However, eye protection is needed while using Class 3B or Class 4 type lasers to prevent harmful exposure from reflected and scattered laser beams. The ability of eye wear to filter the laser beam is expressed in terms of optical density. Optical density, type of laser, and visibility required are all important factors in the selection of protective eye wear. Protective eye wear may not provide the same degree of protection for infrared as for visible light and ultraviolet laser beams. Goggles with side shields are preferred because they provide protection against back reflection and side entrance of stray laser beams.
Plastic lenses are light weight and can be molded into comfortable shapes.
UV radiation which can darken the lens or decrease its ability to absorb laser energy. Alignment eye wear is used for low power visible laser beams. Alignment eye wear should not be worn during the operation of high power or invisible laser beams. Instead, safety eye wear that provides adequate protection should be worn. The potential for skin damage depends on the type of laser, power of the laser beam, and the duration of exposure.