Welcome to brain Stuff from How Stuff Works. Hey, brain Stuff, I'm Lorn voc O Bomb and I've got another classic brain Stuff episode for you Today. Our former host, Christian Sager is here to explain these squeaky but life changing science of how Lazik works. Hi, I'm Christian Sager, and welcome to brain Stuff. When was the last time you got to use an eyelid speculum? You know those small metal prongs that push your eyelids open clockwork orange style,
well me drugs. I hope the answer is never. But if you have been subject to one of these uncomfortable devices, it's probably because you've had corrective surgery to your vision. See. Our corneas are like windows that allow light to pass through our retinas where it's converted into electrical signals to our brain. If you have eyesight problems, it's usually because
your I can't focus an image onto your retina. For centuries, we've really side on external lenses like glasses or contacts for correction, But with modern technology, surgeons can actually alter the shape of the eye itself using lasers to change its focal point. The most popular technique is called LASIC, which stands for laser assisted in puto karatoma LUSIS. It's very effective at treating several visual problems, especially near sightedness.
Before any reputable eye doctor performs LASIC, they're going to give you a thorough preoperative eye exam. They'll measure your current prescription and manually check the surface of your cornea with a dye called fluora cane. Other tests map your corneas topography, and measure the exact diameter of your pupil. To qualify for LASIC, you'll need to meet a certain range of vision, corneal thickness, and pupil size. It's also risky if you're pregnant, have severe heart problems, certain diseases,
or take some types of drugs. Once you've passed preopossessment, you come back for the actual laser process, conducted by both the surgeon and a technician operating the laser machine. They'll put a topical anesthetic in your eyes to numb any discomfort, and that's good because the next step is to pry open your eyes with special tape and that good old eyelid speculum. Then they'll calibrate the laser and
mark your cornea for alignment. Using a suction ring with an extremely precise surgical blade called a micro kera tom. The surgeon cuts a flap in your cornea and folds it back. You'll be asked to focus on a red light, which isn't the laser but helps center your eye. Now it's laser time. A laser mixing reactive gases like chlorine and fluorine with inert gases like argon, crypton, and xenon produces a tightly focused beam of ultra violet light that
vaporizes a microscopic portion of the cornea. This is a cool laser that doesn't heat the surrounding error surface. Instead, it breaks down the molecular bonds of organic material seals. The beam itself is microscopic, less than a nanometer wide. The surgeon reshapes the cornea by controlling the size, position, and number of laser pulses applied. Surprisingly, this only takes a few seconds. When it's finished, your corneal flap is
replaced with a small antibiotic added. The cornea heels and rebonds, immediately naturally sealing itself. Again. Taking into account the time for both eyes, the entire procedure is usually done in only fifteen to thirty minutes. After the operation, they'll give you these cool I shields that prevents you from touching your eyes but let you see enough to get around. You'll wear them for the rest of the day and
sleep in a mask that night. Of course, someone has to drive you home, and once you get there, you'll need to apply rewedding drops, antibiotic drops, and possibly a moisturizing gel inside your bottom eyelid. The ophthalmologist will follow up the next day on a recurring basis for about a year. Now you're probably asking, but Christian, couldn't there be side effects when a doctor shoots a laser into
my eye? Well, yeah, of course there could. Most commonly, eyes can be under corrected, overcorrected, or get a small wrinkle when the corneal flap is replaced that causes a blur. For the most part, these are easily fixed with a second procedure. Sometimes a surgeon won't even recommend further refining, since many recipients of lasik never achieve normal vision, but
do reduce their corrective prescriptions significantly. Other rarer side effects can include halos around lights, light sensitivity, and double vision. I'd be lying if I said there wasn't a chance of partial or complete blindness, but it is minuscule compared to the success rate. This is especially true if you're seeing a reputable doctor. Keep in mind there are so many unscrupulous practitioners out there that the f d A actually had to issue a stern warning about dodgy sales
pitches underplaying the risk of lasik. But twenty five years after it was invented by Golem Payman, Lasik is safer than ever before. There's other types of eye surgery to including radio carotatomy, automated lamellar carat to plastic and photo refractive caretatomy. All of them, however, involved slicing up your cornea to some degree. Today's episode was written by Christian
Sager and produced by Tyler Clang. To hear more from Christian, check out his new pop culture podcast, super Context, and of course, for more on this and lots of other gross but fascinating topics, visit our home planet, how Stuff Works dot com.