Appropriate laser eye protection (LEP) devices must be worn within the nominal hazard zone (NHZ) when working with Class 3b and Class 4 lasers or laser systems when engineering or procedural and administrative controls are not practicable. However, if analysis demonstrates that the maximum permissible exposure (MPE) will not be exceeded due to an extremely short NHZ, then LEP may not be required, if confirmed in consultation with the Laser Safety Officer (LSO). This could occur due to laser beam emission characteristics (e.g. highly divergent beam), restrictions placed on the use of the laser or laser systems (e.g. limited open or enclosed beam path) or other factors.

Laser protective eyewear is usually not required for Class 2 or Class 3R lasers or laser systems, except in conditions where intentional long-term (>0.25 seconds) direct viewing is required. Eyewear must be specifically selected to withstand either direct or diffusely scattered beams and shall meet all provisions of ANSI Z87.1-1989. (4.6.2.3)

Eyewear must be inspected before each use, cleaned periodically and replaced if necessary, to maintain the eyewear in good condition. Contact the LSO for assistance in selecting protective eyewear.

This highest risk for accidental injury occurs during laser alignments. See laser alignment procedures.

Factors in selecting appropriate eyewear:
  1. Laser power and /or pulse energy
  2. Wavelength(s) of laser output
  3. Potential for multi-wavelength operation
  4. Radiant exposure or irradiance levels for which protection (worst case) is required
  5. Exposure time criteria
  6. Maximum permissible exposure (MPE)
  7. Optical density requirement of eyewear filters at laser output wavelength
  8. Angular dependence of protection afforded
  9. Visible light transmission requirement and assessment of the effect of the eyewear on the ability to perform tasks while wearing the eyewear
  10. Need for side-shield protection and maximum peripheral vision 
requirement
  11. Radiant exposure or irradiance and the corresponding time factors at which laser safety filter characteristics change occurs, including transient 
bleaching especially for ultra-short pulse lengths
  12. Need for prescription glasses
  13. Comfort and fit
  14. Degradation of filter media, such as photo bleaching
  15. Strength of materials (resistance to mechanical trauma and shock)
  16. Capability of the front surface to produce a hazardous specular reflection
  17. Requirement for anti-fogging design or coatings

Filters used in the construction of laser safe eye protection (LEP) all have physical damage thresholds that may be exceeded under certain conditions, e.g. ultrashort, high peak power and high pulse repetition laser systems. Consult with the LSO and laser eyewear manufacturers when selecting eyewear for these lasers. LEP may also be inadequate to protect the user from serious ocular exposure from high power, multi-kilowatt laser beams.

Manufacturers of Laser Eyewear - This list is provided as a reference only and should not be considered as an endorsement of any particular company or product, by the University of Virginia.
Kentek
Thor Labs
Laservision

 
 
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