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Speaker 1: Welcome to brain Stuff from How Stuff Works. Hey, brain Stuff,

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Speaker 1: I'm Lorn voc O Bomb and I've got another classic

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Speaker 1: brain Stuff episode for you Today. Our former host, Christian

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Speaker 1: Sager is here to explain these squeaky but life changing

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Speaker 1: science of how Lazik works. Hi, I'm Christian Sager, and

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Speaker 1: welcome to brain Stuff. When was the last time you

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Speaker 1: got to use an eyelid speculum? You know those small

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Speaker 1: metal prongs that push your eyelids open clockwork orange style,

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Speaker 1: well me drugs. I hope the answer is never. But

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Speaker 1: if you have been subject to one of these uncomfortable devices,

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Speaker 1: it's probably because you've had corrective surgery to your vision. See.

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Speaker 1: Our corneas are like windows that allow light to pass

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Speaker 1: through our retinas where it's converted into electrical signals to

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Speaker 1: our brain. If you have eyesight problems, it's usually because

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Speaker 1: your I can't focus an image onto your retina. For centuries,

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Speaker 1: we've really side on external lenses like glasses or contacts

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Speaker 1: for correction, But with modern technology, surgeons can actually alter

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Speaker 1: the shape of the eye itself using lasers to change

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Speaker 1: its focal point. The most popular technique is called LASIC,

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Speaker 1: which stands for laser assisted in puto karatoma LUSIS. It's

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Speaker 1: very effective at treating several visual problems, especially near sightedness.

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Speaker 1: Before any reputable eye doctor performs LASIC, they're going to

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Speaker 1: give you a thorough preoperative eye exam. They'll measure your

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Speaker 1: current prescription and manually check the surface of your cornea

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Speaker 1: with a dye called fluora cane. Other tests map your

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Speaker 1: corneas topography, and measure the exact diameter of your pupil.

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Speaker 1: To qualify for LASIC, you'll need to meet a certain

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Speaker 1: range of vision, corneal thickness, and pupil size. It's also

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Speaker 1: risky if you're pregnant, have severe heart problems, certain diseases,

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Speaker 1: or take some types of drugs. Once you've passed preopossessment,

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Speaker 1: you come back for the actual laser process, conducted by

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Speaker 1: both the surgeon and a technician operating the laser machine.

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Speaker 1: They'll put a topical anesthetic in your eyes to numb

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Speaker 1: any discomfort, and that's good because the next step is

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Speaker 1: to pry open your eyes with special tape and that

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Speaker 1: good old eyelid speculum. Then they'll calibrate the laser and

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Speaker 1: mark your cornea for alignment. Using a suction ring with

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Speaker 1: an extremely precise surgical blade called a micro kera tom.

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Speaker 1: The surgeon cuts a flap in your cornea and folds

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Speaker 1: it back. You'll be asked to focus on a red light,

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Speaker 1: which isn't the laser but helps center your eye. Now

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Speaker 1: it's laser time. A laser mixing reactive gases like chlorine

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Speaker 1: and fluorine with inert gases like argon, crypton, and xenon

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Speaker 1: produces a tightly focused beam of ultra violet light that

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Speaker 1: vaporizes a microscopic portion of the cornea. This is a

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Speaker 1: cool laser that doesn't heat the surrounding error surface. Instead,

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Speaker 1: it breaks down the molecular bonds of organic material seals.

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Speaker 1: The beam itself is microscopic, less than a nanometer wide.

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Speaker 1: The surgeon reshapes the cornea by controlling the size, position,

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Speaker 1: and number of laser pulses applied. Surprisingly, this only takes

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Speaker 1: a few seconds. When it's finished, your corneal flap is

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Speaker 1: replaced with a small antibiotic added. The cornea heels and rebonds,

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Speaker 1: immediately naturally sealing itself. Again. Taking into account the time

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Speaker 1: for both eyes, the entire procedure is usually done in

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Speaker 1: only fifteen to thirty minutes. After the operation, they'll give

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Speaker 1: you these cool I shields that prevents you from touching

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Speaker 1: your eyes but let you see enough to get around.

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Speaker 1: You'll wear them for the rest of the day and

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Speaker 1: sleep in a mask that night. Of course, someone has

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Speaker 1: to drive you home, and once you get there, you'll

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Speaker 1: need to apply rewedding drops, antibiotic drops, and possibly a

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Speaker 1: moisturizing gel inside your bottom eyelid. The ophthalmologist will follow

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Speaker 1: up the next day on a recurring basis for about

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Speaker 1: a year. Now you're probably asking, but Christian, couldn't there

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Speaker 1: be side effects when a doctor shoots a laser into

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Speaker 1: my eye? Well, yeah, of course there could. Most commonly,

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Speaker 1: eyes can be under corrected, overcorrected, or get a small

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Speaker 1: wrinkle when the corneal flap is replaced that causes a blur.

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Speaker 1: For the most part, these are easily fixed with a

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Speaker 1: second procedure. Sometimes a surgeon won't even recommend further refining,

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Speaker 1: since many recipients of lasik never achieve normal vision, but

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Speaker 1: do reduce their corrective prescriptions significantly. Other rarer side effects

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Speaker 1: can include halos around lights, light sensitivity, and double vision.

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Speaker 1: I'd be lying if I said there wasn't a chance

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Speaker 1: of partial or complete blindness, but it is minuscule compared

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Speaker 1: to the success rate. This is especially true if you're

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Speaker 1: seeing a reputable doctor. Keep in mind there are so

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Speaker 1: many unscrupulous practitioners out there that the f d A

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Speaker 1: actually had to issue a stern warning about dodgy sales

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Speaker 1: pitches underplaying the risk of lasik. But twenty five years

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Speaker 1: after it was invented by Golem Payman, Lasik is safer

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Speaker 1: than ever before. There's other types of eye surgery to

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Speaker 1: including radio carotatomy, automated lamellar carat to plastic and photo

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Speaker 1: refractive caretatomy. All of them, however, involved slicing up your

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Speaker 1: cornea to some degree. Today's episode was written by Christian

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Speaker 1: Sager and produced by Tyler Clang. To hear more from Christian,

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Speaker 1: check out his new pop culture podcast, super Context, and

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Speaker 1: of course, for more on this and lots of other

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Speaker 1: gross but fascinating topics, visit our home planet, how Stuff

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Speaker 1: Works dot com.