A new study has illuminated one possible underlying mechanism by which blue light can damage retinal cells.

Kasun Ratnayake, MS, a PhD student from the University of Toledo in Ohio, and colleagues found that retinal cells are sensitive to blue light because they contain a protein called retinal. Blue light excites the retinal protein, which then irreversibly alters a signaling protein in the cell membrane. The distorted membrane-bound signaling protein, in turn, causes an increase in intracellular calcium, excessive cellular shape change, and ultimately cell death.

The researchers examined the effect of other wavelengths of light on the cells in culture, but found that only blue and ultraviolet light caused damage to cells. Ratnayake and colleagues published their results July 5 in Scientific Reports.

The authors emphasize that the findings do not suggest that light from digital devices causes similar damage to vision or possible blindness in humans. Rather, their study evaluated the effect of blue light on one type of experimental cell derived from the eye and did not directly measure potential damage to the human retina caused by blue light. In addition, the intensity of the light used in their experiments may not necessarily be the same as the light emitted from devices such as computers and smart phones.

“Whether blue light from mobile devices and digital screens induces similar toxicity levels is an unanswered question and is currently under investigation,” senior author Ajith Karunarathne, PhD, an assistant professor of chemistry and biochemistry at the University of Toledo, told Medscape Medical News in an email.

“Even if such a scenario is found, since the studies are done in cultured cells, that would not indicate that these devices can cause similar damages to the vision. Nevertheless, some literature suggests that removal of the blue component from intense light can reduce vision damage,” he added.

Both the cornea and lens of the human eye are transparent to blue light, which means theoretically that blue light can reach the retina, but how these results translate to humans is not straightforward, agreed Joshua Dunaief, MD, PhD, Adele Niessen Professor of Ophthalmology at the University of Pennsylvania in Philadelphia. Although Dunaief’s laboratory group has done research on the damaging effects of blue light, he was not involved in this study.

Other evidence supports the idea that light can damage the retina, and that blue light may be the most damaging wavelength. For example, previous experiments in laboratory cell lines have suggested that exposure to blue light may damage cells in the retina. Moreover, studies in mice have found that changes to the retinal protein caused by exposure to intense light can lead to age-related macular degeneration, retinopathy, night blindness, and other retinal disorders.

“The state of the field of blue light toxicity suggests that there may be some risk [from regular exposure to lower levels of blue light emitted by computer or smartphone screens,] but it’s not certain whether there is,” Dunaief said. “It’s very hard to determine whether levels of light that people are typically exposed to are causing damage.”

People have several options if they are concerned and want to protect themselves from possible risk caused by exposure to blue light.

“Ophthalmologists generally recommend that people should wear sunglasses when out in bright light, especially when at the beach or out on the water, and especially if they are at risk for macular degeneration because of family history,” Dunaief said.

Sunglasses should be dark gray or brown, which will block blue light and other wavelengths that can get to the retina. Although ultraviolet light is blocked by the cornea and lens and can’t reach the retina, ultraviolet light can increase the risk for cataracts, so it’s also a good idea to wear ultraviolet-blocking sunglasses.

Other options include the use of blue light filters in front of computer screens. Computer software called Flux also exists that can allow users to adjust the colors emitted by their screens away from the blue spectrum and toward the red and green spectrum.

Blue light also sets circadian rhythms, and exposure to it late at night may interfere with sleep, Dunaief cautioned. So it’s best to avoid looking at computers or smartphone screens before bedtime.

The authors and Dunaief have disclosed no relevant financial interests.

Sci Rep. 2018;8:10207. Full text