What is computer vision syndrome – and how can I prevent it?
Do you sit in front of a screen at work for hours, then leave with a headache, sore, dry, blurry eyes and a painful neck? If so, welcome to computer vision syndrome (CVS), a condition just waiting to happen to those who use a screen for more than three hours a day. This happens to be quite a lot of us – about 70 million worldwide. At the risk of being alarmist, some researchers argue that CVS is the “No 1 occupational hazard of the 21st century”. But back pain, tension headaches and discomfort are not inevitable consequences of screen time – perhaps we should simply be more careful. At the very least, we should encourage our children to develop good screen habits.
A study of 642 students in Iran between the ages of 11 and 18 found that about 70% used computers for at least two hours a day. Up to half reported eye strain, blurred vision, dry eyes and headaches. The symptoms were worse in those who were long- or short-sighted. While most got better quickly after coming way from the screen, some took a day to recover. About one-third sat too close to the screen.
What can we do about it?
Eyes work harder when they read from a screen because computer images are made of pixels, tiny dots that have a bright centre and blurred edges. Printed images and words, by comparison, are solid and well-defined. Our eyes constantly have to focus, relax and refocus to read the pixels, which tires out the muscles. The 20-20-20 rule to combat this says you should take a 20-second break every 20 minutes and focus on points 20ft from your computer. When we look at a screen, we don’t blink as much as we do normally, so consciously doing so will moisten your eyes and reduce irritation. Flat screens with anti-glare filters are kind to eyes, as is having adequate light. If you have glasses, check your prescription and consider lenses that reduce glare.
When it comes to the distance you sit from the screen, how you sit and the optimum level for reading documents, it becomes rather prescriptive. It’s more comfortable to look down at a screen, so keep yours 15 to 20 degrees below eye level (about 10-13cm, or 4-5in), as measured from the centre of the screen. The screen should be 46-66cm (18-26in) away from your face; any closer and your eyes have to work too hard to focus on the screen. Sit in a proper chair, even if it’s ugly, so you have support in the small of your back and can sit with your feet flat on the floor. Oh, and read more books – they are better for you.
It is estimated that globally, about 45 to 70 million people spend hours staring into a video display terminal, popularly known as computer screen. Several studies, mainly in developed countries, have shown an association between computer use and visual health related symptoms (Computer Vision Syndrome, CVS) in both children and adults. In this report, a review of literature on CVS was undertaken to determine the prevalence of CVS and compare the prevalence between studies. The risk factors associated with the syndrome range from individual visual problems and poor ergonomics.