornea itself, using an instrument called a microkeratome, or a special cutting laser.  The process takes only a few seconds. 

Then, as in the other procedures, an excimer laser removes a very small amount of tissue from the inner portion of the cornea.  Again, a computer system guides the surgery.  The laser's action has been pre-programmed to reshape the cornea to the precise dimensions that will give the patient the maximum correction.  This part of the surgery normally takes no more than a few minutes.  Finally, the flap of cornea is put back into place, where it quickly bonds to the reshaped cornea's surface.  This also takes only a few minutes.

If you choose to have LASIK surgery, you'll find it's an outpatient procedure, and usually takes less than 10 minutes per eye.  But you'll probably be at the doctor's office for about an hour-and-a-half.

You will need someone to drive you home from the surgery and will need a day or two of recovery time.  It may take a month or two for your vision to fully stabilize, but normally you'll notice the results of the surgery within a few days. You may also notice that distant objects don't look as crisp and clear as they might.  This problem has been common enough that artists, photographers, craftspeople and others should be aware of it.

After surgery, roughly 5-10 percent of patients have problems, such as under or over correction, that might require one or more secondary procedures.

The most common potential complications from the surgery are:

• dry eye
• problems with night vision
• hazy or blurry daytime vision

However, these side effects usually disappear after three months. 

A second set of problems occur less than five percent of the time, six months to a year after surgery, and seem to depend on the type of laser used.  These are: 

• seeing halos, glare and starburst patterns when looking at lights
• ghosts and double images
• problems seeing in dim light
• feeling that "something" is in your eye
• sensitivity to light
• red eyes

Finally, serious complications happen to less than one percent of patients.  These include:

• infections in the corneal flap
• pain or discomfort
• loss of best corrected vision (your vision with glasses or contacts)
• swelling or pressure in the eye

However, in general, LASIK surgery has an extremely high success rate.  Federal Food and Drug Administration statistics say that 92% to 95% of patients achieve 20/40 vision within six months of surgery. That's good enough to drive without glasses.