Picture this, you have a splitting migraine. But rather than reaching for a bottle of pain medication and switching off the lights, you ditch the pills and turn on a special set of green LEDs instead. Basking in a green glow, you find your pain disappearing. Before long, you are good to go.
It may sound too good to be true, but a growing body of research points to the efficacy of low-level light therapy (photobiomodulation) as a non-invasive pain management treatment. Future therapies for everything from wounds to chronic pain, even tinnitus, are being explored using light therapy.
The idea of using light to heal dates back millennia— forms of light therapy were practised by Egyptians and Indians. In the 19th century, Florence Nightingale dubbed the importance of light for the sick “second only to their need of fresh air”. But the modern resurgence of the field began in 1960 with the work of Danish Nobel Laureate Niels Ryberg Finsen.
Finsen, considered the founder of phototherapy and winner of the 1903 Nobel Prize in Medicine, produced the first treatment of lupus vulgaris using concentrated light rays filtered through coloured pieces of glass. While Finsen’s therapy seemed to work, the exact mechanism remained unclear for decades. But new research is shedding light on why, with more studies exploring how certain wavelengths can be effective treatments for some conditions. The introduction of photochemotherapy in 1974 marked the beginning of an upsurge of interest in the field.
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“Low-level light therapy has been used in clinical practice for decades primarily in Asia and Europe. It has gained more popularity in the recent years as more instruments have become available and been accepted among regulatory bodies,” says Dr G Arun Maiya, Dean, Manipal College of Health Professions.
Dr Maiya says photobiomodulation (PBM) can be a simple, effective and cost-effective treatment for both acute and chronic pain. Today, PBM is performed not just by doctors but also through home-use PBM devices for everything from pain to wound-healing.
How photobiomodulation works
As Dr Maiya explains, PBM, also known as low-level laser therapy, operates through non-ionising light sources in the visible and near-infrared spectra, like LEDs and low-intensity lasers. It is based on the concept of low-energy bio-stimulation, inducing photochemical reactions in cells and tissues. PBM triggers several biological responses, such as pain relief, inflammation modulation, endorphin release, and increased ATP production, ultimately promoting tissue healing and restoring health.
What makes PBM interesting is how it intersects with our current avenues of treating pain. The human brain processes pain through a complex network of nerves, receptors, and pathways. Pain receptors, called nociceptors, are located throughout the body, and respond to injury or damage by sending signals to the spinal cord and brain. These signals are then processed by different areas of the brain, including the dorsal raphe nucleus (DRN) which modulates pain, resulting in the perception of pain.
A recent study titled Pain Relief Gets The Green Light published in the Science Transnational Medicine, looked at how green light, the most commonly used wavelength in PBM, worked to reduce pain in rodent models. It found a crucial role in the rod and cone photoreceptors in the eyes, as these in turn activate neurons in the ventrolateral geniculate nucleus (vLGN), and then convey the light signals to the DRN. The result is a less severe pain sensation.
PBM can impact a range of pathways that affect how we perceive pain, depending on the type of wavelength used and the nature of its action.
“There are discrete pathways for each of the reported PBM biological responses namely relieving pain or inflammation, modulating the immune system and promoting tissue healing and regeneration,” explains Dr Praveen R Arany, Associate Professor of Oral Biology at the University at Buffalo School of Dental Medicine and an expert on the therapeutic use of lasers and light.
Using light to relieve pain has long been seen even outside the clinic. The Japanese practice of “forest bathing” may even be an adjunct approach to using green light therapy, courtesy the diffused colour of sunlight.
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But asides from pain management, PBM has also been explored in wound healing.
“PBM promotes angiogenesis which is a formation of new blood vessels that helps in delivering more oxygen and nutrients to tissues thereby helping in pain relief and tissue healing. Along with angiogenesis, PBM helps in modulation of inflammation, increases release of endorphins, decreases oxidative stress, and increases ATP production within mitochondria restoring normative health of cells,” notes Dr Maiya.
Photobiomodulation therapies are being explored around the world. In September, the United States Army’s medical research wing announced a $2.4 million grant to investigate how effective green light therapy was for postsurgical pain and inflammation. Similar Army-funded research has looked at the potential of PBM in treating traumatic brain injuries as well as neurodegenerative disorders like Alzheimer’s and Parkinson’s.
Against the backdrop of a growing opioid crisis, light-based therapies are poised to offer an alternative to potentially addictive pain management treatments.
Present and future avenues
“There is unequivocally demonstrated benefits in supportive cancer care – PBM is now recommended to all cancer patients prior to their cancer treatment to reduce treatment-complications and improve quality of life and ultimate outcomes,” says Dr Arany.
Low-level light therapies do not destroy cells but rather promote energy production, cellular signalling and latent growth factors. As such, they are being explored to treat a range of conditions from tinnitus to cognitive health conditions as well as chronic pain.
“Neuropathic pain and diabetic foot ulcer, chronic pain and tissue healing requires multidisciplinary approach and PBM will be one of the promising treatment modalities in the coming years,” notes Dr Maiya. Dr Arany says areas where PBM could find wider acceptance include age-related macular degeneration arthritis, neck and back pain, wound healing, depression, sleep disorders, and neuromuscular-cognitive performance.
High-intensity light in the form of lasers is already deployed as a surgical tool, while low-level light therapies are performed everywhere from the clinic to one’s own home. The at-home use of light therapy mostly revolves around the use of green and red LED lamps, depending on the desired wavelength.
However, as Dr Arany notes, one of the most common myths about PBM is the perceived ease of doing it as a treatment. “Most folks are using a point-n-shoot approach, hoping for a therapeutic outcome. This is incorrect. We need to be following a proper diagnosis and prescription of PBM treatment to achieve optimal clinical responses,” he says.
