Pain Management Gets the Green Light
About 20% of American adults have chronic pain caused by migraines, headaches, fibromyalgia, arthritis, and the pain that can remain after recovering from an illness or injury.
Treating chronic pain with physical therapy or cognitive behavior therapy can be time-consuming. The results aren’t always predictable or long-lasting. A mainstay of treatment for chronic and acute pain in the United States is opioids, which 11.5 million people say they misuse. Addiction to the prescription pills has skyrocketed.
But new research by Padma Gulur, MD, a professor of anesthesiology and population health at Duke University School of Medicine, has bolstered a bright idea about pain management: green light exposure.
The idea is young, and benefits are far from conclusive, but her work, and that of a handful of others, has revealed the potential of green light exposure as an affordable treatment with few side effects or risk of addiction.
Gulur’s research team studied 34 fibromyalgia patients who were randomized to wear various shades of eyeglasses four hours a day for two weeks: 10 patients wore blue eyeglasses, 12 wore clear eyeglasses, and 12 wore green eyeglasses.
Patients who wore green eyeglasses were the only group with a majority of subjects having a decline in anxiety scores, and there was a statistically significant difference in the fear question in particular.
“We found that although their pain scores remained the same, those who wore the green eyeglasses showed higher odds of a 10% decline in opioid use, demonstrating that their pain was adequately controlled,” Gulur said of study results.
Gulur presented her findings this fall at a conference for the American Society of Anesthesiologists. The response grew beyond those who heard her talk that day. Patients and clinicians from around the world wanted to know more.
“It’s been overwhelming, quite honestly,” she said. “There’s been an outpouring internationally of those asking for more information. Obviously, there is a huge patient population that is very excited at the opportunity to have something they
can do for themselves to help with their pain, that is not invasive and will not leave them with a lot of side effects.”
Lighting the way to solutions
Researchers used commercially available green eyeglasses. Even though they looked the same, each was tested with a spectrometer before and after the study to determine which wavelength of green light each produced.
“What stood out for us was almost all the patients who got green glasses in the randomization didn't want to give them back,” Gulur said.
The green wavelength ranges from 495 to 570 or so, she explained. Rather than the middle, or peak, “the wavelengths that were helping folks were on either end of that spectrum.”
“Some people responded to much lower wavelengths, between the 490s to 510s, and the others responded to the higher wavelengths,” she said.
While the study of green light for pain management has recently picked up among basic scientists and clinicians, light is known to impact wound healing, mood, and circadian rhythm. Most people feel sleepy when it’s dark.
The ability of green light to impact pain may be rooted in why being in nature feels so good. But scientists hope to get more precise in understanding the power of green.
“If you were to ask me, I’d think it would be blue,” Gulur said. “When we see the ocean and its shades of blue and turquoise, it’s calming. It feels good to see that. Color impacts our life and mood immensely.”
Gulur joined the faculty at Duke Health after treating patients for pain at Harvard University’s Massachusetts General Hospital. In her nearly seven years at Duke, her work in patient care has evolved to include leadership roles as executive vice chair of Duke Anesthesiology and director of Pain Management and Opioid Surveillance for Duke Health.
“Treating pain for decades and the lack of non-invasive easily incorporated solutions drove me to study this,” she said.
Clues about green light and pain can be found in the cones and rods — the eye cells that sense light — that send electrical signals from the eye to the brain. Gulur and others want to know more about how these pain circuits in the brain respond to visual inputs.
She lists a growing roster of parameters to explore that will build on the much-watched findings she presented earlier this year from the Duke research team, which included Duke biostatistician Mary Cooter and postdoctoral researcher Amanda Nelli.
Larger studies that assess green light exposure on different chronic pain conditions are in store. There’s also interest in the dose effect, narrowing down which wavelengths are the most effective so shorter exposures may be beneficial.
“Even more importantly we want to learn the mechanism,” Gulur said. “What’s doing this? So we’re planning some FMRI studies to try and understand what lights up (in the brain) when people are exposed to green light and get pain relief. There’s a lot more to be done, and we’re very excited about it.”
Given the challenge that patients are facing, she’s motivated to find treatments that can easily be incorporated into their daily lives that offer pain relief.
“We recognize that green light as a visually mediated analgesic is not the only answer,” Gulur said. “We think of pain management as multi-modal – often requiring more than one method. For some patients we’ve found green light exposure is enough. They start to feel better just with this. But for others it may help them stay within the therapeutic index for other drugs or pharmacology they are taking. Even as an adjunct, this could be huge.”
Shantell M. Kirkendoll is a senior science writer and editor for the School of Medicine’s Office of Strategic Communications.
Photos by Jim Rogalski
Main image: Padma Gulur, MD, is a professor of anesthesiology and population health at Duke University School of Medicine who studies pain management.
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