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OBJECTIVES

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Following completion of this chapter, student will be able to:

  • Identify the different types of light therapy, specifically lasers and light emitting diodes (LEDs).

  • Explain the physical principles used to produce laser light.

  • Contrast the characteristics of the helium neon, gallium arsenide, and gallium aluminum arsenide low-power lasers.

  • Analyze the therapeutic applications of lasers and LEDs in wound and soft-tissue healing as well as edema, inflammation, and pain reduction.

  • Demonstrate the application techniques of low-power lasers and LEDs.

  • Describe the classifications of lasers.

  • Incorporate the safety considerations in the use of lasers.

  • Be aware of the precautions and contraindications for low-power lasers.

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In recent years, there has been significant interest in light therapy as a clinical therapeutic intervention modality. This intervention provides the clinician with the potential of increasing cellular activity at any point during the healing cycle with few known contraindications. In this chapter, we will focus specifically on LASERS (light amplification by stimulated emissions of radiation) and LEDs (light emitting diodes). Einstein in 1916 was the first to postulate the theorems that conceptualized the development of lasers. The first work with amplified electromagnetic radiation dealt with microwave amplification of stimulated emission of radiation (MASER). In 1955, Townes and Schawlow showed that it was possible to produce stimulated emission of microwaves beyond the optical region of the electromagnetic spectrum. This work with stimulated emission soon extended into the optical region of the electromagnetic spectrum, resulting in the development of devices called optical masers. The first working optical maser was constructed in 1960 by Theodore Maiman when he developed the synthetic ruby laser. Other types of lasers were devised shortly afterward. It was not until 1965 that the term laser was substituted for optical masers.1 Lasers have been incorporated into numerous everyday applications that range from audio discs and supermarket scanning to communication and medical applications.2

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  • LASER = Light Amplification by Stimulated Emission of Radiation

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Other light forms that can be used in the therapeutic setting include light emitting diodes and superluminous diodes (SLDs). Light emitting diodes are far newer technology that have some similarities to lasers in the light they produce. However, it is imperative that one understands these light forms are different from each other. Continued research needs to be completed to determine the physiological differences they can induced and their effectiveness in different medical conditions. This chapter deals principally with the application of low-level lasers and LEDs as they are used in the conservative management of medical conditions.

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PHYSICS OF LASERS

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A laser is a form of electromagnetic energy that has wavelengths and frequencies that fall within the infrared and visible light portions of the electromagnetic spectrum.1 Electromagnetic light energy is transmitted through space as waves that contain tiny “energy packets” called photons. Each photon contains a definite amount of energy, depending on its wavelength (color).

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