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Everything You Ever Wanted To Know About Laser Eye Surgery

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EYES
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If you've just about had it with the glasses and contact lenses, perhaps you're considering laser eye surgery to correct your vision. But what does the procedure really entail? What are the risks? And will you have guaranteed perfect vision afterward?

We asked Dr. Sonia Yoo, M.D., professor of ophthalmology at the Bascom Palmer Eye Institute at the University of Miami Health System, and Dr. James Salz, M.D., a Los-Angeles based refractive and cataract surgeon and clinical spokesperson for the American Academy of Ophthalmology, to answer the questions we've always wondered about getting corrective vision surgery -- specifically, LASIK, which is undergone by about 700,000 Americans a year.

Is laser-assisted-in-situ keratomileusis (LASIK) the only kind of vision-correcting laser surgery there is?
No, though it is the most popular. There are several other options, including photorefractive keratectomy (better known as PRK) which, like LASIK, is used to correct nearsightedness, farsightedness and astigmatism. PRK was invented before LASIK, but LASIK is more commonly used than PRK. Both PRK and LASIK involve using a laser to reshape the cornea. The only difference is that LASIK involves making a flap in the cornea, and the laser treatment is actually done to the part under the flap of the cornea, Yoo explains. Meanwhile, with PRK, the laser treatment is done right on the surface of the cornea, without the flap.

Why might someone choose PRK over LASIK (and vice versa)?
While there is really no difference in results or safety between the two procedures if a patient qualifies for both, there are some factors that might make someone choose one kind of laser eye surgery over the other, notes Salz. A person might choose LASIK over PRK because LASIK provides much faster results. For instance: While PRK patients need four to seven days before their vision is good enough to drive, LASIK patients can usually see well enough the day after the procedure to drive themselves to their post-op appointment. "So LASIK is basically driven by the patients, by the consumers. They've decided they like it better," Salz says. "So nationwide, you'll find probably 90 percent of patients that have surgery have LASIK, and 10 percent have PRK."

However, a person might opt for PRK over LASIK if he or she might be at risk for complications from the flap that is made in the cornea in LASIK (examples: people with a thin cornea, or people who might have recreational needs -- like being a boxer or basketball player -- where they might have an increased risk of being poked in the eye), Yoo says. In addition, LASIK doesn't change the structural integrity of the cornea as much as PRK does, so if there's something in a screening exam that might make a surgeon concerned that the cornea will not hold its shape after the laser treatment, the patient might be advised to undergo PRK over LASIK.

Who is LASIK not right for?
The only way to tell if LASIK is right -- or not right -- for you is to talk with your eye doctor. Factors that could affect someone's choice to undergo LASIK involve having dry eye syndrome, having thin corneas (as mentioned above), having very high levels of refractive error, and having the corneal condition keratoconus, among others, according to the American Academy of Ophthalmology.

Can LASIK really give you perfect vision?
Yes... but not everyone may experience this, and even then, there are caveats (which is why if you see a LASIK provider advertising guaranteed 20/20 vision, be wary). If your eyes really aren't that bad -- meaning you have a prescription for -1 or -2, you likely won't stand to gain much from the procedure. But if you are at least moderately nearsighted -- say, around a -5 or -6? "These patients have a lot to gain and [their] results are excellent," Salz says. Meanwhile, people with a -9 or -10 prescription who are unable to see the large E on an eye chart unless they get about 3 feet from the chart "have the most to gain from LASIK".

If your vision after the first LASIK procedure isn't exactly as you'd hoped, it is possible to undergo a reoperation. (People with the worst eyesight going into a LASIK procedure may have a slightly higher risk of requiring a reoperation.) "We can lift the flap [made during the first procedure] back up, you don't need to make a new flap," Salz says. These types of reoperations are "very accurate usually because the amount of correction is very low."

Overall, the majority of people undergoing LASIK -- more than 90 percent -- will achieve somewhere between 20/20 and 20/40 vision, without the need for contact lenses or glasses, according to the American Academy of Ophthalmology.

