Office workers often suspect that staring at a screen all day must be ruining their eyesight, but among the experts there seems to be a consensus that screens don't cause long-term damage to the eyes. Badly adjusted computer displays can, however, contribute to stress, discomfort and headaches. One of the most important factors that increase the load on the eyes is glare, which reduces the contrast between what one is trying to look at - text or graphics - and its background. Sunlight is the most noticeable form of glare, but the reflected image of an overhead lamp is also to be avoided. Both will cause eye and facial muscles to tighten, as the visual system strains to decipher the images. Another source of discomfort is flicker, caused by the interruptions created as the screen image is updated, dozens of times a second.
The computer industry incessantly encourages us to upgrade for the sake of trivial improvements in performance, but rarely urges us to upgrade for the sake of our comfort or wellbeing. But since we can't upgrade our eye muscles, upgrading our monitors may buy more happiness per pound than any other investment.
My own working life certainly changed with the acquisition of a new monitor, an LG Flatron 795FT+ (around pounds 300; Windows, and Mac with an adaptor). It's rather like buying a new car. You realise how much your old car must have deteriorated since you first got it - monitor displays worsen with age - and you're faced with a bunch of new features that have been introduced in the meantime. Like television sets, computer monitors now have a set of hoops to jump through, controlled via an on-screen display. The effort involved in getting through them puts you off ever adjusting the settings again. This is not ideal, since it may be helpful to vary brightness and contrast as ambient lighting levels alter. But the Flatron is designed to reduce glare, with a flat screen and special coatings to minimise intrusive reflections, allowing it to cope well with all but direct sunlight. It makes reading off the screen a pleasure, and that's saying something.
At 17 inches, it is larger than the standard home computer screen size of 15 inches. Intuitively, the increase in screen area seems a big improvement, though in fact, the larger the screen, the worse the fatiguing effects of flicker will be, whether or not the viewer is consciously aware of it. Professor Arnold Wilkins of Essex University, author of a book called Visual Stress, doubts that a 17-inch monitor is an improvement. He recommends that the working window be made as small as is practical, and that it be viewed against a dark desktop background. Since flicker is perceived mainly in the peripheral vision, a large screen will counteract the benefit of a small window.
By contrast, Tim Gopsill, National Health and Safety Officer of the National Union of Journalists, favours big screens and big windows. He also advises sitting directly in front of the screen, as far away from it as is comfortable, and looking out of the window from time to time, to alter focal distance. Rachel Benedyk, of University College London's Ergonomics Unit, says that you should avoid sticking to one working position and constantly change your posture.
Although the experts differ somewhat in their views, all seem to agree that what feels comfortable is likely to be easiest on the eyes. And if you're still worried about the effect that constant screen work is having on your vision, you have the right under Health and Safety legislation to ask your employer to provide an eye test.
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