Laser eye surgery (LASIK)

Last updated: March 16, 2009.

Don't stare at the Sun! It's something we all learn at a very early age: everyone knows it can blind you. So what's the deal with laser eye surgery (or LASIK, as it's properly called)? If looking at the Sun is harmful, how can staring into a blindingly bright laser improve your vision so you no longer need glasses or contact lenses? The difference between the Sun and a LASIK laser is simple: LASIK involves a meticulous procedure where a laser fires into your eye for nanoseconds at a time under precise, computer control. Let's take a closer look!

Photo: LASIK/LASEK laser eye surgery may be able to improve your vision, but it's not suitable for everyone—and you need to be aware of the risks. Please note that this is an artistic representation of laser surgery, not an actual illustration of what's involved.

Why might you need eye surgery?

Photo: Having eyeglasses can be very tedious. Fortunately, the ones you end up with are generally much more comfortable than the adjustable ones you get in opticians! Photo by courtesy of National Eye Institute, National Institutes of Health.

If you've worn eyeglasses or contact lenses for years, laser eye surgery can seem a very attractive option. Just imagine being able to see clearly without those clumsy optical attachments stuck in front of your eyes! The first you thing you need to understand is how the surgery does away with the need for those things.

The reason you need extra lenses is because the natural lenses inside your eyes don't do their job properly. When light from distant objects reaches your eyes, the lenses (one in each eye) are supposed to refract (bend) the rays so they focus on your retina. But that doesn't always happen:

• If you're short-sighted (myopic), the muscles in your eye don't relax enough, so the lens is slightly too fat and too strong. As a result, it brings light rays in to focus too soon, slightly in front of your retina, making distant things look blurred.
• If you're long-sighted (hyperopic), you have the opposite problem. Your eye muscles can't make the lens fat and strong enough. Light rays passing through the lens aren't bent inward enough so, by the time they reach your retina, they haven't quite come together in focus.

When you wear eyeglasses or contact lenses, the extra bit of glass or plastic compensates for the lenses in your eye so light rays focus perfectly on your retina.

What is laser eye surgery?

Now in theory, if we could operate on people's eyes to change the shape of their lenses, we could correct eye problems like this very easily. The trouble is, the lens is not on the outside of the eye: it's not easily accessible to an eye surgeon. Why not? Well, in front of the lens there's a thin, transparent protective coating called the cornea that you'd have to remove first. But here's a bit of luck. Since the cornea is curved, and not made of air, it also has an effect on light rays. In other words, it too behaves like a mild lens at the front of your eye. So the theory behind laser eye surgery is to change the shape of the cornea, very slightly, to compensate for problems in the lens behind it.

Photo: Eye anatomy: the main parts of the human eye. Photo by courtesy of National Eye Institute, National Institutes of Health.

The medical prefix for anything to do with the cornea is kerato; keratitis, for example, is the name given to an inflammation of the cornea, having surgery to remove part of your cornea is called a keratectomy, and reshaping your cornea is keratomileusis. So now you can see where surgeons got the name LASIK from: it stands for Laser-Assisted In-Situ Keratomileusis. In other words, using a laser to reshape your cornea. (Presumably in-situ means the process happens while you sit there and wait; you can't remove your eyeballs and mail them off for surgery—not yet, anyway.)

What does a LASIK operation involve in practice?

Photo: Corneal topography: Some time before you have laser eye surgery, you'll have an eye examination to establish how much treatment your corneas need. During that session, a computerized machine like this will make a map of your cornea so the surgeon can figure out which parts of the tissue need to be removed. Photo by Tony Tolley courtesy of RAF Lakenheath, US Air Force, and Defense Imagery.

Newspaper and magazine advertisements paint a seductive picture of LASIK as a simple walk-in procedure: walk-in with glasses like the bottoms of wine bottles; walk-out with 20-20 vision. This is really quite a misrepresentation. First, LASIK isn't suitable for everyone and absolutely doesn't guarantee perfect vision. Second, it's far from such a simple procedure: it typically involves a lengthy period of preparation before the laser operation and an even longer period of recovery lasting six months or more after the operation is done. Before the surgery, for example, you have to stop wearing contact lenses and eye makeup. If you wear hard lenses, you have to cease wearing them for weeks or even months before the surgery can take place (the exact period depending on how long you've been using them).

