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Laser-Aided Healing

Clinician's Brief (Capsule)


May 2015

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Far-infrared (FIR) radiation comprises non-visible electromagnetic waves with wavelengths of 3–1000 µm. Infrared radiation transfers energy to surrounding tissues and can be perceived as heat through skin thermoreceptors. In this study, 18 rats were divided into 3 equal groups: 1) nerve injury without FIR biostimulation; 2) nerve injury with FIR biostimulation; and 3) noninjured controls. Rats in groups 1 and 2 had the sciatic nerve surgically transected, then sutured to itself. In control rats, the nerve was approached but not transected.

Rats were irradiated for 30 minutes 5 times per week for 2 weeks after the second postoperative day. Nerve function was assessed by dipping the feet in ink and assessing gait at weekly intervals following surgery. The rats were then euthanized, the gastrocnemius muscles weighed, and the sciatic nerves dissected and histologically compared.

…evidence is compelling for using various forms of light therapy…

Wound-healing at the site of sutured skin was found to occur faster and hair regrowth to be denser in treated rats. In addition, the untreated nerve injury group experienced significantly slower nerve recovery than the FIR-treated group. Gastrocnemius muscle evaluation showed reduced atrophy in the FIR-treated group. Histologically, transverse and longitudinal sections of the sciatic nerve were compared between groups; results showed superior nerve regeneration in the FIR-treated group compared with the untreated nerve injury group. FIR radiation therapy accelerated and improved regeneration of injured peripheral nerves in the rats; however, the exact mechanism for improvement needs to be elucidated.


Light therapy, including low-level laser therapy or cold laser, is an up-and-coming form of treatment. Clinical studies, however, are lacking. It is not clear why light of certain wavelengths may work better in different clinical settings, such as the FIR radiation of this study. Future clinical studies must include cats and dogs to be relevant to our practice, but for now, evidence is compelling for using various forms of light therapy in wound management and states of acute or chronic inflammation.—Heather Troyer, DVM, DABVP, CVA


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