Digital eye strain: what works and what doesn't

It has a name and it is not “tired eyes”. It is called computer vision syndrome, or digital eye strain, and the American Optometric Association describes it as the group of eye and vision-related problems that appear after prolonged use of a computer, tablet or phone.

The important thing about that name is what it implies. It is not a problem with the eye. It is a problem with what we are asking the eye to do.

The real symptoms

• Dry, gritty or watering eyes at the end of the day.
• Blurred vision that comes and goes, particularly when you look up from the screen and take a few seconds to focus into the distance.
• Headache, almost always in the forehead or around the eyes.
• Neck and shoulder pain. It is on the list because it is part of the same picture: your posture is set by your eyes.
• Sensitivity to light.
• Occasional double vision.

The symptoms ease when you leave the screen. If they do not ease, or if they also appear when reading on paper or driving, stop reading this article and book an eye examination.

Why it happens

You stop blinking

This is the main mechanism and the least known. Under normal conditions we blink about fifteen times a minute. In front of a screen, according to the American Academy of Ophthalmology, we drop to five or seven.

Each blink spreads the tear film across the cornea. Blinking a third as often means the surface of the eye spends the day evaporating. Hence the stinging, the grittiness and the blur that clears when you blink hard.

Focusing gets no rest

Focusing up close is muscular work. Four hours in a row at the same distance are four hours of sustained contraction. The blur when you look into the distance is that muscle taking its time to let go.

The eyes converge all day

To look at something close, both eyes turn inwards. Holding that convergence for hours is tiring, and far more tiring if the coordination between the two eyes is not quite right. That is a problem which does not show up in a standard visual acuity test.

What does work

The 20-20-20 rule

Every 20 minutes, look for 20 seconds at something 20 feet away, about six metres. In practice: the window, the end of the corridor, the street.

It does for focusing what a break does for anything else: it lets go. It is what the American Academy of Ophthalmology recommends instead of buying special glasses.

It is worth being honest about the backing for it. It is a sensible, universally accepted recommendation whose experimental evidence is thinner than its fame suggests. But it costs nothing, it has no drawbacks and it attacks the right mechanism. Set an alarm for the first week. By the second you will not need one.

Blink on purpose

It sounds ridiculous written down. It works all the same. Every time you finish a paragraph or an email, close your eyes tightly for two seconds. It is what the American Academy of Ophthalmology explicitly recommends, and it is the only gesture that attacks the main cause.

Distance and height

• About 64 centimetres, roughly the length of your arm, between your eyes and the screen.
• The screen slightly below eye level, so your gaze falls a little downwards. That way the eyelid covers more of the eye’s surface and it dries out less.
• If you work with papers, put them on a stand at the same distance as the screen. Every change of distance is one more focusing cycle.

Light

• Match the screen brightness to the light level of the room. A screen that looks like a torch in a dark room is tiring; a dim screen in a sunlit room forces you to strain.
• Turn up the contrast and the text size. Nobody wins a prize for reading at 9 point.
• Get rid of reflections. A window or a lamp reflected in the glass steals contrast without your noticing. Turn the desk ninety degrees before buying anything.

The air

Air conditioning and fans pointed at your face dry out the ocular surface. The American Academy of Ophthalmology lists them among the environmental causes of dry eye, along with car air vents. In Puerto de Mazarrón this counts: from June to September almost everybody works with the air conditioning on.

Redirect the outlet and, if it helps, put a glass of water nearby. And do not confuse an eye that waters all the time with a moist eye: reflex tearing is a typical response to a dry eye.

What does not work

Blue-light filtering glasses. The American Academy of Ophthalmology does not recommend them for computer use, and points out that several studies suggest they do not improve the symptoms of digital eye strain. The cause of the strain is not the colour of the screen’s light. It is the blinking, the sustained focusing and the distance.

We explain it in detail in our article on blue-light filters, because it deserves a whole article.

When the problem is the prescription

This is the section that justifies an eye examination, and the one an internet article cannot resolve.

There are patterns of eye strain that none of the measures above will fix, because the origin is in the optical correction. The most common:

• A small uncorrected astigmatism. It does not blur enough for you to notice it, but it makes the eye correct its focus continuously. It is suspect number one for the frontal headache in mid-afternoon.
• Presbyopia beginning. Between 40 and 45, many people still read well but at the cost of increasing effort. The symptoms arrive before the blur does.
• Progressive lenses with the screen badly resolved. If you lift your chin to see the monitor, your glasses are dictating your posture. There the answer is usually an occupational lens.
• Reading glasses from the chemist. They come with the same power in both eyes and the distance between the optical centres is always the same. If your eyes are not identical, or your pupillary distance is not the one in the mould, you are straining to compensate for glasses that are not yours. As an emergency stopgap they are fine. As eight-hour glasses, no.
• A convergence insufficiency. The eyes do not sustain the effort of turning inwards well. It is detected with binocular vision tests, not with the letter chart.
• Underlying dry eye, aggravated by the screen but not caused by it.

What to bring to your appointment

Say how many hours you spend in front of a screen and at what distance. Bring your current glasses, all of them. And if you can, measure with a tape the real distance between your eyes and your monitor at home, sitting the way you actually sit. That number is more useful than any general answer.

An examination that takes eye strain into account does not stop at measuring how much you see. It measures how your two eyes focus and coordinate, and it examines the ocular surface. If it turns out in the end that your prescription is fine and all you need is to move the desk and drink more water, we will tell you that too.