In today's highly connected world we are increasingly having blue light beamed into our eyes at all times of day. While a convincing body of research is suggesting blue light from our TVs, computers, smart phones and tablets can significantly disrupt our circadian rhythms, it is less clear how much damage this particular spectrum of light is causing to our eyes. A new study from the University of Toledo has homed in on exactly how blue light can damage our eyes and the researchers recommend avoiding looking at cell phones and tablets in the dark.

"We are being exposed to blue light continuously, and the eye's cornea and lens cannot block or reflect it," says Ajith Karunarathne, one of the researchers on the new study.

Our vision fundamentally relies on a molecule called retinal to sense light, and effectively signal visual information to the brain. Karunarathne explains, "You need a continuous supply of retinal molecules if you want to see. Photoreceptors are useless without retinal, which is produced in the eye." The new study finds that in the presence of blue light, retinal can turn against the body, generating chemicals that destroy photoreceptor cells.

"It's toxic. If you shine blue light on retinal, the retinal kills photoreceptor cells as the signaling molecule on the membrane dissolves," says Kasun Ratnayake, another researcher working on the project. "Photoreceptor cells do not regenerate in the eye. When they're dead, they're dead for good."

It was found that age-related macular degeneration occurs when the immune system slowly becomes less able to protect against the effects of this combination of retinal and blue light. A natural antioxidant called alpha tocopherol, a derivative of vitamin E, was also found to protect against this degenerative process. Interestingly, the researchers noted that other visible spectrums of light, such as green, yellow or red, did not trigger the same retinal toxicity as blue light.

It's unclear what implications the discovery of the process actually are for those that frequently use screen-based devices. The next step for the researchers will be to closely measure the levels of blue light that come from objects such as cell phones and tablets, to help understand how our eyes are directly responding to exposure from those sources.

"If you look at the amount of light coming out of your cell phone, it's not great but it seems tolerable," says John Payton, who also worked on the study. "Some cell phone companies are adding blue-light filters to the screens, and I think that is a good idea."

Perhaps the more explicit outcome of the study is a better insight into how age-related macular degeneration occurs. Our eyes are exposed to blue light extensively over our lifetimes not just from screen devices but also from ever-present sunlight. This newly discovered mechanism suggests the degenerative process resulting from the combination of retinal and blue light may be implicated in a more long-term, and slower, degradation of our eyesight. This is not something that happens quickly, but instead is a more gradual process, that is potentially amplified by adding our increasing use of screen-based devices to the mix.

The new research was published in the journal Scientific Reports.

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