Blue light can have a worrying effect on our eyes, literally killing the cells in our retinas. Now, researchers from the University of Toledo have discovered exactly why this is, publishing their findings in the journal Scientific Reports.

“We are being exposed to blue light continuously, and the eye’s cornea and lens cannot block or reflect it,” study author Dr Ajith Karunarathne said in a statement. “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, sometimes referred to as age-related macular degeneration or AMD, is a condition that results from the breakdown or thinning of cells in the macula – a part of the eye’s retina that’s important for seeing fine details. The light-receptive cells in the macula of those with AMD die off, leading to serious vision problems.

Unfortunately, there’s currently no cure for AMD, although certain treatments like eye injections can help slow down its progression. The disease tends to occur in middle to old age and is responsible for roughly half of cases of impaired vision.  

So where does blue light come in?

Well, it’s all to do with a molecule called retinal, which helps cells in the retina to sense light and relay visual information to the brain. When exposed to blue light, retinal turns on the eye, killing vital light-sensing cells. This is because the blue light causes it to trigger a series of reactions – a molecule in the affected cell’s membrane distorts, then an increase in calcium changes its shape, and the cell dies. The damage is permanent.

“Photoreceptor cells do not regenerate in the eye. When they’re dead, they’re dead for good,” said Karunarathne.

The researchers found that when retinal was present, blue light also killed other body cells like cancer cells, heart cells, and nerve cells. “The retinal-generated toxicity by blue light is universal. It can kill any cell type,” Karunarathne said. The team didn’t find any evidence of the change when cells were exposed to other light wavelengths. 

The team also found a substance the body uses to stop cells from dying in this way. It is a derivative of vitamin E known as alpha-tocopherol, which is a natural antioxidant. However, as we get older, or if our immune system is compromised, it gets harder and harder for the cells that need this molecule to take it in efficiently.

The researchers note that our obsession with technology is also problematic. The Sun naturally produces a lot of blue light, as do the screens of laptops, smartphones, tablets, and TVs. The issue is that we stare into these screens at close proximity for many hours during the day and night. The researchers are currently looking into how this exposure might be damaging the cells in our eyes. 

“Some cell phone companies are adding blue-light filters to the screens, and I think that is a good idea,” study author Dr John Payton said.

As for macular degeneration, the researchers hope their findings could help to find a way to slow down the progression of this unpleasant disease.