As discussed earlier, different wavelengths interact with the body in different ways. We should understand that the same applies to the protective lenses we use. For example, we should not use a pair of safety glasses that are rated to protect against a HeNe laser @ 632 nm when we are using a Ar-Ion laser @ 488 nm. The first thing to take into account when choosing safety glasses is WAVELENGTH.
	We must also take into account that even though we may have chosen the proper protection for a certain wavelength, lenses do not filter out all of the light that may be incident upon them, and all lenses are not rated the same. This is where OPTICAL DENSITY (OD) comes into play. The OD is defined by the ANSI Z136.1 as the logarithm to the base ten of the reciprocal of the transmittance: Dl = - log10 tl where tl is the transmittance.
	Both the wavelength and the OD must be labeled on either the temple for glasses, or on the frame, for goggles. Remember that in certain applications, as in the use of powerful Class IV lasers, certain protective lenses are not meant as a permanent protective shield. For example, in the use of Class IV CO2 lasers @ 10,600 nm, the protective lens only provides sufficient protection to allow immediate movement away from the beam. If the operator remains in the path of the beam, the beam will burn through the lens very quickly.

 

	The selection of proper protective eyewear is of paramount importance when considering eye safety. The eyewear not only must provide protection from frontal and temple exposures, but it should also be comfortable. If the glasses are not comfortable, they will not be worn. Today's manufacturers have tried to keep this in mind in designing the new generation of laser safety eyewear. Today's glasses are not only comfortable and lightweight, but they are stylish and may be ordered with prescription lenses.
	All protective eyewear must be inspected before each use to ensure that it will provide adequate protection. Prior to using a pair of laser safety glasses, the lenses must be inspected for any deep scratches or grooves. If any are found, the eyewear is not to be used. The frame should also be inspected at this time. Check for missing or loose temple screws and ensure that the glasses comfortably fit your face. It is most important to remember to check that the eyewear will provide the proper protection for the wavelength of concern.
	Below are illustrations of various types of laser safety eyewear available. Each type has particular pros and cons. It is the responsibility of the Authorized Laser User to decide which type of eyewear will perform best for his or her workers.
	There are literally hundreds of manufacturers of laser safety eye wear. Included on the links page at the end of this training is a list of some of them.