Thursday 8 January 2015

Screens and eyes

For as long as we’ve had televisions they have been accused of damaging our eyes – but now, with screens everywhere, what’s the true picture?

When I was young, older people were always telling us not to sit too close to the TV or to spend too much time watching it. Yet back then, we only had a fraction of the screen time that most of us experience today. You may well spend all day at work looking at a computer screen, then come home to spend the evening in front of the TV. And what were you doing in between these times? Looking at your phone or tablet.

In 2014 there was a scare story that overusing smartphones may damage the eyes. The concern was that the light from LED screens contains more blue/violet light than the natural light that best suits our eyes, and the higher energy blue/violet light can overload the sensors on the retina, increasing the risk of macular degeneration, a common cause of blindness.

The story particularly highlighted the risks from smartphone use, where the screen is held considerably closer to the eyes than a computer or TV screen and is often used in lower lighting condi- tions, where the dilated irises of our eyes allow more light in.

We have to approach this story with a little caution. There is no study showing that exposure to screens, even smartphones, causes eye problems – this is extrapolating from laboratory-based evidence that light in this region can cause damage to the type of cells used in the retina. So at the very most, this is a precautionary warning as yet.

What is certainly true is that our eyes don’t respond well to being focused as closely as a smartphone requires (TVs are usually positioned at a better distance) for long periods of time, and this can cause eye strain. Taking a break from screens for at least five minutes in each hour, and a few longer breaks during the day is highly recommended. Furthermore, regular screen users – which is pretty well all of us – should have regular check-ups with an optician.

UPDATE: In December 2014 a different study showed that people who read backlit screens in before going to sleep produced less of the hormone melatonin. This can make it harder to get to sleep, and in the long term, sleep deficiency can produce significant health problems. As yet the evidence is relatively limited - this was a very small study with just six people on each kind of book. However if you do have trouble getting to sleep, and you read from a screen for your bedtime reading it is worth switching to a paper book (or an e-ink reader like a basic Kindle that doesn't have a backlight) to see if it helps make sleep more easy. Ideally avoid close backlit screens (including phones and computers as well as tablets and backlit e-readers) for a couple of hours before trying to sleep. TVs don't seem to be a problem as we don't sit anywhere near as close, so the blue backlight is a relatively small part of our incoming light - and the generally darker coloured picture of video is better than the stark white of a page to read. If you have to use a backlit e-reader, try turning down the brightness.

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