Eyeworld

22 March 2019 EW NEWS & OPINION Research highlight by Maxine Lipner EyeWorld Senior Contributing Writer recently scientists had little idea why. A study 1 published in Scientific Reports indicates what may hap- pen to photoreceptor cells in the presence of blue light, according to Ajith Karunarathne, PhD, assistant professor, biochemistry department, University of Toledo, Ohio. New insight into how blue light may damage eyes W hile it's well known that blue light can damage vision and lead to macular degeneration, until Honing in on device screens Graduate students working in Dr. Karunarathne's lab Kasun Ratnayake (left), Dr. Karunarathne (middle), and Dr. John Payton (right) work on a blue light exposure experiment. Source (all): Ajith Karunarathne, PhD Initially, investigators in Dr. Karunarathne's lab were focused on engineering photoreceptors and inserting them in cancer and other types of cells, he explained, adding that one of the things that they needed to do was introduce a molecule known as retinal into cells. Although those cells had nothing to do with vision, "we found that when we exposed these cells to blue light they die," Dr. Karunarathne said. "So then we introduced retinal without having any photoreceptors in these cells and exposed the cells to blue light." Once again, the cells died. However, when exposed to other colors of light, this did not oc- cur. "Also, when we exposed cells to just blue light without retinal, noth- ing happened," Dr. Karunarathne said. Investigators started examining how this process might work in a similar situation in the eye. "We can reflect or completely eliminate UV light entering the eye, but the human eye is transparent to blue light, so blue light gets in," he said, adding that this gets focused on the retina. Meanwhile, the retinal, which is a vitamin derivative, is continuously produced by the eye. Reactive oxygen concerns "We started investigating and found that the retinal absorbs blue light," Dr. Karunarathne said. "Then, this molecule goes to a high-energy state and the high-energy state can deliv- er that high energy into oxygen." The eye itself is well oxygenated, and the transfer of the energy makes the oxygen toxic and becomes what is known as a reactive oxygen spe- cies, Dr. Karunarathne said. Hydro- gen peroxide is one of the reactive oxygen species, and when you place a drop on the skin, you can see bub- bles as it reacts. As part of their work, investiga- tors found that when they exposed cultured cells to blue light the retinal molecule ended up attacking important biomolecules needed for cell survival, likely by generating reactive oxygen species. "If you expose them to retinal and blue light long enough, cells die," Dr. Karunarathne said. Investigators also discovered that alpha tocopherol, a molecule derived from vitamin E, can pre- vent this cell death. "We found that alpha tocopherol can quench and neutralize these toxic reactions and prevent the damage to cells," Dr. Karunarathne said. While it is unknown wheth- er blue light from devices such as smartphones and computers is intense enough to induce this type of toxic reaction in the eye, some scientific literature suggests that blue light induces vision damage. "We wonder if the previously report- ed blue light-induced vision damage is from the same set of reactions that we observed," Dr. Karunarathne wondered. "We don't know yet and we are looking into that." Role for vitamin E In addition, they are also investi- gating the potential role of vitamin E. "We think this specific molecule from vitamin E is a natural antioxi- dant and alpha tocopherol is, too," Dr. Karunarathne said. "We think this is going into the same location in the cell where retinal accumu- lates, so this can directly take up those reactive species and neutralize them." Practically speaking, while Dr. Karunarathne understands concerns that the public has about blue light emanating from current technology, he stressed that it remains un- known what effect these truly have. Although retinal is known to be in the eye, it is unknown how much free retinal is available to induce this toxic reaction. "I think the hu- man body is very resilient; we have natural antioxidant machinery," Dr. Karunarathne said. However, in cases where people have problems with the retinal clearance mecha- nism, they may be more vulnerable to damage by blue light. "In general, I'm not too worried that the light from mobile devic- es can induce substantial vision damage," he said. "I use my mobile phone and computer every day and I'm not wearing any glasses at this point because I want to see what the upcoming experiments tell us." EW Reference 1. Ratnayake K, et al. Blue light excited retinal intercepts cellular signaling. Sci Rep. 2018;8:10207. Editors' note: Dr. Karunarathne has no financial interests related to his comments. Contact information Karunarathne: Ajith.Karunarathne@UToledo.edu

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