Computers and mobiles may have made life more convenient, but our eyes are taking the strain. Lisa Salmon reports on a very modern health hazard.
Growing up, most of us heard the words, 'You'll get square eyes', as we gazed a tad too keenly at the TV screen.
The warning may have been a little exaggerated, but it's not entirely unfounded. Spending hours staring at a screen won't give your eyes 90-degree angles, but it will put you at risk of eye strain, which experts warn is becoming more and more of a problem.
Looking at screens is now as much a part of modern life as driving a car or eating a ready meal - if not more so. Millions of office workers spend upwards of seven hours a day in front of a computer, and laptops and mobile phones have also increased screen use.
Steve Schallhorn, ophthalmic surgeon and chairman of Optical Express's International Medical Advisory Board, says: "Our dependence on and use of screen-based devices is set to increase even further with technological advances, and there's no doubt that daily and prolonged use of screens can have a detrimental impact on eyesight."
Schallhorn says the 'Net Generation' are the most at risk, pointing out that 63% of 18 to 24-year-olds recently surveyed admitted that they check their smartphone every 30 minutes, and often watch TV while simultaneously using a laptop, tablet, smartphone or computer.
It's not just teens who are guilty of multi-screening; 30% of UK adults who wear prescription glasses or contact lenses regularly do the same. And our screen habits are taking their toll on our eye health.
According to Optical Express, more than one in four adults (26%), 22% of 25 to 34-year-olds, and 17% of 18 to 24-year-olds, have visited an optician because their eyes felt tired from using a PC or watching TV or other screens.
If you use a computer regularly, chances are you've experienced eye strain. Common signs include red, bloodshot eyes, tired eyes and difficulty focusing, as well as headaches and soreness around the eyes.
Excessive screen use can also worsen dry eye problems which, in the worst cases, can even lead to scratches on the cornea and damaged vision.
While screen strain alone won't cause blindness, it is a real eye health issue.
Mr Bobby Qureshi, a consultant eye surgeon at The London Eye Hospital, says: "Strain from staring at a computer all day won't cause permanent damage but it will give you a bad headache.
"As well as straining, people blink around 25% less when they're looking at a screen, which worsens the effect."
Blinking is vital for keeping eyes moist, which is why people often end up with dry, gritty eyes after a long day at their desk.
Straining can also worsen symptoms of existing sight problems or weaknesses, as the muscles in and around the eyes are forced to overwork for prolonged periods, causing them to become fatigued.
This is particularly an issue for people who have one eye which is weaker than the other, or are short-sighted in one and long-sighted in the other.
Optomtetrist Dr Rob Hogan, a treasurer of The College of Optometrists, points out: "It's very rare to come across someone who has exactly the same focusing mechanism in each eye, but an imbalance can lead to headaches and eye strain, where people peer or screw their eyes up and may get aches around the eye."
Follow these tips for avoiding the strain...
Research by The College of Optometrists found that 86% of people value their eyesight above any other sense. Yet, millions either can't remember when they last visited an optometrist, or believe it's been more than 10 years since their last test.
The College of Optometrists recommends that adults have an eye test every two years unless advised otherwise, and children and the over 65s should be tested annually.
A test will pick up defects including short and long-sightedness and the need for reading glasses. Correcting these problems will mean you are able to focus more easily, thus reducing your likelihood of eye strain.
HAVE A BREAK
If you must spend a lot of time in front of a screen, make sure you take regular breaks. Leave your desk and go for a walk if you can - even if just to the kitchen - to allow your eyes to focus on distant objects and let the muscles relax.
When this isn't possible, Hogan also recommends that screen users follow the 20-20-20 rule: after 20 minutes of screen usage you look should look at something about 20ft away for 20 seconds, before resuming screen use.
At home, avoid the temptation of using a laptop and mobile while watching TV simultaneously, as this will force focusing mechanisms into overdrive.
Dry eyes can be extremely uncomfortable, and if left untreated may cause ongoing soreness and even damage to the delicate cornea in extreme cases.
The 20-20-20 rule and regular screen breaks will also help prevent dry eyes, as these periods away from the screen will encourage more blinking.
It's easy to fall into the habit of staring at a computer screen and losing track of time and forgetting to blink - even when discomfort kicks in!
If you feel your eyes becoming gritty and dry, ensure you take a break, allow your eyes to rest and remind yourself to blink, and try not to rub your eyes.
If dryness continues to be a problem, speak to an optician or optomestrist for advice. Drops may help keep eyes moist.