Friday, November 19, 2010

LASIK

Nowadays we have spectacles of different shapes and sizes, and also contact lens to help us see better. But still, nothing beats looking at the world without an object between our eyes and our subject. People spent thousands to get their vision fixed via LASIK, so it is somewhat a lucrative business.


I was assigned to do a presentation on "laser in medicine" yesterday, and I found something interesting.

Ever heard of the term LASIK?
It stands for Laser Assisted In-Situ keratomileusis.
Why do they call it LASIK instead of LAISK? Well you have to ask the person who derived that name.

Image:http://www.explainthatstuff.com/lasereyesurgery.html
We often hear people talk about getting their eyes fixed by going through a LASIK surgery. How does a laser fix our eyes? How do they use the laser to cure far and short-sightedness?

Well the concept is pretty simple, one just have to know the trick behind it.

We get short/farsightedness when the biological lens in our eyes becomes defective. The lens thickness changes with age and behavior(reading in the dark) and so our vision becomes blurry.

To alleviate the problem, ophthalmologists came up with spectacles, which dates back to 5th century BC, when the Egyptians(told u they are smart) made "simple glass meniscal lenses".

Image: spectaclesblog.com
Nowadays we have spectacles of different shapes and sizes, and also contact lens to help us see better. But still, nothing beats looking at the world without an object between our eyes and our subject. People pour out thousands to get their vision fixed via LASIK, so it is somewhat a lucrative business.

We couldn't see clearly because the muscles in our eyeballs that hold the lens loosen, hence thickening the lens. Thus the light that comes in doesn't get refracted correctly and falls at a distance away from our retina. We call that short-sightedness.

Image: bbc.co.uk
For far-sightedness, the light ray falls behind the retina.

Image: Lasikguider.com
The obvious solution to fix this problem is to tighten/loosen our lens, correct? Well.. no. Spectacles and contact lens set up another lens in front of our biological lens to make up a two-lenses system, which is very troublesome especially when doing sports or...trying to look good. Some bloggers, for example those blogging about LASIK, possess amazingly good-looking face =P

Image: http://www.explainthatstuff.com/lasereyesurgery.html
But then, our biological lens is not easily accessible to surgeons, and normally surgeons would try to minimize the level of surgical invasion to reduce the risk of sustaining long term injury to the eyes.

There is a way, though.
Well, in front of the lens there's a thin, transparent protective coating called the cornea. Since the cornea is curved, and not made of air, it also has an effect on light rays. In other words, it too behaves like a mild lens at the front of your eye. So the theory behind laser eye surgery is, lo and behold, to change the shape of the cornea, very slightly, to compensate for problems in the lens behind it.

Image: medicineworld.org
Bingo~! So the surgeon would grind or SLICE away a little bit of your cornea to fix your vision. And since our eyes are pretty sensitive, we need something that is precise and safe, which leads us to laser. Lasers are used to do the job, because lasers are basically a beam of light that doesn't diverge with distance, and very powerful. So it offers a suitable tool to grind away layers of our cornea safely and precisely.

The medical prefix for anything to do with the cornea is kerato; keratitis, for example, is the name given to an inflammation of the cornea. Having surgery to remove part of your cornea is called a keratectomy, and reshaping your cornea is keratomileusis.

An operation to remove the cornea. Image: Freewebs.com
So now you can see where surgeons got the name LASIK from: Laser Assisted In-Situ Keratomileusis. In other words, using a laser to reshape your cornea. (Presumably in-situ means the process happens while you sit there and wait; you can't remove your eyeballs and send them off for surgery—not yet, anyway.)




Malcolm
info:
http://www.explainthatstuff.com/lasereyesurgery.html


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