Some work days can be nothing but headaches, but if you’re consistently ending the day with a pounding head, itchy, dry eyes and blurry vision, you could be suffering from the modern scourge of Internet use: CVS.

CVS, is short for Computer Vision Syndrome, a term optometrists have given to the particular form of eye strain that comes from looking at computer and other device screens all day.

A study released earlier this year by the U.S.-based Vision Council found that more than 90 per cent of us spend at least two hours a day looking at screens, whether it’s our phones, tablets, TVs or computers. One-third of us spend nine hours or more in front of screens. And CVS can kick in after just two hours of uninterrupted screen use.

There are a few reasons why screens are hard on our eyes. For one, the letters in screen text is not as sharply defined as it is on a page, forcing us to strain a little to focus. When we look at a screens closely for several hours, we use our eyes’ ciliary muscles to help our eyes focus at short distances, but holding that muscle contracted for hours without rest is tiring, leading to strain.

What’s more, while we usually blink about 18 times a minute in regular life, we tend not to blink much at all during up-close focusing, causing our eyes to dry out. All these factors can add up to foggy vision, headaches, and twitching eyelids. Some even experience double vision, dizziness or nausea.

The good news is that, contrary to what your mother might have told you, sitting in front of a screen all day will not make you go blind. In fact, there’s no evidence that CVS causes any kind of long-lasting eye damage.

And while the symptoms fade away after digital device use, there are easy ways to prevent CVS in the first place. Here are a few of them:

Follow the 20-20-20 rule

Groups including the Ontario Association of Optometrists suggest we follow the 20-20-20 rule. That simply means we stop staring at our computers every 20 minutes to spend 20 seconds or more looking at objects 20 feet away – or far enough away that our eyes don't have to work to focus.

The 20-20-20 rule gives our eye muscles a short break and allows us to blink to rehydrate our corneal surface

To break bad screen habits, the Ontario Association of Optometrists has created 20-second daydream videos to help computer users remember the 20/20/20 rule.

Change your workstation setup

Raffael Dickreuter

The best way to set up your computer, optometrists say, is to have the screen about 50 to 70 centimetres away from your eyes -- or about an arm’s length.

It’s also best to look slightly downward at your screen, as that will allow the eyelid to cover at least a portion of the eye and keep it moist. Ideally, the centre of the screen should be 20 degrees below eye level, or about 10 centimetres down.

Adjust the text size to make it as large as you can without embarrassing yourself among your colleagues. This can be done in your computer settings, or by clicking Ctrl and the plus sign when viewing a webpage.

Make sure there are no reflections or glare on your screen, and adjust the brightness of your screens to be similar to the brightness of the room. As a test, if the white background of this webpage looks like a light source, it's probably too bright.

Also make sure your digital screens and eyeglasses are clean so that you don't have to strain to see the screen clearly. Finally, if you don’t have much humidity in the room, use a humidifier to prevent your eyes from drying out.

Take longer breaks

Set a timer on your computer or device to ensure you get up at least once an hour (and walk away from the screen for five minutes or more). Not only will you give your eyes a break, but getting up and moving around once in a while is good for the rest of you.

What’s more, research has shown repeatedly that taking breaks during work can improve both our productivity and our ability to retain information we're reading. That break can be as simple as skipping email to speak to a colleague directly, or getting up to walk down for a tea before settling back into work.

Go for regular eye exams


If you’re noticing a lot of headaches or other Computer Vision Syndrome symptoms, it could be a sign you have other vision problems. It’s possible, for example, you need glasses or a new prescription. Or it could be a sign of a more serious vision problem, so it’s recommended you get your eyes checked every two years, at least, in order to spot problems early.

If you have a lot of computer time in your day and you still have CVS symptoms after making these adjustments, your optometrist might recommend computer glasses, which have an anti-reflective coating and are tinted to block short-wavelength, blue light emitted from computer screens, which research is beginning to show may worsen eye strain.