Why blue light from smartphones speeds up blindness

Scientists have discovered how blue light from screens on devices such as laptops and smartphones causes blindness, they say.

Prolonged exposure to the short-wavelength light triggers toxic molecules to be generated in the eye's light-sensitive cells that causes macular degeneration, a condition which may result in blurred or no vision in the centre of the visual field, according to research by the University of Toledo in the state of Ohio in the US.

Dr Ajith Karunarathne, an assistant professor in the university's Department of Chemistry and Biochemistry, said: "We are being exposed to blue light continuously and the eye's cornea and lens cannot block or reflect it.

"It's no secret that blue light harms our vision by damaging the eye's retina.

"Our experiments explain how this happens, and we hope this leads to therapies that slow macular degeneration, such as a new kind of eye drop."

Macular degeneration is an age-related condition that is common among people in their 50s and older.

Although it does not cause total blindness, it can make everyday activities such as reading and recognising faces difficult.

The condition is caused by the death of light sensitive cells in the retina. These cells need molecules called retinal, a form of vitamin E, to sense light and trigger signalling to the brain, enabling people to see.

But exposure blue light causes retinal to set a chain of reactions that leads to poisonous chemical molecules to be created in the light receptive cells, the research published in the journal Scientific Reports found.

Kasun Ratnayake, a PhD student at the University of Toledo who was involved in the study, said: "If you shine blue light on retinal, the retinal kills photoreceptor cells as the signalling molecule on the membrane dissolves.

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

The scientists found that a molecule called alpha tocopherol, a natural antioxidant found in the eye and body, stops the cells from dying but fails to offer any protection to the ageing population or those whose immune systems have been suppressed.

Dr Karunarathne said: "That is when the real damage occurs."

For those wanting to protect their eyes from blue light, Dr Karunarathne advises wearing sunglasses that can filter both UV and blue light outside and avoiding browsing on mobile phones or tablets in the dark.

Additional reporting by Press Association