The operation itself is relatively simple and it's easy to understand. First, your eye is treated with an anesthetic, then your eyelids are gripped and held open by a suction frame. The same device pulls on the cornea and holds it securely in place ready for the surgery. It's not exactly painful, though it's not comfortable either. Next, using tiny bursts of powerful light lasting no more than a few nanoseconds, the laser cuts a flap in your cornea. (In some procedures, the flap is cut by a microscopic knife called a microkeratome blade.) Think of the flap as a bit like a small door in the surface of the cornea: it's cut on three sides but the fourth side is left attached to form a kind of hinge. The flap is then lifted up and folded back on the hinge to expose the inner corneal tissue underneath. Under computer control, the laser then reshapes the cornea under the flap. Once that's done, the flap is replaced and it will slowly reattach itself without any need for stitches or surgical adhesives.

Photo: An eye surgeon carries out LASIK surgery. Photo by Larry A. Simmons courtesy of US Air Force.

That's pretty much it—although you can't expect an instant improvement in your vision. First, you have to recover from the operation itself. You have to take antibiotics and other eyedrops to prevent infections and a syndrome called "dry eye." You also have to rest more and sleep with an eyeguard for several weeks to prevent damage while your eye recovers. You're not allowed to wear eye make-up, for the first few days, or take part in strenuous sports, for the first few weeks. Swimming pools and hot-tubs are usually off-limits for a couple of months.

Is laser surgery a good idea?

Since LASIK became available in the early 1990s, millions of people have benefited from a permanent improvement in their vision. Although few long-term studies have been done, over 90 percent of people who've had laser surgery reputedly achieve perfect or much-improved vision. Not surprisingly, a similar percentage of patients say they're satisfied with the results of their operation. Even so, laser eye surgery is by no means a miracle cure for bad eyesight, as government health agencies and consumer groups around the world have been at pains to point out. If you're considering having this treatment, be sure you're properly informed about everything it entails and make sure you have realistic expectations.

Photo: Even with LASIK, you won't be saying goodbye to eye charts: it's important to have your eyes examined regularly even after treatment. Photo courtesy of National Eye Institute, National Institutes of Health.

The first thing to note is that LASIK treatment is not suitable for everyone. While it may suit people with relatively mild short sight, for example, it's less suitable for those with very poor vision and it cannot address the gradual deterioration in close-up vision (presbyopia) that most people experience when they got older. A significant proportion of patients need a second operation called a retreatment, so you need to be prepared for that possibility. It's also important to realize that the recovery from laser-surgery can be uncomfortable and protracted. Some people experience painful side-effects and complications for months after their operation; a small number report that the operation has made their vision worse—and there have been numerous claims for damages.

In summary

The three key messages are these:

1. Remember that this is a serious surgical procedure and isn't something to be undertaken lightly. It's far more serious than simply opting to switch from glasses to contact lenses, for example.
2. Make sure you're fully informed about what the procedure entails and how long it may take you to recover. Don't fall for glossy advertisments and a hard-sell from an optical clinic.
3. Be sure you have realistic expectations about the outcome. Your vision may still not be perfect after the operation. You may need a retreatment. In the end, you may still need to wear eyeglasses for driving or some other activities.

Further reading

If you're thinking about laser eye surgery, you'll find these two websites helpful:

• Learning about LASIK: A very objective and informative website about the pros, cons, and risks of laser eye surgery from the US Food and Drug Administration (FDA).
• LASIK: Eye Smart: Another really informative website, this one from the American Academy of Ophthalmology.
• LASIK: This Wikipedia is also informative and (at the time of this writing) includes a very interesting section about the history of the treatment and how it was developed. The coverage is quite balanced and addresses the drawbacks of LASIK as well as the benefits.