Keeping Up on Skin Penetration of Low-Level Laser Light Research

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Editor’s note: According to the AAEP horse owner survey, the top three things that horse owners want from vets are 24/7 coverage, a veterinarian who values them and their horse and communicates well, and a practitioner who keeps up with medical advances. With that in mind, regular installments of Keeping Up will headline recent information to keep you abreast of research and advances in the equine medical community, with some business twists added on.

Credit: Thinkstock When hair was still present, energy penetration was greater for lighter-colored hair than dark.

Credit: Thinkstock When hair was still present, energy penetration was greater for lighter-colored hair than dark.

Skin Penetration of Low-Level Laser Light

Horse owners and veterinarians attempt a variety of treatment modalities to improve the outcomes of lameness associated with flexor tendon injuries. One method of treatment involves applying low-level laser light to areas of inflammation. There is controversy surrounding whether this degree of laser light is able to penetrate equine skin. K.F. Duesterdieck-Zellmer, et al, evaluated this issue and reported their findings in Ex vivo penetration of low-level laser light through equine skin and flexor tendonspublished in Am J Vet Res. 2016 Sep;77(9):991-9.

Wavelengths of 800-970 nm from a therapeutic laser were used to assess percentage of energy penetration into the SDFT (superficial digital flexor tendon) or DDFT (deep digital flexor tendon) in 19 equine cadaver cannon bone areas. The tests were applied over various conditions:

  • Before clipping hair over the skin
  • After clipping hair over the skin
  • After shaving hair over the skin
  • Before shaving hair over the SDFT and DDFT
  • After shaving hair over the SDFT and DDFT

Interestingly, when hair was still present, energy penetration was greater for lighter-colored hair than dark. Energy penetration improved when hair was either clipped or shaved, with light skin allowing the most penetration with 800 nm wavelengths. Medium and dark skin had best penetration with 970 nm wavelengths. Not surprisingly, the thicker the skin, the less the penetration.

The study concluded: “Most laser energy directed through equine skin was absorbed or scattered by the skin.” Skin preparation, color and thickness as well as wavelength used are all elements that affect low-laser light penetration.

Take-Home Message

When using low-laser lights, this type of study might help you determine the animals that will have the greatest penetration of the light, and you can reference this study to your clients for case selection.

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