Blue light, typically associated with the screens of our electronic devices, is a known sleep inhibitor, and we've suspected that it's bad for our eyes.
And now, thanks to a study published in Scientific Reports, we can confirm that suspicion. This harm could lead to age-related macular degeneration, a leading cause of blindness in the United States.
"It's no secret that blue light harms our vision by damaging the eye's retina. Our experiments explain how this happens," Ajith Karunarathne, assistant professor in the University of Toledo's department of chemistry and biochemistry and one of the study's authors, said in a statement.
How the damage is done
We see thanks to a collection of eye parts that help to gather and send information to the brain. Light passes through the cornea, a clear, dome-like structure over the eye. The cornea bends light and our irises, the colored part of eyes, regulates the pupil, which widens or narrows to control the amount of the light passing through. Once the light has gone through the pupil, it passes through to the lens. The lens focuses the image a bit more onto the retina.
The retina is photosensitive tissue that contains photoreceptor cells. These cells help convert light into electric signals that then travel along the optic nerve to the brain, where the information is processed by the visual cortex. Without the retina and its photoreceptor cells, the visual information we take in through our eyes wouldn't trigger a biochemical response that activates the brain to process that information. The retina is able to do what it does thanks to retinal molecules. Retinal, a form of vitamin A, converts light into those electric signals that travel to the brain.
This is where the study from the University of Toledo researchers comes into play.
"You need a continuous supply of retinal molecules if you want to see," Karunarathne said. "Photoreceptors are useless without retinal, which is produced in the eye."
Researchers exposed retinal to blue, red, yellow and green lights. When researchers exposed the retinal to blue light, it triggered a reaction in which the retinal releases reactive oxygen species (ROS), poisonous chemical molecules that killed 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," Kasun Ratnayake, a Ph.D. student researcher working in Karunarathne's cellular photo chemistry group, said in the statement. "Photoreceptor cells do not regenerate in the eye. When they're dead, they're dead for good."
The researchers repeated the process by exposing retinal to other cell cultures, including cancer cells, heart cells and neurons. When the cells mixed with retinal were exposed to blue light, they died. If they had retinal and were not exposed to blue light, the cells were fine; if they were just exposed to blue light without any added retinal, they were also fine.
"No activity is sparked with green, yellow or red light," Karunarathne said. "The retinal-generated toxicity by blue light is universal. It can kill any cell type."
Retinal isn't limited to traveling in the eye. It can be present throughout the body, which indicates that the toxicity could potentially be more widespread.
How to save your eyes
Age-related macular degeneration is the breakdown of the macula, the part of the retina that's responsible for central vision. It helps you to recognize faces and read. It typically affects people once they hit their 50s or 60s.
If retinal is killing off photoreceptors after being excited by blue light, then the degeneration might be sped up, particularly for older folks. The researchers found that alpha tocopherol, a vitamin E derivative and a natural antioxidant in the eye and body, can help stop the photoreceptor cells from dying. However, this process slows down as we age and our immune system weakens.
"That is when the real damage occurs," Karunarathne said.
To protect your eyes, the researchers recommend what's been recommended for a few years now: Avoid using screens in dark spaces and wear sunglasses that filter out UV and blue light. In the meantime, the researchers are measuring how much blue light comes from our phones, tablets and TV screens to better understand how our eyes deal with so much blue light exposure.
"Every year more than two million new cases of age-related macular degeneration are reported in the United States," Karunarathne said. "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."