Eye Health

23 February 2006

The eye

Remember how impressed you were when you saw the first cellphone that was a camera too? Well, that’s what billions of eyes manage to do every day – and we just take it for granted.

Remember how impressed you were when you saw the first cellphone that was a camera too? Well, that’s what billions of eyes manage to do every day – and we just take it for granted.

So, you don’t have X-ray vision and you kissed the wrong woman in the club, because it was so dark, but those peepers enable you to do a million things. Like your job, for instance. And watching a DVD, and making eye contact with the new receptionist, and playing golf. But how much do you really know about them?

The basics
There are some really strong muscles which are connected to the bone on the outer edges of your eye socket and to the outer layer of each eyeball. These muscles are moving constantly – even when you sleep. The brain controls the movement of these muscles and they move in the direction where you want them to, or where you see something interesting.

Light then bounces off that object, straight into your eye. This goes a long way to explaining why you cannot see in the pitch dark – there is no light. This then goes through your cornea, a see-through membrane that covers the whole front of your eye. The light continues its journey through the pupil – that black circle we all have in the middle of our eyes. The pupil, or rather the muscles around the pupil allow it to go bigger and smaller – smaller in bright sunshine and bigger in the dark. Think of your kitty – it’s the same principle at work here.

The light then shines against the retina, which functions like a big screen. It has two different kinds of nerve cells – rods and cones. These two types of cells convert light into nerve impulses, which travel along the optic nerve to the brain. Your brain then organises what it sees into something that makes sense. And, if you can believe it, this happens at a speed of 680 km/h. Good thing your optic nerve doesn’t have a driver’s licence.

When things go wrong
The eye is pretty well-protected. Firstly, it is basically inside a bone socket and secondly, the eyelids are programmed to close, well, at the blink of an eye, to state the obvious. Tears wash out the eye all the time to protect against foreign objects such as dust, bacteria and sand, which can get into your eye easily.

But, the eyes also show signs of ageing, as do other organs in the body. As we grow older, the lenses get harder and we can no longer read the telephone directory. For others, seeing faraway things become problematic. These two conditions are commonly known as nearsightedness and farsightedness.

There are many serious conditions that can affect the eyes, such as glaucomaglaucoma,macular degeneration and cataracts. Eyestrain and conjunctivitis can generally be treated quite easily.

Point is, it is worth your while to have your eyes checked out regularly, to get glasses or contacts if you need them and to have them seen to if anything untoward comes up. Many blind people manage to cope admirably, but life is simply easier if you can see. It’s as simple as that. Visit our Eye centre.

Interesting facts

  • When you have had too much to drink, your vision blurs. If you haven’t been drinking and this happens you should have it seen to immediately.
  • New-born babies focus best on objects that are between 20 and 35 cm away from the eyes – it takes a several weeks for them to learn to focus properly. Young babies prefer black and white patterns to bright colours and complex objects to simple ones.
  • Diabetics often develop serious eye problems later in life, and these can lead to blindness.
  • Cornea surgery can correct your vision to such an extent that you no longer need glasses or contact lenses.
  • Eating sufficient quantities of vitamins C and E and beta-carotene could slow down cataract development.

(Susan Erasmus, Health24, February 2006)


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Megan Goodman qualified as an optometrist from the University of Johannesburg and is currently practising at Tygerberg Academic Hospital in Cape Town. She has recently completed a Masters degree in Clinical Epidemiology at Stellenbosch University. She has a keen interest in ocular pathology and evidence based medicine as well as contact lenses.

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