How does laser eye surgery work  - Dan Reinstein - video Dailymotion

TED-Ed

Explore the eye-opening science of LASIK: corrective laser eye surgery that focuses on reshaping the cornea to fix blurry vision.  --  In 1948, Spanish ophthalmologist Jose Ignacio Barraquer Moner was fed up with glasses. He wanted a solution for blurry vision that fixed the eye itself, without relying on external aids. The surgery he eventually devised was called “keratomileusis,” and his technique focused on reshaping the cornea— what we now know as LASIK. So how does laser eye surgery actually work? Dan Reinstein explains.  Lesson by Dan Reinstein, directed by Hype CG.

Transcript

00:00In 1948, Spanish ophthalmologist Jose Ignacio Barraquer-Monell

00:12was fed up with glasses.

00:14He wanted a solution for blurry vision that fixed the eye itself,

00:19without relying on external aids.

00:22But the surgery he eventually devised was not for the faint of heart.

00:26Barraquer began by slicing off the front of a patient's cornea

00:31and dunking it in liquid nitrogen.

00:34Using a miniature lathe, he ground the frozen cornea

00:38into the precise shape necessary to focus the patient's vision.

00:42Then he thawed the disc and sewed it back on.

00:46Barraquer called this procedure keratomileusis,

00:50from the Greek words for carving and cornea.

00:54And though it might sound grisly, his technique produced reliable results.

00:59So, how did Barraquer's surgery work?

01:03Keratomileusis corrects what are called refractive errors,

01:08imperfections in the way the eye focuses incoming light.

01:12Ideally, the cornea and lens work together to focus light

01:16on the surface of the retina.

01:18Several kinds of refractive errors can impair this delicate system.

01:23In people with myopia, or short-sightedness,

01:26a steep cornea focuses light just short of the retina.

01:31Those with hyperopia, or far-sightedness, have the opposite problem.

01:36Light is focused too far beyond the retina.

01:39And in people with astigmatism, the cornea has two different curvatures,

01:44which focus light at two distances and produce blurry vision.

01:49Even those with perfect vision will eventually suffer from presbyopia,

01:53or aging eyes.

01:55As the proteins in the lens age, they slowly increase its size.

02:01By an adult's mid-40s, the lens is too large to easily change shape and shift focus.

02:08Glasses and contact lenses bend light to compensate for these refractive errors.

02:14But, as Barraquer's procedure shows,

02:17we can also alter the shape of the cornea itself,

02:21moving the focal point backwards, forwards, or pulling a divided image together.

02:28And thankfully, modern eye surgeons can sculpt the cornea with far less invasive tools.

02:35In corrective laser eye surgery, surgeons rely on eczema lasers.

02:40These tools are accurate enough to etch words into a human hair.

02:46To safely accomplish these ultra-fine incisions,

02:50they use a technique called photoablation.

02:53This allows the lasers to essentially evaporate organic tissue

02:57without overheating surrounding eye tissue.

03:00So how does laser eye surgery actually work?

03:04The first step is to separate a thin layer from the front of the cornea.

03:08This can be done with either a flat, wide blade or a femtosecond laser

03:14that produces millions of tiny plasma bubbles

03:17to create a plane beneath the corneal surface.

03:21Surgeons then lift the flap to expose the inside of the cornea.

03:25Guided by the refractive error and the shape of the cornea,

03:29the eczema laser robotically sculpts the exposed corneal bed

03:33into the correct shape.

03:35This process usually takes less than 30 seconds for each eye.

03:40Finally, the flap is closed,

03:42and its edges reseal themselves in just a few hours.

03:46Because the lasering is done on the eyeball itself,

03:49it's described as in-situ or on-site.

03:53Its complete name is laser in-situ keratomyelusis,

03:57but you probably know it as LASIK.

04:00Essentially, this technique carves a patient's contact lens prescription

04:05onto their cornea.

04:07Like any surgical procedure, LASIK comes with certain risks.

04:10Some patients experience slightly blurred vision that can't be corrected by glasses.

04:15But the technique is currently about as likely to damage your eyes

04:19as wearing daily disposable contact lenses for one year.

04:23Today, a technique called SMILE enables surgeons to sculpt the cornea

04:28through even smaller incisions, further reducing recovery time.

04:32And lasers aren't just correcting the three types of refractive errors.

04:36This technology can also restore aging eyes.

04:40In a technique called laser-blended vision,

04:43surgeons adjust one eye to be slightly better at distance vision

04:47and the other to be better at close-range vision.

04:50The difference between the two eyes is small enough

04:53that most patients can merge their vision,

04:56allowing both eyes to work together at all distances.

05:00Advances in laser technology continue to make vision correction surgery

05:04more effective and accessible.

05:07One day soon, Baraker's vision of a world without glasses may finally come true.

05:30Use the tranquillum.

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How does laser eye surgery work - Dan Reinstein

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