New US research has found that blue light from digital devices such as smartphones and tablets can trigger a process in the retina of the eye which kills cells, and might increase the risk of blindness.

Led by Dr Ajith Karunarathne and a team of chemists at the University of Toledo, the new research investigated how blue light from digital devices affected sight.

They found that exposing the eye to blue light causes a reaction which leads an essential light-sensitive protein in the retina, known as retinal, to generate poisonous molecules in photoreceptor cells, resulting in their death.

"It's toxic. If you shine blue light on retinal, the retinal kills photoreceptor cells as the signaling molecule on the membrane dissolves," explained Kasun Ratnayake, a student researcher in Karunarathne's cellular photo chemistry group. "Photoreceptor cells do not regenerate in the eye. When they're dead, they're dead for good."

The process leads to age-related macular degeneration, or the death of photoreceptor cells in the retina. Macular degeneration is an incurable eye disease that results in significant vision loss. It's the leading cause of blindness in the United States and average onset is at 50 to 60 years.

Dr Karunarathne also exposed other types of cells to retinal molecules, including cancer cells, heart cells and neurons.

When exposed to blue light, these cell types also died as a result of the combination with retinal.

However, blue light on its own or retinal without blue light had no effect on cells.

"The retinal-generated toxicity by blue light is universal. It can kill any cell type," said Dr Karunarathne, "No activity is sparked with green, yellow or red light."

The team noted that a molecule called alpha tocoferol, a form of Vitamin E, a natural antioxidant found in the eye and body, can stop the cells from dying. But as we age, or if the immune system is suppressed, we lose the ability to fight against attacks by retinal and blue light.

"We are being exposed to blue light continuously, and the eye's cornea and lens cannot block or reflect it," Dr Karunarathne commented. "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."

The researchers are also investigating the light emitted from televisions as well as smartphones and tablet screens, to better understand how cells in the eyes are affected by everyday blue light exposure.

To protect your eyes from blue light, Karunarathne advises wearing sunglasses that can filter both UV and blue light outside, and to avoid looking at your cellphone or tablet in the dark.

The findings were published in Scientific Reports.