Can looking at a computer screen affect your vision?

Our eyes are our windows to the world. We use them for everything from reading and browsing the internet, to finding our way around and gazing at our loved ones.

But how much do you know about looking after these precious assets? Here we sort fiction from fact when it comes to taking care of your eyes.

Can looking at a computer screen affect your eyesight?

Verdict: Yes, looking at a computer screen a lot may increase your risk of short-sightedness.

Brisbane optometry professor Nathan Efron does not consider computer screens “harmful” to our eyes.

But he admits if you use one a lot, you increase your risk of becoming slightly more short-sighted – where your eyes focus well only on close objects while more distant objects appear blurred. This is especially the case for children and young adults, whose eyes are still developing.

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Before you switch off the computer, it’s worth noting that doing any close-up work – including reading – will have the same effect on your eyes.

Exactly why the risk increases isn’t well understood and two theories have been proposed. First, when we read up close, objects in the peripheral visual field are not perfectly focused, and the eye tries to grow slightly larger to correct this, making you a little more short-sighted. Second, it’s thought the constant contraction of eye muscles when we focus up close somehow makes the eyeball more elongated, which again tends to make you more short-sighted.

Do glasses weaken your eyes?

Verdict: No, your glasses won’t weaken your eyes.

If you think your eyesight’s become worse since you’ve started wearing glasses, you’re far from alone.

Struggling to focus on printed matter is an unfortunate sign of ageing. Changes to the lens of the eye as you get older mean you have to move the page further and further away before you can see properly. It’s called presbyopia and it strikes us all, usually by our mid 40s.

And the truth is many eye conditions, including presbyopia, get worse over time by themselves, specs or no specs.

In other words, it seems harder to read things without your glasses because it is. But it was going to happen anyway, and your glasses aren’t to blame.

What your specs have done is got you used to seeing more clearly. So when you take them off, the contrasting blurriness is more noticeable.

Should you avoid rubbing your eyes?

Verdict: Yes, in rare cases it can damage your vision.

For most people, an occasional gentle rub is nothing to worry about, says Professor Charles McMonnies, from the School of Optometry and Vision Science at the University of NSW.

But if you rub your eyes too hard, too often or over a long period of time, you could get into trouble, says McMonnies, a research optometrist with a special interest in eye rubbing. He says studies show that rubbing causes our eye pressure to spike.

Even a light rub doubles it, he says. Removing eye make-up or wiping away tears increases the pressure a little more. But scrunching up your eyes then using your knuckles to gouge really hard shoots up your eye pressure more than 20 times.

For most of us, our eye pressure returns to normal when we stop rubbing and the temporary blip does no obvious long-term damage. But for those with certain eye conditions, an increase in eye pressure caused by hard, frequent or prolonged rubbing could be more serious.

Hard eye rubbing can also damage the front of the eye. The combination of increased eye pressure and the mechanical damage caused by rubbing can harm the cornea, and in rare cases tear it. More commonly, it's weakened and pushes forward to become more conical, like the pointy end of a rugby ball, a condition known as keratoconus. Again, the damage could be enough to cause significant loss of sight.

Does reading in dim light damage your eyes?

Verdict: Not likely, but reading too much in general can affect your sight.

We've all been there – so engrossed in a good book you don't want to stop reading, despite poor light.

But this is unlikely to permanently damage your eyes, says Brisbane optometry professor Nathan Efron. It's true you'll probably find it more comfortable to read in good light, but there's no evidence low light causes any permanent harm.

The most likely outcome is temporary "eye strain" – a discomfort we attribute to our eyes, but which has no known physiological cause, Efron says.

"People will say they've got tired eyes, burning eyes, strained eyes. But the problem might not actually be in the eyes. It might be caused by the muscles around the eye, the brow and so on. We don't really know."

But any eye strain should disappear within a day or so (at most).

Do your sunnies need to have an SPF?

Verdict: Yes, it's important to have sunglasses that protect your eyes from damaging ultraviolet radition.

Like your skin, your eyes are susceptible to both short term and long term effects of harmful ultraviolet (UV) radiation, says Cancer Council Australia's Skin Cancer Committee chair Louise Baldwin.

"The most common short-term impact of UV exposure to the eye is acute photo keratopathy, which is like sunburn of the cornea and can cause inflammation," she explains.

"Long-term exposure to UV radiation can result in more serious damage to the eyes, including squamous cell cancers on the surface of the eye and skin cancer around the eyes. It can also cause cataracts, damage to the retina and climatic droplet keratopathy (cloudiness of the cornea)."

When it comes to choosing sunnies that are going to best protect your eyes, what matters is the UV radiation-absorbing properties of the plastic material used in the lenses of a pair of sunglass.

"Of the five categories of lenses (0-4) it's best to pick a pair with a rating of 2 or above to guarantee sufficient UV protection," she says.

Do kids need to wear sunglasses?

Verdict: Yes, children also need to protect their eyes from sun damage.

We're told we should always make sure our kids are wearing a shirt, hat and sunscreen before they go outside. But do they really need to slide on shades as well?

Dr Michael Jones, paediatric eye specialist at the Children's Hospital at Westmead and the Sydney Eye Hospital, says kids definitely need to wear sunglasses while they are outside.

In fact, wearing sunglasses as a youngster can help protect against the most common eye conditions that develop later in life.

We tend to forget that a lot of our sun exposure happens when we are children, when we spend a lot of time outdoors in direct sunlight, Jones says.

UV light from the sun is a form of radiation and it can damage cells in the eye.

While there's no evidence that children's eyes are more susceptible to UV light than adults', the longer eyes are exposed to these harmful rays without protection, the more damage they accumulate.

Read more: Do kids need to wear sunglasses?

This post originally appeared on the ABC and was republished here with full permission. 

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