Can the effects of LASIK wear off?
Everyone's eyes change as they get older. There's even a word for it: presbyopia, which is Greek for "old eye." So "even if you've never needed any glasses your whole life, when you get into your early- to mid-40s, you're going to have trouble reading," Salz says. LASIK patients are no exception. "If you fix patients who used to be nearsighted, and all of a sudden they have presbyopia, they're either going to have to get a pair of reading glasses like everyone else, or you could do a [reoperation] and make one eye nearsighted and one farsighted," which is called monovision.

Because your eyesight can change with time, don't assume that you will never need to wear glasses or contact lenses again, notes the American Academy of Ophthalmology.

Is it possible to be too old or too young to have LASIK?
If you don't have significant astigmatism, the minimum age for LASIK is 18, Yoo says. With significant astigmatism, the age rises to 21. The American Academy of Ophthalmology also points out that ideally, a person will not get LASIK done until after age 21, since a person's eyes may still be changing up until that point. (It's also possible for a person's eyesight to keep changing after 21, too.)

In that same vein, people who are pregnant or nursing are likely not good LASIK candidates because their refractive error may be changing.

Can your eyes be too "bad" to have LASIK?
If a person has a healthy cornea of normal thickness, he or she can have a diopter (the unit used to measure correction) of up to -9 or -10 and still have LASIK done, Salz says. For people whose eyes are worse than that, they may instead be candidates for another refractive surgery procedure that involves putting an artificial lens inside the eye, in front of their natural lens. "We do that in patients who are extremely nearsighted and you can't completely correct them with LASIK surgery," he says.

What exactly is the laser doing to the eyeball to make eyesight better?
What occurs during LASIK is called "photoablation" -- it's not burning, and it's not shaving, but it's ablating, meaning that it's removing tissue.

"The laser is in a wavelength of ultraviolet light, so you can't see the laser treating the tissue. You don't actually see the tissue being removed in slices or anything like that," Yoo says. "But there is a little bit of a plume. It's not quite smoke, but it's a plume of tissue from when the tissue ablates."

What the laser is actually doing is reshaping the cornea. If you're nearsighted, that means your cornea is too steep, so the laser will flatten the central cornea. Meanwhile, if you're farsighted and the cornea is too flat, the laser may reshape it to have a "donut" shape in the periphery of the cornea, to essentially steepen the center.

Does it hurt?
There is no pain during the procedure, Salz says. The patient might feel a little pressure on the eye, when the doctor is making the flap (which takes about 15 seconds), because there is a suction device on the eye. "If you close your eyelid and press on your eye firmly with your thumb, you simulate the pressure feeling you get when you make the LASIK flap," he says.

The laser portion of the treatment to actually correct the vision, which takes less than a minute, also doesn't cause any pain because the doctor will apply numbing drops to the eyeball beforehand.

What about afterward?
After the procedure, the patient may experience some pain or sensitivity because the topical anesthesia will have worn off about 15 to 20 minutes after the procedure has finished. "They might have discomfort, usually scratchiness in their eye, some tearing, light sensitivity," Yoo says. "With LASIK, that feeling lasts about four to six hours. Patients will usually go home and sleep it off and maybe take some pain medicine, and they can't scratch their eyes."

What is the recovery like?
As mentioned above, a person will usually be able to see well enough to drive on the day after the procedure.

What are the biggest risks or complications associated with LASIK?
Overcorrection or undercorrection of eyesight, as well as the potential for still having a prescription even after your LASIK surgery, are the most common risks, Yoo says.

Infection is a risk of any surgical procedure -- and the same is true for LASIK. Fortunately, "the risk of infection is really low, one out of a couple thousand patients, and most of those infections are peripheral -- meaning, they don't lead to loss of vision usually," Salz says. However, it's still a risk to consider. Other complications include bumping the eye and moving the flap, which would cause little wrinkles to develop under the flap (in such a case, the patient would have to get the flap straightened out), as well as inflammation under the flap, which can be treated with cortisone drops.

A patient can also experience glare or halos, particularly at nighttime, though those symptoms will resolve for most people three to six months after surgery, Yoo says. However, there is a small percentage of patients who have persistent glare or halos even after that six-month period.

Editor's Note: This article is not meant to be taken as medical advice for, or against, laser eye surgery. The only way to decide if laser eye surgery is right for you is to discuss the risks and benefits of the procedure with your eye doctor.