Laser Therapy in Veterinary Medicine
The editors Ronald J. Riegel, DVM, is the Co-founder of the American Institute of Medical Laser Applications in Marysville, Ohio, USA. John C. Godbold, Jr., DVM, is the Founder of Stonehaven Veterinary Consulting in Jackson, Tennessee, USA.
Laser Therapy in Veterinary Medicine
The History of Laser Therapy
Ronald J. Riegel
American Institute of Medical Laser Applications, Marysville, OH, USA
Various forms of heliotherapy (light therapy) have been practiced around the world for centuries. Physicians and healers in Ancient Greece, Egypt, and Rome - including renowned Greek historian Herodotus in the 6th century B.C. - all realized the benefits of such therapy (Ellinger, 1957). Likewise, the Inca and Assyrian cultures worshiped the sun with the belief that it would bring them health. Around 1500B.C., Indian medical literature described treatments combining herbal medicine with natural sunlight to treat non-pigmented skin. There are records in the Buddhist literature from around 200A.D. and Chinese documentation from the 10th century recording similar therapeutic effects from light.
In the 17th century, Sir Isaac Newton discovered that prisms could disassemble or separate white light, a phenomenon he described in his book Opticks, originally printed in 1704 (Newton, 1704). He was also the first to use the word "spectrum" (Latin for "appearance" or "apparition") in 1671.
Heliotherapy in the Modern World
Niels Ryberg Finsen, a Faroese physician and scientist of Icelandic descent, is widely regarded as the original proponent of phototherapy. In 1903, he was awarded the Nobel Prize in Medicine and Physiology for the successful treatment of diseases using phototherapy; specifically, lupus vulgaris, a skin infection caused by Mycobacterium tuberculosis (Nobel Prize, 2014b). He also famously utilized ultraviolet light to treat smallpox lesions (Nobel Lectures, 1967).
Shortly thereafter, in 1916, Albert Einstein postulated the theory of lasers to support his Theory of Relativity. First, Einstein proposed that an excited atom in isolation can return to a lower energy state by emitting photons, a process he termed "spontaneous emission." Spontaneous emission sets the scale for all radiative interactions, such as absorption and stimulated emission. Atoms will only absorb photons of the correct wavelength; the photon disappears and the atom goes to a higher-energy state, setting the stage for spontaneous emission. Second, his theory predicted that as light passes through a substance, it stimulates the emission of more light (Hilborn, 1982).
Einstein hypothesized that photons prefer to travel together in the same state. If one has a large collection of atoms containing a great deal of excess energy, they will be ready to emit photons randomly. If a stray photon of the correct wavelength passes by (or, in the case of a laser, is fired at) an atom already in an excited state, its presence will stimulate the atom to release its photons early. The new photons will then travel in the same direction as the original stray photon, with identical frequency and phase. A cascading effect ensues: as the identical photons move through other atoms, ever more photons are emitted (Pais, 1982).
The Laser is Born
On May 16, 1960, Theodore Maiman produced the first ruby laser at the Hughes Aircraft Research Laboratory in Malibu, California, basing his new creation on Albert Einstein's explanation of stimulated emission of radiation, coupled with Townes' and Schawlow's 1958 work with optical masers (Schawlow and Townes, 1958; Itzkan and Drake, 1997).
Several years after the invention of the laser, Dr. Endre Mester - considered the founding father of laser therapy - became the first to experimentally document the healing effects of lasers. Because he used mice as his experimental model, this is also the first documented use of lasers to accelerate healing in veterinary medicine (Mester et al. , 1967). His experiments would also later prove that the acceleration of healing was a s