PRK

Both PRK and LASIK use the excimer laser to reshape the cornea to the desired power.

Understanding How the Excimer Laser Works

Excimer laser correction of myopia and astigmatism is the most technologically advanced medical procedure available today to reduce the dependence on glasses and contact lenses. The excimer laser reshapes the front surface of the eye with a cool beam of light energy. The term "excimer" is a contraction of the words "excited" and "dimer", which describe the creation of the laser beam.

The most common form of excimer laser procedure is called P.R.K (Photoreactive Keratectomy). Another is called L.A.S.I.K. (Laser-Assisted Intrastromal Keratomileusis). Both are outpatient surgical procedures. Hundreds of thousands of patients have improved their vision as a result of excimer laser technology.

The laser light beam is produced by mixing different gases in a high voltage cavity. This produces a beam with a wavelength of 193 nanometers which can remove molecules of tissue with virtually no heat or damage to surrounding tissue. Guided by a sophisticated computer, the light beam is used to vaporize superficial eye tissue by breaking molecular bonds. The excimer is so precise that each pulse can remove 39 millionths of an inch of tissue in 12 billionths of a second. The excimer laser is also used industrially to etch computer microchips because of the extremely fine precision and smoothness of this type of laser beam.

The excimer is used for two primary procedures: P.R.K. and L.A.S.I.K.

P.R.K. uses the laser to gently reshape the outer surface of the cornea (the clear outermost layer of the eye). Deeper layers remain virtually untouched. The laser reshapes the corneal surface in seconds. This reshaping enables light entering the eye to be focused on the back of the eye, resulting in clearer vision. Since the laser removes only a very thin layer of the cornea, the cornea keeps its original strength.

LASIK combines the precision of the excimer laser with a procedure that has been performed manually for more than 20 years. The benefit of LASIK is that it can provide patients with severe and extreme cases of myopia and astigmatism, with more successful results.

The more nearsighted the eye is, the more tissue that is removed and the longer the reshaping process takes for both procedures. Even the most severe cases require only about one minute of laser application, removing less than 20% of the cornea's thickness. Nine out of ten myopic patients require less than 30 seconds of laser treatment and a layer as slender as a human hair is removed.

Over 750,000 patients around the world have had the laser procedure performed.

It is projected to become the most common procedure performed worldwide within the next five years.

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