Welcome to brain stuff from How Stuff 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. WELLEMI 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 eye can't focus an image onto your retina. For centuries, we've relied 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 karatma 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 flu or a 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 preopp assessment, you come back for the actual LASIC 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 eye 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 cornia 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 ultraviolet light that vaporizes a microscopic portion of the cornea. This is a cool laser that doesn't heat the surrounding air or surface. Instead, it breaks down the molecular bonds of organic materials. 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 eye 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 paste 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 risks of lasik. But twenty five years after it was invented by Golem payment, lasic is safer than ever before. There's other types of eye surgery to including radial car atautomy, automated lamellar keratoplast see, and photo refractive care atatomy. All of them, however, involved
slicing up your cornea to some degree. Check out the brainstuff channel on YouTube, and for more on this and thousands of other topics, visit how stuff works dot com