ARE your eyes working overtime, what with the current screening of the World Cup 2010 football matches? Could a common component used in consumer electronics such as television and computer screens lead to eyestrain, headaches, and disturbed sleep?

It sounds alarmist, but in fact these claims are accepted as fact by experts in relevant fields. So what's the component? The blue LED (Light Emitting Diodes). Yes, those bright blue sparks of light on mobile phones, PCs, TVs, monitors, etc.

What's all the fuss about blue LEDs' Surely a light is just a light, no matter what the colour. How can there be a difference between blue and red, green, or amber?

In fact, blue light causes greater eyestrain and fatigue than other colours. It is harder for the eye to focus and causes greater glare and dazzle effects. It can also interfere with our internal body clocks, disrupting sleep patterns.

Too much TV damages eyesight

Television screens emit harmful blue lights. "Blue light is the most energetic portion of the visible light spectrum," says ophthalmologist Bernard Godley, of the Retina Foundation of the Southwest in Dallas, US.

"It's less energetic than UV radiation but it also has the ability to penetrate into tissue and cause cellular damage."

Also, when you look at an object for any length of time, your eye muscles are working, and the longer you focus on the object, the harder the eye muscles have to work. Therefore, when you watch TV without looking away from the screen, it makes your eyes tired.

Andrew Hogan, president of the Tasmanian division of the Optometrists Association Australia says everyone's eyes will benefit from a few simple TV viewing tips:

• When watching the television, sit at least four or five metres away from the screen - the closer you are to the object you're focusing on, the more tired your eyes will become.
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• Don't watch TV in a dark room - make sure the television is not the main light source in a room, but remember you don't want any glare or reflection on the screen.
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• Take a break - get up, move about and look around the room

Computer screens also emit harmful blue lights which can lead to vision impairment as well as eye strain. Computer work is indeed more tiring for the eyes than watching television, under normal circumstances.

The human eye is most relaxed when focusing in the distance (basically 5m away or more). Our eyes have to work harder to focus up close. A television also requires less concentration than reading print on a computer screen. Of course, appropriate spectacles and good visual habits can make computer work much easier for most of us.

Prolonged exposure to ultraviolet (UV) rays and harmful blue lights throughout the ageing process may cause excessive free radical damage to our eyes, which may lead to aged-related macular degeneration (AMD) and cataract.

Macular degeneration (AMD) affects one-third of those over the age of 75, and is the principal cause of visual disability in people over 65 years of age.

Macular degeneration is caused by the deterioration of the central portion of the retina, the inside back layer of the eye that records the images we see and sends them via the optic nerve from the eye to the brain. The retina's central portion, known as the macula, is responsible for focusing central vision in the eye, and it controls our ability to read, drive a car, recognise faces or colours, and see objects in fine detail.

Age is by far the greatest risk factor for cataracts. Cataracts are the leading cause of impaired vision and blindness worldwide, affecting up to 40% of people over 75.

The lens, which focuses light rays into the retina, is supposed to be transparent. When the lenses become opaque, the opaque areas are called cataracts.

They are most often caused by overexposure to the intense light (sunlight), but other factors can contribute to them: cigarette smoking, hereditary factors, injury, diabetes and some medications. Cataracts usually develop slowly, starting with blurred vision, spots, and the impression that a film is covering the eyes.

Fortunately, healthy retinas have a wide array of built-in chemical defences against UV-blue light damage. There are the more familiar agents vitamin E, vitamin C, lutein, and zeaxanthin. Unfortunately, these defences can weaken with disease, injury, neglect, and age.