A surprising therapy is showing promise for chronic pain, vision loss, and muscle recovery, among other conditions.
It’s not a pill, an injection, or surgery.
It’s light.
Yes, light. The thing that appears when you open the curtains, flip a switch, or strike a match.
Light illuminates our world and helps us see. Early human trials suggest it may help us heal in new ways as well.
“Phototherapy is still in its infancy,” said Mohab Ibrahim, MD, PhD, a professor of anesthesiology at the University of Arizona, Tucson, who studies the effects of light on chronic pain. “There are so many questions, a lot of things we do not understand yet. But that’s where it gets interesting. What we can conclude is that different colors of light can influence different biological functions.”
This growing field goes by several names. Light therapy. Phototherapy. Photobiomodulation.
It leverages known effects of light on human health — such as skin exposure to ultraviolet light producing vitamin D or blue light’s power to regulate human body clocks — to take light as medicine in surprising new directions.
New Science, Old Idea
The science is young, but the concept of using light to restore health is thousands of years old.
Hippocrates prescribed sunbathing to patients at his medical center on the Greek island of Kos in 400 BC. Florence Nightingale promoted sunshine, along with fresh air, as prerequisites for recovery in hospitals during the Civil War. A Danish doctor, Niels Finsen, won the Nobel Prize in 1903 for developing ultraviolet lamps to treat a tuberculosis-related skin condition. And worried parents of the 1930s sat their babies in front of mercury arc lamps, bought at the drugstore, to discourage rickets.
Today, light therapy is widely used in medicine for newborn jaundice, psoriasis, and seasonal affective disorder and in light-activated treatments for cancers of the esophagus and lungs, as well as for actinic keratosis, a skin condition that can lead to cancer.
But researchers are finding that light may be capable of far more, particularly in conditions with few treatment options or where available drugs have unwanted side effects.
How Red Light Could Restore Vision
When 100 midlife and older adults, aged 53-91, with the dry form of age-related macular degeneration (AMD) were treated with an experimental red-light therapy or a sham therapy, the light treatment group showed signs of improved vision, as measured on a standard eye chart.
Volunteers received the therapy three times a week for 3-5 weeks, every 4 months for 2 years. By the study’s end, 67% of those treated with light could read an additional five letters on the chart, and 20% could read 10 or more. About 7% developed geographic atrophy — the most advanced, vision-threatening stage of dry AMD — compared with 24% in the sham group.
The study, called LIGHTSITE III, was conducted at 10 ophthalmology centers across the United States. The device they used — the Valeda Light Delivery System from medical device company LumiThera — is available in Europe and now being reviewed by the Food and Drug Administration (FDA).
courtesy LumiThera
LumiThera's Valeda Light Delivery System (which is CE Marked in the European Union and available in select countries in Latin America, but not cleared by the FDA) is being studied for the treatment of dry AMD and other ocular diseases.
Exposure to red light at the wavelengths used in the study likely revitalizes failing mitochondria — the power plants inside cells — so they produce more energy, the researchers say.
“This is the first therapy for dry AMD that’s actually shown a benefit in improving vision,” said study coauthor Richard Rosen, MD, chair of ophthalmology at the Icahn School of Medicine at Mount Sinai and chief of Retinal Services at the New York Eye and Ear Infirmary in New York City. “Supplements called AREDS can reduce progression, and in wet AMD we can improve vision loss with injections. But in dry AMD, none of the treatments studied in the past have improved it.”
AMD develops when the eyes can’t break down natural by-products, which glom together as clumps of protein called drusen. Drusen can lodge under the retina, eventually damaging tissue.
“Retinal epithelial cells, a single layer of cells that cares for the photoreceptors in the eyes, are there for life,” Dr. Rosen said. “They have a tremendous capacity to repair themselves, but things [such as aging and smoking] get in the way.”
“I’m proposing,” Dr. Rosen said, “that by boosting energy levels in cells [with red light], we’re improving normal repair mechanisms.”
Lab studies support this idea.
In a 2017 mouse study from the University College London Institute of Ophthalmology in England, retinal function improved by 25% in old mice exposed to red light. And a 2019 study from the Ophthalmological Research Foundation, Oviedo, Spain, found that exposure to blue light harmed the mitochondria in retina cells, while red light somewhat counteracted the losses.
If cleared by the FDA — which the company anticipated could happen in 2024 — LumiThera’s light delivery device will likely be most useful in the beginning stages of dry AMD, Dr. Rosen said. “I think treatment of early dry AMD will be huge.”
Eventually, light therapy may also be valuable in treating or managing glaucoma and diabetic retinopathy.
For now, Dr. Rosen recommended that clinicians and consumers with AMD skip over-the-counter (OTC) red-light therapy devices currently on the market.
“We don’t know what kind of light the devices produce,” he said. “The wavelengths can vary. The eyes are delicate. Experimenting on your own may be hazardous to your vision.”