Mar 17, 2017: Many types of light therapies have been used in the past to give relief to people recovering from injury through infra-red irradiation. Light therapy has been used for years to affect a patient’s state of mind and provide relief from depression.
Although, few studies have investigated the role of light in pain relief, scientific studies of the neurological effects of light therapy is still at an early stage.
The University of Arizona has studied the effects of LED light theray, and taken a step forward towards the potential use of light as a treatment for some forms of chronic pain, by studing the impact of visible-spectrum light from LEDs on the sensory thresholds in rats. Researchers have also studied light’s influence on experimental neuropathic pain.
The study found that when rats with neuropathic pain were put under green LED light from a 525-nm LED, they showed tolerance for thermal and tactile stimulus compared to the rats that were not put under green LED light. The study was reported in the journal Pain.
Visual perception of the green wavelengths
One group of rats were exposed to white light that passed through contact lenses allowing the green part of the spectrum to pass through, showed beneficial effects, while another group wearing opaque lenses and saw no light at all did not show any effects.
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“We tried several other wavelengths, and in the paper we reported that blue light also had some analgesic action, but the effect was most pronounced with the green illumination,” commented Mohab Ibrahim of UA’s Banner-University Medical Center Tucson. “And whatever is happening, it’s happening through the visual system.”
The project experimented with different light intensities and different exposure times. The findings stated that light intensity of between 4 and 100 lux showed a possible sweet spot—lower than that the illumination was too weak. However, anything higher was bright enough to cause negative effects by irritating the rat’s visual system.
An initial test to see the effects on humans was also been carried out, through an approved small-scale double-blind trial on patients attending Ibrahim’s clinic suffering from fibromyalgia, or chronic pain around the joints. The initial response was positive on the patients.
Future clinical trials
“Patients receiving treatment with the green light reported significant reduction in their pain compared to the control group,” said Ibrahim. “However, this is not enough data to draw solid statistical conclusions, but the preliminary data are encouraging and we intend to move forward with larger clinical trials.”
What role the visual system plays in pain relief will further studied. However, one theory related to a stimulated increase in production of enkephalins, is known to be involved in the regulation of an animal’s response to harmful stimuli. The rats exposed to the green light were also found to have elevated levels of enkephalins in the spinal chord.