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Before I Get LASIK: What Is a Laser?


Before I Get LASIK: What Is a Laser?[[MORE]]Most of us know about lasers from television. They’re the things that soldiers of the future shoot at robots of the future. Or they’re the things that future scientists use to blast apart the future...

Most of us know about lasers from television. They’re the things that soldiers of the future shoot at robots of the future. Or they’re the things that future scientists use to blast apart the future asteroid that is about crash into the Future Earth.

But real lasers are very much a part of modern, non-future life. And the highly sophisticated lasers involved in LASIK, while useless against marauding robots, can be used to help correct bad vision.

The basics

To understand how LASIK lasers work, you first have to understand lasers in general.

Lasers are a form of light that appear nowhere in nature, meaning that all lasers are necessarily created by human technology.  

The light you’re used to seeing (like the sun, etc.) is called “natural light.” Natural light is made up of many different wavelengths, each of which we see as a different color. Lasers, on the other hand, are monochromatic, meaning they consist of a single color (or wavelength).


As is implied by the name, wavelengths are literally shaped like waves. In natural light, the high points and low points of these waves don’t match up. In fact, they’re kind of all over the place. In laser light, all of the wavelengths move together. The high and low points of the waves line up perfectly, forming something scientists call “coherent” light.  

Natural light also tends to move in many different directions, which is why when you turn on a flashlight, you get a wide shaft of light instead of a single concentrated beam. Laser light is “collimated,” meaning it travels in one direction and can be concentrated on a single point in space.

The fact that laser light is monochromatic, coherent and collimated means that you can concentrate a tremendous amount of energy into a single beam of incredible power. This beam is useful for cutting through things, certainly, but in the last few decades, scientists have begun putting lasers to use in other remarkable ways — like LASIK.

How do you make a laser?

#DYK “laser” is an acronym? Well, it is: “light amplification by stimulated emission of radiation,” though that’s a bit of a mouthful.

The key there is the latter part of the acronym: “stimulated emission of radiation.” Laser light is created by stimulating electrons, usually with an electric current.


This stimulation causes the electrons to move into a higher-energy orbit around the nucleus of their particular atom. When the electrons stop being so ridiculously excited, they move back down to their original orbit and throw off photons, which is the basic particle of light.

Using mirrors, these photons are bounced around, stimulating even more electrons and causing them to drop even more photons. The end result is a ginormous number of photons creating a monochromatic (single color), coherent and collimated beam of powerful, concentrated light: a laser.

Putting lasers to work

Lasers have lots of practical uses — and some less practical. (Laser pointers? They should be called lazy pointers, AMIRITE?)

The first medical application of a laser was by a cardiovascular surgeon in 1962, who used one to remove plaque from the interior of a patient’s arteries.

Today, lasers are used in many different kinds of medicine: cosmetic dermatology, mammography, cancer treatment, angioplasty — even liposuction.

Two different kinds of lasers are used in most LASIK procedures.

The first, called a femtosecond laser, is a device that is capable of producing an ultrafast burst of energy. How ultrafast? Each burst lasts about a 700 femtoseconds, or 700 quadrillionths of a second.

The femtosecond laser is used to create a thin, temporary opening in the surface of the eye so that doctors can get to the cornea and go to work with the second laser, the excimer.


The excimer laser is a cold beam of ultraviolet light that doctors use to remove tiny amounts of tissue in the cornea, reshaping it so that it can better focus light into your retina, which may improve your vision.

LASIK isn’t for everyone and you can get more safety information here. LASIK patients may also experience some side effects, like dry eye or visual disturbances like halos, glares, starbursts or double images.

So what about the robot uprising?

While the excimer and femtosecond lasers will be relatively useless during the upcoming robot uprising, human ingenuity has given us other lasers that are tremendously powerful.

The U.S. Navy has one in service that can shoot down enemy missiles and drones, while Japanese researchers last year fired the most powerful laser in the history of the world. The latter consisted of a 2-petawatt pulse — or 2 trillion watts — discharged for about a trillionth of a second. To put that in perspective, 2 petawatts is about 1,000 times more power than the entire world consumes.



Lasers are concentrated beams of light capable of improving human vision and putting down robot uprisings. If the robots have humanlike eyes and exhibit good behavior while in captivity, we might be able to improve their vision, as well.

(They’ll have to meet a few other criteria, which you can find here.)

If you’re considering LASIK, you can find more information at

Pew pew, pew pew!

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