How Lasik Works

Reshaping your corneas to give you clear vision is how Lasik works. It is an effective treatment for nearsightedness, farsightedness or astigmatism. But, there’s more to this procedure than just that simple answer. It shapes your cornea using a laser to remove corneal tissue. Once the cornea is the right shape you can focus your vision clearly.

Although Lasik is the most common surgery in the U.S., most people don’t know exactly what it is. In fact, most people don’t know that laser eye surgery has been done for years in a procedure known as photorefractive keratectomy (PRK).

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In this procedure the epithelium is removed to gain access to the corneal tissue. PRK was an improvement of a much older refractive surgery called automated lamellar keratoplasty (ALK). This surgery involved creating a flap of corneal tissue that was laid back. The exposed cornea was shaped manually with a knife. The flap preserved the epithelium as well.

In Lasik the epithelium is kept intact, attached to the corneal flap. The flap is replaced after surgery and reattaches during healing.

Two Methods For How Lasik Works

The conventional method of laser eye surgery has been performed for many years. It has a well-established success rate. In the conventional procedure, a suction ring is applied to the cornea.

Then the cornea is flattened making it possible to slice a thin flap. The microkeratome knife is used to cut this flap. Wavefront is a newer method of treating refractive errors.

This enhancement provides wavefront measurement data for diagnosis and treatment. As part of the diagnostics it customizes a precise map for creating the best corneal shape for each eye. During treatment it can guide the excimer laser to create that shape.

A Little History of Eye Surgery

Lasik is a combination of the best features of ALK and PRK, two earlier ablation procedures.

ALK, developed in the 1950s employs exposing the corneal tissue by cutting a flap and lifting it away, then manually removing corneal tissue in thin shavings with a microkeratome knife.

PRK was the first refractive surgery to use a laser instead of a microkeratome knife to shape the cornea.

In this procedure a brush is used to remove the epithelial cells giving access to the cornea. There is no flap. The laser is used to shape the cornea. The epithelial cells grow back during healing.

Lasik combines the flap from ALK with the laser ablation from PRK. The flap preserves the epithelial cells and makes a natural tissue “bandage” for the treated corneal tissue.

Advantages and Disadvantages of How Lasik Works

The advantages and disadvantages for these procedures are much the same. One difference is that wavefront ablation tends to increase higher order aberrations (HOA).

When HOA is already elevated conventional laser eye surgery may be a better choice.

Statistics on laser eye surgery outcomes are in the patient’s favor. Fewer than 5% experience bad outcomes, and most of those are easily corrected with a follow-up enhancement.

Fewer than 1% experience unsatisfactory outcomes that can’t be corrected. Not all bad outcomes are preventable. But, that’s to be expected in surgery. Sooner or later, someone will have a bad outcome. Whether you have conventional or wavefront Lasik most patients experience 20/40 or better vision.

The numbers reaching 20/20 or better without corrective lenses are slightly higher for wavefront than conventional laser eye surgery.

All experts agree that your surgeon’s experience and competence are the most important considerations. They all insist that choosing your physician carefully is your priority.

Make sure you ask the right questions about laser eye surgery before you choose the person who will change your vision for the rest of your life.

See our procedure-specific pages for risks, pros, cons, when that procedure is indicated and when it should be avoided.


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