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Section XVIII

Laser Safety Eyewear

Enclosure of the laser equipment or the beam path is the preferred method of control. However, when enclosures are not feasible and there is a potential exposure to the beam or reflected beams at levels above the MPE, it may be necessary to wear protective eyewear.

  1. Availability and Use of Laser Safety Eyewear
    • Laser safety eyewear shall be available and worn by laser operators, incident personnel and visitors in laboratories where a Class 3b or Class 4 laser is present and there is a potential exposure to the beam or reflected beams at levels above the MPE.
    • Laser safety eyewear is not required for Class 2 or Class 3R (formally 3a) lasers unless intentional long-term (>.25 seconds) direct viewing is required.
    • The Principal Investigator is responsible for ensuring that the appropriate eyewear is available and worn.
  2. Selecting Laser Safety Eyewear
    • Laser safety eyewear is wavelength specific.
    • The following information is needed to select the appropriate laser safety eyewear:
      1. Wavelength(s)
      2. Mode of operation (continuous wave or pulsed)
      3. Maximum exposure duration (assume worst case scenario)
      4. Maximum irradiance (W/cm2) or radiant exposure (J/cm2)
      5. Maximum permissible exposure (MPE)
      6. Optical density (OD)
    • Contact EHRS for assistance in calculating the MPE and OD and selecting appropriate eyewear.
    • Laser safety eyewear shall be chosen based on the level of protection needed to protect the eyes from a worst case scenario. If several laser safety eyewear products offer sufficient protection, the following factors should also be considered:
      1. Visible light transmission
      2. Effect on color vision
      3. Field of view provided by the design of the eyewear
      4. Reversible bleaching of absorbing media
      5. Need for prescription lenses
      6. Fit and comfort
      7. Impact resistance
    • Types of Laser Safety Eyewear
      1. Glass: Glass laser eyewear is heavier and more costly than plastic, but it provides better visible light transmittance. There are two types of glass lenses, those with absorptive glass filters and those with reflective coatings. Reflective coatings can create specular reflections and the coating can scratch, minimizing the protection level of the eyewear.
      2. Polycarbonate: Polycarbonate laser eyewear is lighter, less expensive and offers higher impact resistance than glass, but allows less visible light transmittance.
      3. Diffuse Viewing Only (DVO): As the name implies, DVO eyewear is to be used when there is a potential for exposure to diffuse reflections only. DVO eyewear may not provide protection from the direct beam or specular reflections.
      4. Alignment Eyewear: Alignment eyewear may be used when aligning low power visible laser beams. Alignment eyewear transmits enough of the specified wavelength to be seen for alignment purposes, but not enough to cause damage to the eyes. Alignment eyewear cannot be used during operation of high power or invisible beams and cannot be used with pulsed lasers.
  3. Laser Safety Eyewear for Multiple Wavelengths
    One pair of laser safety eyewear may not be sufficient when working with tunable or multiple wavelength lasers. Always check the OD and wavelength prior to use. Eyewear with multiband filters and flip-up eyewear are available for some applications.
  4. Laser Safety Eyewear for Ultra-Fast (Femtosecond) Lasers
    Temporary bleaching may occur from high peak irradiances from ultra-fast laser pulses. Contact the manufacturer of the laser safety eyewear for test data to determine if the eyewear will provide adequate protection before using them.
  5. Labeling of Laser Safety Eyewear
    Laser safety eyewear shall be labeled with the optical density and the wavelength(s) the eyewear provides protection for. Additional labeling may be added for quick identification of eyewear in multiple laser laboratories.
  6. Inspection and Cleaning of Laser Safety Eyewear
    Laser safety eyewear should be inspected periodically for the following:
    1. Pitting, crazing, cracking and discoloration of the attenuation material.
    2. Mechanical integrity of the frame.
    3. Light leaks.
    4. Coating damage.
    Follow manufacturers’ instructions when cleaning laser safety eyewear. Use care when cleaning eyewear to avoid damage to absorbing filters or reflecting surface.

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