Too much screen use is taking its toll on young people's eyes, with children as young as five having to get treatment, Canterbury optometrists say.
Many patients had dry eyes, eyestrain or headaches, they said.
Nine out of 10 New Zealand optometrists had concerns about the number of people they saw with eye damage linked to heavy use of digital devices, a survey by Eyezen lenses this month found.
Rangiora Eyecare optometrist Kimberley Shea said she saw several patients a day who complained of problems linked with screen use, and other optometrists she worked with reported the same.
She was concerned by the number of children and teenagers who were having problems with their eyes.
"Kids are learning on tablets right from when they are learning the alphabet. It is too early to know if there is a direct correlation with screen time and these issues, but until we do we need to be careful," Ms Shea (left) said
She said it was very hard to diagnose eye conditions in young children.
"If things are blurry they won't realise it's anything out of the ordinary, they would just think it's just how it's meant to be," she said.
Working with screens was often unavoidable for people, but there were simple things they could do to minimise the risk of hurting their eyes, she said.
NZ Association of Optometrists national director Lesley Frederikson said most people were aware of the damage ultra violet light could do to their eyes, but not that exposure to blue-violet light had also been linked to retina damage.
Even when using screens set to maximum brightness, the amount of light emitted should not be enough to damage your eyes, studies have found.
But staring at a screen for a long time without a break could cause problems.
"The main issue is that people are not well adapted to staring directly at a close stimulus for long periods and often fail to blink enough while staring at the screen," Dr Frederikson said.
Ways to protect your eyes from damage when using screens
•Try to look away from your screen at least every 20 minutes, and focus your eyes on something far away for at least 20 seconds to relax the muscles in your eyes. Try to take a short break from the screen every hour.
•When concentrating on a screen most people blink only about a third as often as they usually would, meaning your eyes dry out. Make a conscious effort to blink more.
•Your screen should be about as bright as your surroundings. If it is too bright or too dark it could strain your eyes.
•Blue-toned light causes more strain to your eyes than orange or red-toned light. You can change the colour temperature of your display on some devices, download apps which will do it for you, or buy specialist glasses which filter out the light.