How the Laser Works in Laser Eye Surgery

What is a Laser?

LASER stands for Light Amplification by Stimulated Emission of Radiation. The first word is a good place to begin. A laser is a light. Not a light like the one in your living room, but a special kind of light. It has unique qualities.

Monochromaticity - A laser has only one wavelength or color. A regular light bulb has a range of wavelengths.

Directionality - A laser has a narrow beam which does not diverge. Compare a laser pointer with a regular flashlight.

Intensity - A laser is an extremely powerful light. A simple laser can produce light which is a hundred times more intense than sunlight.

These properties make the laser useful in light shows, war games, and incidentally, health care. Within medicine, lasers were first adapted for eye surgery.

The Excimer Laser

Lasers are differentiated from each other by the wavelength of their light beam. A laser generated from krypton gas produces light with a wavelength of 647 nanometers (nm). This wavelength falls within the visible spectrum of electromagnetic radiation and is seen as red. An argon laser which is used in retinal surgery has a wavelength of 514 nm and is green. A holmium:YAG laser with a wavelength of 2.13 micrometers is useful in the treatment of hyperopia.

The excimer laser uses a combination of argon and fluoride gases to produce radiation in the ultraviolet range (193nm) which is invisible to the naked eye. This laser light has the ability to break molecular bonds in a process called photoablation.

In 1983, it was first realized that this laser could be useful for corneal surgery. Why? Because this laser was different. Unlike other lasers, the excimer had the ability to remove corneal tissue with a high degree of precision, and equally important, without causing thermal damage to the remaining tissue. Sculpting of the cornea entered into the realm of possibility.

It is difficult, yet desirable, to comprehend the degree of precision exhibited by the excimer laser. A millimeter is one thousandth of a meter or four hundredths of an inch. A micron, or micrometer, is one thousandth of a millimeter. That is, one millionth of a meter. For the sake of comparison, a potato chip is about 500 microns thick, a human hair is about 50 microns thick and a single red blood cell is seven microns in diameter. The excimer laser has the ability to sculpt the cornea within a fraction of a micron.

Advocates of laser eye surgery point out that the steadiest hands in the world cannot even approach that level of surgical precision.

There are other kinds of lasers on the horizon which act in a similar fashion to the excimer. The light from these solid state lasers is produced from a crystal, whereas the excimer beam is created from a gas. Technically, solid state lasers are not excimer lasers, but that's a whole new area to explore.

Before you have laser eye treatment, are you certain you fully understand the risks and implications of the procedures, and have you selected the right type of corrective eye surgery for your specific condition? Get all the facts that the ads don't tell you here.

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