Blue light from phones might ruin your eyesight - study

Tablets and phones are already in parents' bad books for keeping the kids up at night - and now they might be on optometrists' naughty lists too.

New research has found the blue light they emit can kill photoreceptor cells in the eye, leading to age-related macular degeneration - the most common cause of blindness in New Zealand.

"We are being exposed to blue light continuously, and the eye's cornea and lens cannot block or reflect it," said study leader Dr Ajith Karunarathne at the University of Toledo.

Exposure to blue light causes molecules called retinal, found in the retina, to create "poisonous" chemical molecules in photoreceptor cells.

"It's toxic - if you shine blue light on retinal, the retinal kills photoreceptor cells as the signalling molecule on the membrane dissolves," said Kasun Ratnayake, a member of Dr Karunarathne's team.

"Photoreceptor cells do not regenerate in the eye. When they're dead, they're dead for good."

Tests showed retinal was able to kill any cell in the human body if it was exposed to blue light.

"No activity is sparked with green, yellow or red light," said Dr Karunarathne.

The researchers also found how to stop it - with a molecule called alpha tocoferol, which the body produces, but with less efficiency as we age.

"The lab currently is measuring light coming from television, cellphone and tablet screens to get a better understanding of how the cells in the eyes respond to everyday blue light exposure," said Dr Karunarathne.

Blue light in recent years has been shown to suppress melatonin production. Photo credit: Getty

Significant vision loss to macular degeneration usually begins when people are in their 50s and 60s, but there are fears the widespread use of electronic devices - particularly into the evenings when people would not normally be exposed to so much blue light - could see people's vision deteriorate at younger ages.

"Some cellphone companies are adding blue-light filters to the screens, and I think that is a good idea," said Dr John Payton of the University of Toledo's chemistry department.

The latest versions of Apple's iOS and Microsoft's Windows both have blue light filters built-in, and can be set to turn on and off in sync with the sun. Some Android manufacturers such as Google have built it into their phones, and there are several apps available in the Play Store for those whose phones don't.

Dr Karunarathne says it pays to wear UV- and blue light-blocking sunglasses when you're outside on a sunny day, and avoid staring at your phone at night - especially if it doesn't have a blue-light filter.

"By learning more about the mechanisms of blindness in search of a method to intercept toxic reactions caused by the combination of retinal and blue light, we hope to find a way to protect the vision of children growing up in a high-tech world."

Blue light in recent years has been shown to suppress melatonin production, making it more difficult to sleep at night but improving mood and alertness during the day.