You’ve been looking at the computer all day. You have a slight headache and your eyes are blurring. You look around and have trouble focusing the book shelf, which is only three metres away. Sounds familiar?

You start thinking: This can’t be good for my health, before I know it my 20:20, naturally perfect, vision will decline. I’ll need glasses and children will pick on me and call me “four eyes”.

But, will they?

Fortunately, the answer is no. Children no longer refer to people with glasses as four eyes. Plus, according to the science there is no definitive link between staring closely at a computer screen and short sightedness. So what is happening to your eyes when they go blurry? And is it actually bad for your health?

The long and short of being short sighted

“Short sightedness”, or myopia, is a condition where distant objects appear fuzzy, but objects that are close look clear. When light comes through your eye it first hits the cornea and then the lens. The cornea and lens are curved surfaces that bend the light to make it hit the retina. A person with myopia has a longer eye than usual, or their cornea is too curved. As a result the light bends, but doesn’t hit the retina in the correct spot. This means that you can’t focus on objects that are far away without corrective glasses. (Glasses bend the light so it hits the retina correctly).

Could this happen to me when I stare at the computer?

Probably not. “Near work” is the technical term for visual activities that happen about 40 centimetres (16 inches) from the eye. This includes reading a book, knitting, and staring at a computer screen. Several studies have searched for a link between near work and short sightedness, and they haven’t found one yet.
Scientists reckon that some people are susceptible to developing myopia from near work, but it’s only a small subset of vulnerable people.

What are the risk factors for myopia?

Risk factors that have been spotted are hereditary factors (i.e. if your parents are short sighted), and the amount of time children spend in the sun. A recent Australian study compared two groups of children: both spent the same amount of time watching TV, reading and playing computer games. But the outdoor group spent two hours a day outside, and the other spent only 30 minutes outside. The results? The outside group had much fewer instances of myopia. Aussie researchers thought that the sun might help the eyeball grow and develop during childhood.

If I’m not going short sighted – why are my eyes fuzzy after staring at the computer?

After you’ve been gazing into the eyes of Google many people experience uncomfortable symptoms – like difficulty focusing on objects, and tension headaches. But, it’s not myopia developing, it’s eye strain.

The muscle around your eyes, called the ciliary muscle, is getting tired. This muscle controls the shape of our lens, allowing it to curve and focus on objects that are close and faraway. Staring at a computer screen for several hours forces our ciliary muscle to keep working, and stay contracted at the same tension for long periods of time. This is quite tiring for the muscle.

The tired ciliary muscle might give you headaches, and difficulty focusing on distant objects. While the mechanism hasn’t been proven scientifically, some researchers think that it might take a while for the muscle to snap out of its contracted state, and relax. While it’s still contracting the lens and cornea will stay curved at a particular point. This means you can only focus on nearby objects.

Another reason for the fuzzy vision is blinking. We normally blink around 10-15 times per minute. But using a computer can drop it to as low as seven times a minute.  Blinking spreads tears over the surface of the eye. When we stop blinking the surface of the cornea dries out: clouding the once transparent cornea, and causing blurry vision.

Computers make us particularly susceptible to blurry vision from dry eyes because unlike when we read a paper, we are staring at the computer screen straight on.  This increases the surface area of the cornea, making our eyes vulnerable to drying out. (When we read text on paper we are normally looking downwards, and the eyelid covers a large part of the front of our eye, stopping the tears evaporating.)

How long do these symptoms last?

Both the tired ciliary muscle and dry eyes are a short term phenomenon, and only last a few hours. Once we start blinking and relaxing the muscle they go away, with no long term side effects to worry about.

What can you do to prevent eye strain?

• Give your eyes a rest. Take regular breaks and look around at distant objects or close your eyes.
• Move your computer screen slightly lower than your eyes: this will force you to close your eye lids a little.
• Make sure you blink! This prevents dry eyes and stops your cornea going cloudy – keeping your vision clear.